Tubers, corms and bulbs, oh my!

From: Christopher Rogers <crogers at ecoanalysts.com> on 2010.02.04 at 19:02:07(20545) Hiyer! Irecently had a discussion with few Aroid Oriented Individuals about properterminology for the non-root, subterranean aroid parts. Or to put it anotherway, do plants like Amorphophallus, Arum, Helicodiceros, Typhonium, Colocasia,Ambrosina, and the like have tubers, corms or bulbs? Theanswer is that they have tubers. (Or for dear Julius’ sake, “chubas”).� Abulb is composed of thick, modified leaves, arranged in layers, for foodstorage. An onion is a perfect example. � Acorm is composed entirely of stem tissue. It is literally just an undergroundstem. It has an epidermal layer, a vascular cylinder with phloem and xylem andcentral pith. A corm can also be a starch storage organ, but it still has true stemtissue. This is why a corm has the new foliage growth coming from the top andthe roots coming from the base. Corm examples are Crocus, Cyclamen andGladiolus. A cormel is just a diminutive corm. � Atuber is just parenchyma (with some vascular tissue). It has an epidermal layerwith some subdermal vascular tissue, and all the rest is parenchyma. It isalmost entirely a starch storage organ. This is why the foliage and the rootsall come from the top. Most plants with tubers have them borne on stolons, butthat is not necessary. In Amorphophallus, Arum and Typhonium for example, thestem tissue is all encased in the small bud at the top of the tuber. That budgrows upward into a leaf or two, and outward into roots, with the tuberbeneath. Other tuber examples are potatoes and Sinningia. � Abulbil, in the aroid sense, is just a tuber that forms on leaves or leaf axils.It is an unfortunate term as it obviously leads to confusion. Ireally hope that this is helpful to the Aroid community at large, and I hope itcuts down on some of the confusion surrounding these terms. I am sure Pete,Wilbert, Tom, Julius, The Banta or someone can elucidate further, particularlyas far as tuberous rhizomes or rhizomatic tubers are concerned. Happydays, Christopher HTML +More D.Christopher Rogers SeniorInvertebrate Ecologist/ Taxonomist ((,///////////=======

From: "J. Agoston" <agoston.janos123 at gmail.com> on 2010.02.06 at 12:05:06(20547) Dear Christopher, Cyclamen has a Hypocotyl tuber, it is not a corm, corms have a tunic liker bulbs. Regards, Jan HTML +More 2010/2/4 Christopher Rogers Hiyer! Irecently had a discussion with few Aroid Oriented Individuals about properterminology for the non-root, subterranean aroid parts. Or to put it anotherway, do plants like Amorphophallus, Arum, Helicodiceros, Typhonium, Colocasia,Ambrosina, and the like have tubers, corms or bulbs? Theanswer is that they have tubers. (Or for dear Julius’ sake, “chubas”). Abulb is composed of thick, modified leaves, arranged in layers, for foodstorage. An onion is a perfect example. Acorm is composed entirely of stem tissue. It is literally just an undergroundstem. It has an epidermal layer, a vascular cylinder with phloem and xylem andcentral pith. A corm can also be a starch storage organ, but it still has true stemtissue. This is why a corm has the new foliage growth coming from the top andthe roots coming from the base. Corm examples are Crocus, Cyclamen andGladiolus. A cormel is just a diminutive corm. Atuber is just parenchyma (with some vascular tissue). It has an epidermal layerwith some subdermal vascular tissue, and all the rest is parenchyma. It isalmost entirely a starch storage organ. This is why the foliage and the rootsall come from the top. Most plants with tubers have them borne on stolons, butthat is not necessary. In Amorphophallus, Arum and Typhonium for example, thestem tissue is all encased in the small bud at the top of the tuber. That budgrows upward into a leaf or two, and outward into roots, with the tuberbeneath. Other tuber examples are potatoes and Sinningia. Abulbil, in the aroid sense, is just a tuber that forms on leaves or leaf axils.It is an unfortunate term as it obviously leads to confusion. Ireally hope that this is helpful to the Aroid community at large, and I hope itcuts down on some of the confusion surrounding these terms. I am sure Pete,Wilbert, Tom, Julius, The Banta or someone can elucidate further, particularlyas far as tuberous rhizomes or rhizomatic tubers are concerned. Happydays, Christopher D.Christopher Rogers SeniorInvertebrate Ecologist/ Taxonomist ((,///////////=======

From: "Tom Croat" <Thomas.Croat at mobot.org> on 2010.02.06 at 22:07:45(20549) Dear Christopher: ����������� That is an excellentdistinction that you made for the difference between tuber and corm.� I havealways assumed that the corm was non existent in Araceae since most storageorgans called stems are just a big bag of starch. Tom HTML +More From:aroid-l-bounces@gizmoworks.com [mailto:aroid-l-bounces@gizmoworks.com] On Behalf Of Christopher Rogers Sent: Thursday, February 04, 20101:02 PM To: 'Discussion of aroids' Subject: [Aroid-l] Tubers, cormsand bulbs, oh my! Hiyer! I recently had a discussion with fewAroid Oriented Individuals about proper terminology for the non-root,subterranean aroid parts. Or to put it another way, do plants likeAmorphophallus, Arum, Helicodiceros, Typhonium, Colocasia, Ambrosina, and thelike have tubers, corms or bulbs? The answer is that they have tubers. (Orfor dear Julius’ sake, “chubas”). A bulb is composed of thick, modifiedleaves, arranged in layers, for food storage. An onion is a perfect example. A corm is composed entirely of stemtissue. It is literally just an underground stem. It has an epidermal layer, avascular cylinder with phloem and xylem and central pith. A corm can also be astarch storage organ, but it still has true stem tissue. This is why a corm hasthe new foliage growth coming from the top and the roots coming from the base.Corm examples are Crocus, Cyclamen and Gladiolus. A cormel is just a diminutivecorm. A tuber is just parenchyma (with somevascular tissue). It has an epidermal layer with some subdermal vasculartissue, and all the rest is parenchyma. It is almost entirely a starch storageorgan. This is why the foliage and the roots all come from the top. Most plantswith tubers have them borne on stolons, but that is not necessary. InAmorphophallus, Arum and Typhonium for example, the stem tissue is all encasedin the small bud at the top of the tuber. That bud grows upward into a leaf ortwo, and outward into roots, with the tuber beneath. Other tuber examples arepotatoes and Sinningia. A bulbil, in the aroid sense, is just atuber that forms on leaves or leaf axils. It is an unfortunate term as itobviously leads to confusion. I really hope that this is helpful to theAroid community at large, and I hope it cuts down on some of the confusionsurrounding these terms. I am sure Pete, Wilbert, Tom, Julius, The Banta orsomeone can elucidate further, particularly as far as tuberous rhizomes orrhizomatic tubers are concerned. Happy days, Christopher D. Christopher Rogers Senior Invertebrate Ecologist/ Taxonomist ((,///////////=======

From: "Ertelt, Jonathan B" <jonathan.ertelt at vanderbilt.edu> on 2010.02.08 at 20:02:42(20553) Greetings, While I would agree that the recent discourse on tubers vs. corms certainly makes clear an excellent distinction, the difficulty I have with it is that this is not what many sources suggest. Several examples: From Swartz, D. 1971. Collegiate Dictionary of Botany: Tuber – a relatively short thickened rhizome with numerous buds as in the potato; a subterranean stem which is shorter and thicker than the root stock Corm – a solid fleshy underground base of a stem, usually somewhat spherical in shape, covered with thin membranes. It serves for storage of reserve food materials and resembles a bulb in appearance but not in structure From Radford, A.E., Ahles,H.E., & Bell, C. R.. 1964. Manual of the Vascular Flora of the Carolinas: Tuber – a fleshy enlarged portion of rhizome or stolon with only vestigial scales; true tubers found in the Solanaceae Corm – a bulb-like structure in which the fleshy portion is predominantly stem tissue covered by membranous scales And within the text, from Family 31. Araceae (The family description begins) Perennial herbs from rhizomes or corms... From Radford, A.E., Dickison, W.C., Massey, J.R., Bell, C.R. 1974. Vascular Plant Systematics: Tuber – a thick storage stem, usually not upright Corm - the enlarged, solid, fleshy base of a stem with scales; an upright underground storage stem And from Stearn, W.T. 1983 (3rd Edition, revised) Botanical Latin: Tuber – (in part) tuber large globose or irregular, with flesh whitish bitter Corm - literally ‘a trunk’; - for the solid bulb-like stem-base of monocotyledons, the older authors, e.g. Ker-Gawler, used bulbo-tuber; cormus magnus sub-globosus 5 cm. crassus tunicis brunneis membranaceis, corm large almost globose 5 cm. thick, with tunics brown membranous. There is no debate regarding bulbs – a bulb is an underground storage structure comprised of thickened foreshortened leaves all attached to a basal stem disc. But with the real debate at hand, whether what we are looking at, definitely a modified stem of some sort (and the sort is not uniform across all the genera mentioned, nor even always within the same genus) is corm or tuber is I would say still up for debate, depending on who’s definition of the terms one wants or decides to choose. As for rhizomatic(?) (rhizomatous) tubers or tuberous rhizomes, I’m sure others may have a more serious vested interest in this debate, but to me they’re both one type of stem serving as an adjective for another type of stem, and which one chooses to put first is more a matter of semantics, or else simply which aspect of the stems growth one notes as being more significant, or maybe simply which was noted first. This of course is not the case with the example of a sweet potato, which is a tuberous root, i.e a root structure that closely resembles a tuber. Though by no means the only difference, a major part of the difference here is how the vascular tissue is arranged. Between stem type ‘a’ and stem type ‘b’ the challenge may be a bit more difficult because in both of them the vascular tissue conforms to the stem type arrangement. This vascular tissue is amply present in both, perhaps even more so in the tuber since tubers typically have more than one eye, i.e a new stem starting point. And although I am sure that there are examples within the aroid genera mentioned, since the Sinningia genus (Gesneriaceae) was also cited for tubers and I am even more well acquainted with these I would point out that roots grow out from many different areas of the tubers, definitely not just from the top. Not to purposely remuddy the waters, but there it is. Happy days, and good growing. Jonathan HTML +More On 2/4/10 1:02 PM, "Christopher Rogers" wrote: Hiyer! I recently had a discussion with few Aroid Oriented Individuals about proper terminology for the non-root, subterranean aroid parts. Or to put it another way, do plants like Amorphophallus, Arum, Helicodiceros, Typhonium, Colocasia, Ambrosina, and the like have tubers, corms or bulbs? The answer is that they have tubers. (Or for dear Julius’ sake, “chubas”). A bulb is composed of thick, modified leaves, arranged in layers, for food storage. An onion is a perfect example. A corm is composed entirely of stem tissue. It is literally just an underground stem. It has an epidermal layer, a vascular cylinder with phloem and xylem and central pith. A corm can also be a starch storage organ, but it still has true stem tissue. This is why a corm has the new foliage growth coming from the top and the roots coming from the base. Corm examples are Crocus, Cyclamen and Gladiolus. A cormel is just a diminutive corm. A tuber is just parenchyma (with some vascular tissue). It has an epidermal layer with some subdermal vascular tissue, and all the rest is parenchyma. It is almost entirely a starch storage organ. This is why the foliage and the roots all come from the top. Most plants with tubers have them borne on stolons, but that is not necessary. In Amorphophallus, Arum and Typhonium for example, the stem tissue is all encased in the small bud at the top of the tuber. That bud grows upward into a leaf or two, and outward into roots, with the tuber beneath. Other tuber examples are potatoes and Sinningia. A bulbil, in the aroid sense, is just a tuber that forms on leaves or leaf axils. It is an unfortunate term as it obviously leads to confusion. I really hope that this is helpful to the Aroid community at large, and I hope it cuts down on some of the confusion surrounding these terms. I am sure Pete, Wilbert, Tom, Julius, The Banta or someone can elucidate further, particularly as far as tuberous rhizomes or rhizomatic tubers are concerned. Happy days, Christopher D. Christopher Rogers Senior Invertebrate Ecologist/ Taxonomist ((,///////////======

From: "E.Vincent Morano" <ironious2 at yahoo.com> on 2010.02.08 at 23:02:47(20554) All good info! But this begs the question. What then is a rhizome? it doesnt look like tuber corm nor bulb. I refuse to participate in the in the recession. --- On Thu, 2/4/10, Christopher Rogers wrote: HTML +More From: Christopher Rogers Subject: [Aroid-l] Tubers, corms and bulbs, oh my! To: "'Discussion of aroids'" Date: Thursday, February 4, 2010, 11:02 AM Hiyer! I recently had a discussion with few Aroid Oriented Individuals about proper terminology for the non-root, subterranean aroid parts. Or to put it another way, do plants like Amorphophallus, Arum, Helicodiceros, Typhonium, Colocasia, Ambrosina, and the like have tubers, corms or bulbs? The answer is that they have tubers. (Or for dear Julius’ sake, “chubas”). A bulb is composed of thick, modified leaves, arranged in layers, for food storage. An onion is a perfect example. A corm is composed entirely of stem tissue. It is literally just an underground stem. It has an epidermal layer, a vascular cylinder with phloem and xylem and central pith. A corm can also be a starch storage organ, but it still has true stem tissue. This is why a corm has the new foliage growth coming from the top and the roots coming from the base. Corm examples are Crocus, Cyclamen and Gladiolus. A cormel is just a diminutive corm. A tuber is just parenchyma (with some vascular tissue). It has an epidermal layer with some subdermal vascular tissue, and all the rest is parenchyma. It is almost entirely a starch storage organ. This is why the foliage and the roots all come from the top. Most plants with tubers have them borne on stolons, but that is not necessary. In Amorphophallus, Arum and Typhonium for example, the stem tissue is all encased in the small bud at the top of the tuber. That bud grows upward into a leaf or two, and outward into roots, with the tuber beneath. Other tuber examples are potatoes and Sinningia. A bulbil, in the aroid sense, is just a tuber that forms on leaves or leaf axils. It is an unfortunate term as it obviously leads to confusion. I really hope that this is helpful to the Aroid community at large, and I hope it cuts down on some of the confusion surrounding these terms. I am sure Pete, Wilbert, Tom, Julius, The Banta or someone can elucidate further, particularly as far as tuberous rhizomes or rhizomatic tubers are concerned. Happy days, Christopher D. Christopher Rogers Senior Invertebrate Ecologist/ Taxonomist ((,///////////=======

From: ExoticRainforest <Steve at exoticrainforest.com> on 2010.02.10 at 09:27:42(20558) A rhizome is a stem that runs eitheralong or just beneath the surface of the soil. For those that don't have a good grasp on the term stem, a stem is thebase, central axis and main support of a plant normally divided intonodes and internodes. The nodes often produce a leaf in the axil ofwhich they produce roots and hold buds which may grow into shoots ofvarious forms. The stem's roots anchor the plant either to the ground,a tree or to a rock and may spread as a repent rhizome meaning it creeps across the soil. Thestem may either grow above ground, underground or partially above thesoil. As Christopher stated the specialized stem forms are called acorm, tuber or bulb but the only term that is applicable to an aroid istuber. That info was verified courtesy of Dr. Croat for an article I will havein the next issue of Aroideana. Steve HTML +More www.ExoticRainforest.com E.Vincent Morano wrote: All good info! But this begs the question. What then is arhizome? it doesnt look like tuber corm nor bulb. I info/aroid-l --------------080907080207090400080905

From: "J. Agoston" <agoston.janos123 at gmail.com> on 2010.02.10 at 16:25:23(20561) Wow Jonathan... I just say that rhizome has allways (year-round) roots, like Iris � germanica. This is complicated. Here we say Achimenes and Oxalis triangularis have rhizome too. But it is incorrect botanically. It is a stem covered with cataphylls which store food and water. But they don't have roots all the time, which is not fulfilling the term of rhizome from my point of view. Oxalis have somtimes thickened taproot, which stores food and water too, and under winter storage the root witheres while the so called rhizome grows from the root's nutrients. It is said that rhizomes started to develope storing cataphylls and with time cataphylls become larger and rhizomes become smaller. Evolutionists say this is how bulbs evolved from rhizome. (Jacob - J�ger - Ohmann: Botanical Compendium) It is now clear that Littonia, Gloriosa, Sandersonia have corms (they re-develope yearly, the buds are on the surface, and have a tunic, even if it is papery). Interestingyl Zantedeschia aethiopica have rhizomes if kept green all year, but have tuber if sent to dormancy, at least in my terms. Normally this plant goes to dormancy in nature so it has a tuber. Moreover tubers and rhizomes send out secondary roots. The primary root dies soon after germination, but first the rhizome and the tuber forms. Botanists, the few who wish to investigate such things are also in constant debate. Cyclamen, Sinningia, Begonia � tuberhybrida develop their tubers from hypocotyl. They can grow bigger and bigger from year to year. But they have roots year round, at least cyclamen have. I suggested for botanists to brain storm a little regarding vegetative storage organs, but they don't find it interesting. They can make more money and reputation with taxonomic researches. I also have debate regarding Corydalis solida. It looks like a corm (re-grows every year, have a papery tunic, eye is on the surface), but it doesn't re-grow from the basal internode as real corms do, it re-grows like a bulb, from inside. We consider it a transition between corm and bulb. As it doesn't have any influence on the market, and it is not insipiring botanists so much remains a mystery. Another unanswered mystery of life. Jan HTML +More Z5a, Hungary --0016e65b60a83ba426047f417b89----==============w01705742499733021=

From: Theodore Held <oppenhauser2001 at gmail.com> on 2010.02.10 at 19:18:10(20564) As everyone who has been on this list for any length of time knows, the actual term for all these structures is "chubas". End of discussion. Ted Held. On Mon, Feb 8, 2010 at 6:02 PM, E.Vincent Morano wrote: HTML +More All good info! But this begs the question. What then is a rhizome? it doesnt look like tuber corm nor bulb. I refuse to participate in the in the recession. --- On Thu, 2/4/10, Christopher Rogers wrote: From: Christopher Rogers Subject: [Aroid-l] Tubers, corms and bulbs, oh my! To: "'Discussion of aroids'" Date: Thursday, February 4, 2010, 11:02 AM Hiyer! I recently had a discussion with few Aroid Oriented Individuals about proper terminology for the non-root, subterranean aroid parts. Or to put it another way, do plants like Amorphophallus, Arum, Helicodiceros, Typhonium, Colocasia, Ambrosina, and the like have tubers, corms or bulbs? The answer is that they have tubers. (Or for dear Julius’ sake, “chubas”). A bulb is composed of thick, modified leaves, arranged in layers, for food storage. An onion is a perfect example. A corm is composed entirely of stem tissue. It is literally just an underground stem. It has an epidermal layer, a vascular cylinder with phloem and xylem and central pith. A corm can also be a starch storage organ, but it still has true stem tissue. This is why a corm has the new foliage growth coming from the top and the roots coming from the base. Corm examples are Crocus, Cyclamen and Gladiolus. A cormel is just a diminutive corm. A tuber is just parenchyma (with some vascular tissue). It has an epidermal layer with some subdermal vascular tissue, and all the rest is parenchyma. It is almost entirely a starch storage organ. This is why the foliage and the roots all come from the top. Most plants with tubers have them borne on stolons, but that is not necessary. In Amorphophallus, Arum and Typhonium for example, the stem tissue is all encased in the small bud at the top of the tuber. That bud grows upward into a leaf or two, and outward into roots, with the tuber beneath. Other tuber examples are potatoes and Sinningia. A bulbil, in the aroid sense, is just a tuber that forms on leaves or leaf axils. It is an unfortunate term as it obviously leads to confusion. I really hope that this is helpful to the Aroid community at large, and I hope it cuts down on some of the confusion surrounding these terms. I am sure Pete, Wilbert, Tom, Julius, The Banta or someone can elucidate further, particularly as far as tuberous rhizomes or rhizomatic tubers are concerned. Happy days, Christopher D. Christopher Rogers Senior Invertebrate Ecologist/ Taxonomist ((,///////////=======

From: "Marek Argent" <abri1973 at wp.pl> on 2010.02.10 at 23:11:55(20565)  Dear Vincent, A rhizome is a stem (erect or creeping) with very shortened internodes. Calla palustris, Anubias spp, Xanthosoma violaceum. And the best it is visible in large Alocasia spp. Here's an example: http://www.wschowa.com/abrimaal/araceum/alocasia/odora.htm Marek HTML +More ----- Original Message ----- From: E.Vincent Morano To: Discussion of aroids Sent: Tuesday, February 09, 2010 12:02 AM Subject: Re: [Aroid-l] Tubers, corms and bulbs, oh my! All good info! But this begs the question. What then is a rhizome? it doesnt look like tuber corm nor bulb. I refuse to participate in the in the recession. --- On Thu, 2/4/10, Christopher Rogers wrote: From: Christopher Rogers Subject: [Aroid-l] Tubers, corms and bulbs, oh my! To: "'Discussion of aroids'" Date: Thursday, February 4, 2010, 11:02 AM Hiyer! I recently had a discussion with few Aroid Oriented Individuals about proper terminology for the non-root, subterranean aroid parts. Or to put it another way, do plants like Amorphophallus, Arum, Helicodiceros, Typhonium, Colocasia, Ambrosina, and the like have tubers, corms or bulbs? The answer is that they have tubers. (Or for dear Julius’ sake, “chubas”). A bulb is composed of thick, modified leaves, arranged in layers, for food storage. An onion is a perfect example. A corm is composed entirely of stem tissue. It is literally just an underground stem. It has an epidermal layer, a vascular cylinder with phloem and xylem and central pith. A corm can also be a starch storage organ, but it still has true stem tissue. This is why a corm has the new foliage growth coming from the top and the roots coming from the base. Corm examples are Crocus, Cyclamen and Gladiolus. A cormel is just a diminutive corm. A tuber is just parenchyma (with some vascular tissue). It has an epidermal layer with some subdermal vascular tissue, and all the rest is parenchyma. It is almost entirely a starch storage organ. This is why the foliage and the roots all come from the top. Most plants with tubers have them borne on stolons, but that is not necessary. In Amorphophallus, Arum and Typhonium for example, the stem tissue is all encased in the small bud at the top of the tuber. That bud grows upward into a leaf or two, and outward into roots, with the tuber beneath. Other tuber examples are potatoes and Sinningia. A bulbil, in the aroid sense, is just a tuber that forms on leaves or leaf axils. It is an unfortunate term as it obviously leads to confusion. I really hope that this is helpful to the Aroid community at large, and I hope it cuts down on some of the confusion surrounding these terms. I am sure Pete, Wilbert, Tom, Julius, The Banta or someone can elucidate further, particularly as far as tuberous rhizomes or rhizomatic tubers are concerned. Happy days, Christopher D. Christopher Rogers Senior Invertebrate Ecologist/ Taxonomist ((,///////////=======

From: "Daniel Devor" <plantguy at zoominternet.net> on 2010.02.10 at 23:40:40(20566)  Not that I'm all that concerned with the exact botanical term that accurately describes the 'tater our Amorphs grow from, but surely we can all agree that if we unpot or dig up our Amorph species carefully it is not at all uncommon to see roots coming from other than the top of the underground thingy. I find it rather common for the long rhizomatous growths to have roots coming out all along them, at least when I pay attention. So, does this mean that the original description for a tuber posited below needs to be revised or we need to rethink what we call it? It seems the definition is not so simple for the botanists out there. Since I learned it as a tuber when I first got my original A. konjac many years ago I'm perfectly happy with that term, but it seems from the posts it is a bit of a hornets nest. Dan HTML +More Gibsonia, PA where we got a nice 75cm coating of snow in the past 5 days....spring truly was 6 weeks away :o) ----- Original Message ----- From: Ertelt, Jonathan B To: Discussion of aroids Sent: Monday, February 08, 2010 3:02 PM Subject: Re: [Aroid-l] Tubers, corms and bulbs, oh my! Greetings, While I would agree that the recent discourse on tubers vs. corms certainly makes clear an excellent distinction, the difficulty I have with it is that this is not what many sources suggest. Several examples: From Swartz, D. 1971. Collegiate Dictionary of Botany: Tuber – a relatively short thickened rhizome with numerous buds as in the potato; a subterranean stem which is shorter and thicker than the root stock Corm – a solid fleshy underground base of a stem, usually somewhat spherical in shape, covered with thin membranes. It serves for storage of reserve food materials and resembles a bulb in appearance but not in structure From Radford, A.E., Ahles,H.E., & Bell, C. R.. 1964. Manual of the Vascular Flora of the Carolinas: Tuber – a fleshy enlarged portion of rhizome or stolon with only vestigial scales; true tubers found in the Solanaceae Corm – a bulb-like structure in which the fleshy portion is predominantly stem tissue covered by membranous scales And within the text, from Family 31. Araceae (The family description begins) Perennial herbs from rhizomes or corms... From Radford, A.E., Dickison, W.C., Massey, J.R., Bell, C.R. 1974. Vascular Plant Systematics: Tuber – a thick storage stem, usually not upright Corm - the enlarged, solid, fleshy base of a stem with scales; an upright underground storage stem And from Stearn, W.T. 1983 (3rd Edition, revised) Botanical Latin: Tuber – (in part) tuber large globose or irregular, with flesh whitish bitter Corm - literally ‘a trunk’; - for the solid bulb-like stem-base of monocotyledons, the older authors, e.g. Ker-Gawler, used bulbo-tuber; cormus magnus sub-globosus 5 cm. crassus tunicis brunneis membranaceis, corm large almost globose 5 cm. thick, with tunics brown membranous. There is no debate regarding bulbs – a bulb is an underground storage structure comprised of thickened foreshortened leaves all attached to a basal stem disc. But with the real debate at hand, whether what we are looking at, definitely a modified stem of some sort (and the sort is not uniform across all the genera mentioned, nor even always within the same genus) is corm or tuber is I would say still up for debate, depending on who’s definition of the terms one wants or decides to choose. As for rhizomatic(?) (rhizomatous) tubers or tuberous rhizomes, I’m sure others may have a more serious vested interest in this debate, but to me they’re both one type of stem serving as an adjective for another type of stem, and which one chooses to put first is more a matter of semantics, or else simply which aspect of the stems growth one notes as being more significant, or maybe simply which was noted first. This of course is not the case with the example of a sweet potato, which is a tuberous root, i.e a root structure that closely resembles a tuber. Though by no means the only difference, a major part of the difference here is how the vascular tissue is arranged. Between stem type ‘a’ and stem type ‘b’ the challenge may be a bit more difficult because in both of them the vascular tissue conforms to the stem type arrangement. This vascular tissue is amply present in both, perhaps even more so in the tuber since tubers typically have more than one eye, i.e a new stem starting point. And although I am sure that there are examples within the aroid genera mentioned, since the Sinningia genus (Gesneriaceae) was also cited for tubers and I am even more well acquainted with these I would point out that roots grow out from many different areas of the tubers, definitely not just from the top. Not to purposely remuddy the waters, but there it is. Happy days, and good growing. Jonathan On 2/4/10 1:02 PM, "Christopher Rogers" wrote: Hiyer! I recently had a discussion with few Aroid Oriented Individuals about proper terminology for the non-root, subterranean aroid parts. Or to put it another way, do plants like Amorphophallus, Arum, Helicodiceros, Typhonium, Colocasia, Ambrosina, and the like have tubers, corms or bulbs? The answer is that they have tubers. (Or for dear Julius’ sake, “chubas”). A bulb is composed of thick, modified leaves, arranged in layers, for food storage. An onion is a perfect example. A corm is composed entirely of stem tissue. It is literally just an underground stem. It has an epidermal layer, a vascular cylinder with phloem and xylem and central pith. A corm can also be a starch storage organ, but it still has true stem tissue. This is why a corm has the new foliage growth coming from the top and the roots coming from the base. Corm examples are Crocus, Cyclamen and Gladiolus. A cormel is just a diminutive corm. A tuber is just parenchyma (with some vascular tissue). It has an epidermal layer with some subdermal vascular tissue, and all the rest is parenchyma. It is almost entirely a starch storage organ. This is why the foliage and the roots all come from the top. Most plants with tubers have them borne on stolons, but that is not necessary. In Amorphophallus, Arum and Typhonium for example, the stem tissue is all encased in the small bud at the top of the tuber. That bud grows upward into a leaf or two, and outward into roots, with the tuber beneath. Other tuber examples are potatoes and Sinningia. A bulbil, in the aroid sense, is just a tuber that forms on leaves or leaf axils. It is an unfortunate term as it obviously leads to confusion. I really hope that this is helpful to the Aroid community at large, and I hope it cuts down on some of the confusion surrounding these terms. I am sure Pete, Wilbert, Tom, Julius, The Banta or someone can elucidate further, particularly as far as tuberous rhizomes or rhizomatic tubers are concerned. Happy days, Christopher D. Christopher Rogers Senior Invertebrate Ecologist/ Taxonomist ((,///////////=======

From: "Wilbert Hetterscheid" <hetter at xs4all.nl> on 2010.02.11 at 15:54:44(20570) My 2 cents of superfluous wisdom in this: Tubers in Araceae are condensed stems with food-storage function. Such stems can also be elongate and creeping and then we call then rhizomes. In Araceae rhizome and tuber are two parts of a "continuum". One the one extreme are long creeping rhizomes with numerous long internodes. Condensaton of the internodes give us shorter rhizomes. Reduction of the number of internodes gives us shorter rhizomes (meaning mostly that the decay of older internodes is fast). We may find very short rhizomes (one or two internodes), which because they may be thicker than long, look "tuberous" (Typhonium). Also internodes may be way shorter than their width, which also gives the rhizome a kind of tuberous look (e.g. Arum). And then finally there's rhizomes that produce one internode in a season and at the same time devour the previous internode and they may also decide to grow vertically. That's what we see in e.g. most Amorphophallus and e.g. Sauromatum, several Arisaema. In these genera often few or more species are in fact fully rhizomatous, which goes to show how easily one state changes or reverts to another. In Amorphs there is even a fully genus-exclusive extra: the one-nodal-rhizome (we call tuber) may elongate vertically, not by creating extra nodes but by elongation of the one node present (A. longituberosus and like). My opinion is that "tuber" in Aroids (and in many other families) is more of an "appearance" term, than a truely reliable systematic term. Aroids have stems, which may be creeping, food storing [but not always] and semi- of fully subterranean and then are called rhizome. The shape and structure of a rhizome may be so that it looks like a tuber (and my guess is that "tuber" is an ancient relict word for a food-bringing underground plant part, and as such a human-usage driven term). So, a majority of Amorphs have an upright, subterranean, one-nodal rhizome and we call that a tuber. The best illustration of the "ancient" condition is in Am. coaetaneus, where a chain of swollen, "tuber like" nodes is present. This species has decided not to devour old nodes but keep them intact, so a chain of "tubers" develops (see IAS website under this species) and this chain is in fact again a full scale rhizome. But in the same genus we can also find "normal" rhizomes with many nodes and equally thick all over (A. rhizomatosus, A. hayi). The conditions are therefore evolutionarily interchangeable because they are several sides of the same medal (strange medal THAT is.........). Cheers, Wilbert +More > -----Oorspronkelijk bericht----- > Van: aroid-l-bounces@gizmoworks.com > [mailto:aroid-l-bounces@gizmoworks.com] Namens Marek Argent > Verzonden: donderdag 11 februari 2010 0:12 > Aan: Discussion of aroids > Onderwerp: Re: [Aroid-l] Tubers, corms and bulbs, oh my! > > Dear Vincent, > > A rhizome is a stem (erect or creeping) with very shortened > internodes. > Calla palustris, Anubias spp, Xanthosoma violaceum. > And the best it is visible in large Alocasia spp. > Here's an example: > http://www.wschowa.com/abrimaal/araceum/alocasia/odora.htm > > Marek > > ----- Original Message ----- > From: E.Vincent Morano > To: Discussion of aroids > Sent: Tuesday, February 09, 2010 12:02 AM > Subject: Re: [Aroid-l] Tubers, corms and bulbs, oh my! > > All good info! But this begs the question. What then is a > rhizome? it doesnt look like tuber corm nor bulb. > > > > > > I refuse to participate in the in the recession. > > --- On Thu, 2/4/10, Christopher Rogers > wrote: > > > > From: Christopher Rogers > Subject: [Aroid-l] Tubers, corms and bulbs, oh my! > To: "'Discussion of aroids'" > Date: Thursday, February 4, 2010, 11:02 AM > > > > Hiyer! > > > > I recently had a discussion with few Aroid Oriented > Individuals about proper terminology for the non-root, > subterranean aroid parts. Or to put it another way, do plants > like Amorphophallus, Arum, Helicodiceros, Typhonium, > Colocasia, Ambrosina, and the like have tubers, corms or bulbs? > > > > The answer is that they have tubers. (Or for dear > Juliusà �₠�℠� sake, à �₠�œchubasà �₠� �). > > > > A bulb is composed of thick, modified leaves, arranged > in layers, for food storage. An onion is a perfect example. > > > > A corm is composed entirely of stem tissue. It is > literally just an underground stem. It has an epidermal > layer, a vascular cylinder with phloem and xylem and central > pith. A corm can also be a starch storage organ, but it still > has true stem tissue. This is why a corm has the new foliage > growth coming from the top and the roots coming from the > base. Corm examples are Crocus, Cyclamen and Gladiolus. A > cormel is just a diminutive corm. > > > > A tuber is just parenchyma (with some vascular tissue). > It has an epidermal layer with some subdermal vascular > tissue, and all the rest is parenchyma. It is almost entirely > a starch storage organ. This is why the foliage and the roots > all come from the top. Most plants with tubers have them > borne on stolons, but that is not necessary. In > Amorphophallus, Arum and Typhonium for example, the stem > tissue is all encased in the small bud at the top of the > tuber. That bud grows upward into a leaf or two, and outward > into roots, with the tuber beneath. Other tuber examples are > potatoes and Sinningia. > > > > A bulbil, in the aroid sense, is just a tuber that > forms on leaves or leaf axils. It is an unfortunate term as > it obviously leads to confusion. > > > > I really hope that this is helpful to the Aroid > community at large, and I hope it cuts down on some of the > confusion surrounding these terms. I am sure Pete, Wilbert, > Tom, Julius, The Banta or someone can elucidate further, > particularly as far as tuberous rhizomes or rhizomatic tubers > are concerned. > > > > Happy days, > > Christopher > > > > D. Christopher Rogers > > Senior Invertebrate Ecologist/ Taxonomist > > ((,///////////=======< > > branchiopod@gmail.com > > > > EcoAnalysts, Inc. > > 1.530.383.4798 > > P.O. Box 4098 > > Davis, CA 95616 > > USA > > > > Invertebrate Taxonomy > > Endangered Species > > Ecological Studies > > Bioassessment > > Invasive Species > > Plankton > > Phycology > > IDAHO à �� ℠� CALIFORNIA à �� ℠� MISSOURI à �� ℠� PENNSYLVANIA à �� ℠� VANCOUVER > > WWW.ECOANALYSTS.COM à �� ℠� ECO@ECOANALYSTS.COM > > > > > -----Inline Attachment Follows----- > > > _______________________________________________ > Aroid-L mailing list > Aroid-L@www.gizmoworks.com > http://www.gizmoworks.com/mailman/listinfo/aroid-l > > > > > ________________________________ > > > > > _______________________________________________ > Aroid-L mailing list > Aroid-L@www.gizmoworks.com > http://www.gizmoworks.com/mailman/listinfo/aroid-l > > > > ________________________________ > > > > > > Nie znaleziono virusa w tej wiadomoņ�ci przychodzĆ�cej. > Sprawdzone przez AVG - www.avg.com > Wersja: 8.5.435 / Baza danych wirusà�w: 271.1.1/2678 - > Data wydania: 02/09/10 19:35:00 > > > _______________________________________________ Aroid-L mailing list Aroid-L@www.gizmoworks.com http://www.gizmoworks.com/mailman/listinfo/aroid-l

From: Peter Boyce <phymatarum at googlemail.com> on 2010.02.13 at 09:32:02(20577) I absolutely concur with Wilbert, and would add a further caveat that 'tubers' in aroids are also NOT homologous. For certain they have arisen independently several times over the family's now solidly minimum age of 140 my. Peter +More -----Original Message----- From: aroid-l-bounces@gizmoworks.com [mailto:aroid-l-bounces@gizmoworks.com] On Behalf Of Wilbert Hetterscheid Sent: Thursday, 11 February, 2010 11:55 PM To: 'Discussion of aroids' Subject: Re: [Aroid-l] Tubers, corms and bulbs, oh my! My 2 cents of superfluous wisdom in this: Tubers in Araceae are condensed stems with food-storage function. Such stems can also be elongate and creeping and then we call then rhizomes. In Araceae rhizome and tuber are two parts of a "continuum". One the one extreme are long creeping rhizomes with numerous long internodes. Condensaton of the internodes give us shorter rhizomes. Reduction of the number of internodes gives us shorter rhizomes (meaning mostly that the decay of older internodes is fast). We may find very short rhizomes (one or two internodes), which because they may be thicker than long, look "tuberous" (Typhonium). Also internodes may be way shorter than their width, which also gives the rhizome a kind of tuberous look (e.g. Arum). And then finally there's rhizomes that produce one internode in a season and at the same time devour the previous internode and they may also decide to grow vertically. That's what we see in e.g. most Amorphophallus and e.g. Sauromatum, several Arisaema. In these genera often few or more species are in fact fully rhizomatous, which goes to show how easily one state changes or reverts to another. In Amorphs there is even a fully genus-exclusive extra: the one-nodal-rhizome (we call tuber) may elongate vertically, not by creating extra nodes but by elongation of the one node present (A. longituberosus and like). My opinion is that "tuber" in Aroids (and in many other families) is more of an "appearance" term, than a truely reliable systematic term. Aroids have stems, which may be creeping, food storing [but not always] and semi- of fully subterranean and then are called rhizome. The shape and structure of a rhizome may be so that it looks like a tuber (and my guess is that "tuber" is an ancient relict word for a food-bringing underground plant part, and as such a human-usage driven term). So, a majority of Amorphs have an upright, subterranean, one-nodal rhizome and we call that a tuber. The best illustration of the "ancient" condition is in Am. coaetaneus, where a chain of swollen, "tuber like" nodes is present. This species has decided not to devour old nodes but keep them intact, so a chain of "tubers" develops (see IAS website under this species) and this chain is in fact again a full scale rhizome. But in the same genus we can also find "normal" rhizomes with many nodes and equally thick all over (A. rhizomatosus, A. hayi). The conditions are therefore evolutionarily interchangeable because they are several sides of the same medal (strange medal THAT is.........). Cheers, Wilbert > -----Oorspronkelijk bericht----- > Van: aroid-l-bounces@gizmoworks.com > [mailto:aroid-l-bounces@gizmoworks.com] Namens Marek Argent > Verzonden: donderdag 11 februari 2010 0:12 > Aan: Discussion of aroids > Onderwerp: Re: [Aroid-l] Tubers, corms and bulbs, oh my! > > Dear Vincent, > > A rhizome is a stem (erect or creeping) with very shortened > internodes. > Calla palustris, Anubias spp, Xanthosoma violaceum. > And the best it is visible in large Alocasia spp. > Here's an example: > http://www.wschowa.com/abrimaal/araceum/alocasia/odora.htm > > Marek > > ----- Original Message ----- > From: E.Vincent Morano > To: Discussion of aroids > Sent: Tuesday, February 09, 2010 12:02 AM > Subject: Re: [Aroid-l] Tubers, corms and bulbs, oh my! > > All good info! But this begs the question. What then is a > rhizome? it doesnt look like tuber corm nor bulb. > > > > > > I refuse to participate in the in the recession. > > --- On Thu, 2/4/10, Christopher Rogers > wrote: > > > > From: Christopher Rogers > Subject: [Aroid-l] Tubers, corms and bulbs, oh my! > To: "'Discussion of aroids'" > Date: Thursday, February 4, 2010, 11:02 AM > > > > Hiyer! > > > > I recently had a discussion with few Aroid Oriented > Individuals about proper terminology for the non-root, > subterranean aroid parts. Or to put it another way, do plants > like Amorphophallus, Arum, Helicodiceros, Typhonium, > Colocasia, Ambrosina, and the like have tubers, corms or bulbs? > > > > The answer is that they have tubers. (Or for dear > Juliusà �₠�℠� sake, à �₠�œchubasà �₠� �). > > > > A bulb is composed of thick, modified leaves, arranged > in layers, for food storage. An onion is a perfect example. > > > > A corm is composed entirely of stem tissue. It is > literally just an underground stem. It has an epidermal > layer, a vascular cylinder with phloem and xylem and central > pith. A corm can also be a starch storage organ, but it still > has true stem tissue. This is why a corm has the new foliage > growth coming from the top and the roots coming from the > base. Corm examples are Crocus, Cyclamen and Gladiolus. A > cormel is just a diminutive corm. > > > > A tuber is just parenchyma (with some vascular tissue). > It has an epidermal layer with some subdermal vascular > tissue, and all the rest is parenchyma. It is almost entirely > a starch storage organ. This is why the foliage and the roots > all come from the top. Most plants with tubers have them > borne on stolons, but that is not necessary. In > Amorphophallus, Arum and Typhonium for example, the stem > tissue is all encased in the small bud at the top of the > tuber. That bud grows upward into a leaf or two, and outward > into roots, with the tuber beneath. Other tuber examples are > potatoes and Sinningia. > > > > A bulbil, in the aroid sense, is just a tuber that > forms on leaves or leaf axils. It is an unfortunate term as > it obviously leads to confusion. > > > > I really hope that this is helpful to the Aroid > community at large, and I hope it cuts down on some of the > confusion surrounding these terms. I am sure Pete, Wilbert, > Tom, Julius, The Banta or someone can elucidate further, > particularly as far as tuberous rhizomes or rhizomatic tubers > are concerned. > > > > Happy days, > > Christopher > > > > D. Christopher Rogers > > Senior Invertebrate Ecologist/ Taxonomist > > ((,///////////=======< > > branchiopod@gmail.com > > > > EcoAnalysts, Inc. > > 1.530.383.4798 > > P.O. Box 4098 > > Davis, CA 95616 > > USA > > > > Invertebrate Taxonomy > > Endangered Species > > Ecological Studies > > Bioassessment > > Invasive Species > > Plankton > > Phycology > > IDAHO à �� ℠� CALIFORNIA à �� ℠� MISSOURI à �� ℠� PENNSYLVANIA à �� ℠� VANCOUVER > > WWW.ECOANALYSTS.COM à �� ℠� ECO@ECOANALYSTS.COM > > > > > -----Inline Attachment Follows----- > > > _______________________________________________ > Aroid-L mailing list > Aroid-L@www.gizmoworks.com > http://www.gizmoworks.com/mailman/listinfo/aroid-l > > > > > ________________________________ > > > > > _______________________________________________ > Aroid-L mailing list > Aroid-L@www.gizmoworks.com > http://www.gizmoworks.com/mailman/listinfo/aroid-l > > > > ________________________________ > > > > > > Nie znaleziono virusa w tej wiadomoņ�ci przychodzĆ�cej. > Sprawdzone przez AVG - www.avg.com > Wersja: 8.5.435 / Baza danych wirusà�w: 271.1.1/2678 - > Data wydania: 02/09/10 19:35:00 > > > _______________________________________________ Aroid-L mailing list Aroid-L@www.gizmoworks.com http://www.gizmoworks.com/mailman/listinfo/aroid-l _______________________________________________ Aroid-L mailing list Aroid-L@www.gizmoworks.com http://www.gizmoworks.com/mailman/listinfo/aroid-l

From: Hannon <othonna at gmail.com> on 2010.02.13 at 10:31:30(20579) Thanks to Wilbert for a very good synopsis of 'compact rootstocks' or tubers in Araceae. As a first time Aroid-Ler and longtime aroider I would like to offer a few comments. I think what Wilbert elaborates here makes perfect sense. My only quibble is that if we make no use of existing descriptive terminology then we use more words than we need to to describe things, or we use words that have imprecise or vague meanings. If all these structures are rhizomes or (apparently) derived evolutionarily from rhizomes, that is very useful as a concept. Yet within this scheme there are structures that can be differentiated, if arbitrarily, into more narrowly defined notions such as tubers, rhizomes and corms. Some of us are weary of any confining definitions altogether. In the case of rootstocks especially it is difficult to imagine any taxonomy that could capture and discretely name the different types found in nature. In fact it has not been done. Still, it seems to me that a corm is something quite distinct, even if its origins are betrayed by peculiar congeners, as in Wilbert's Amorphophallus example. Any modular unit that may resemble a tuber or bulb and _replaces itself each growing season_ can rightfully be called a corm, regardless of the number of nodes/internodes involved or features of tunics vs. naked flesh. Annual replacement is the key trait of a corm. Other families exhibiting "true" corms that are replaced annually (sources in the botanical literature give inconsistent definitions) are the iris family (Gladiolus, Crocus, etc.), Themidaceae (Brodiaea, Milla, etc.) and some Cyanastraceae/Tecophilaeaceae. "Chains of tubers" can be found in Dierama and probably others and perhaps similar ontogenic processes have been at work in these families. As far as I know the rootstocks of these plants have traditionally, in botany, been labeled "corm" and not tuber or bulb. This concise designation continues to serve a useful purpose for the scientist and layman alike. As Wilbert indicates, we have "traditionally" called the tuber-like structures in aroids, well, tubers. If we say there is only a morphological continuum, or that all the rootstock types in a group are basically rhizomes, then clarification and elucidation are sacrificed. Dylan Hannon +More On 11/02/2010, Wilbert Hetterscheid wrote: > My 2 cents of superfluous wisdom in this: > > Tubers in Araceae are condensed stems with food-storage function. Such stems can also be elongate and creeping and then we call then rhizomes. In Araceae rhizome and tuber are two parts of a "continuum". One the one extreme are long creeping rhizomes with numerous long internodes. Condensaton of the internodes give us shorter rhizomes. Reduction of the number of internodes gives us shorter rhizomes (meaning mostly that the decay of older internodes is fast). We may find very short rhizomes (one or two internodes), which because they may be thicker than long, look "tuberous" (Typhonium). Also internodes may be way shorter than their width, which also gives the rhizome a kind of tuberous look (e.g. Arum). And then finally there's rhizomes that produce one internode in a season and at the same time devour the previous internode and they may also decide to grow vertically. That's what we see in e.g. most Amorphophallus and e.g. Sauromatum, several Arisaema. In these genera oft en few or more species are in fact fully rhizomatous, which goes to show how easily one state changes or reverts to another. In Amorphs there is even a fully genus-exclusive extra: the one-nodal-rhizome (we call tuber) may elongate vertically, not by creating extra nodes but by elongation of the one node present (A. longituberosus and like). > > My opinion is that "tuber" in Aroids (and in many other families) is more of an "appearance" term, than a truely reliable systematic term. Aroids have stems, which may be creeping, food storing [but not always] and semi- of fully subterranean and then are called rhizome. The shape and structure of a rhizome may be so that it looks like a tuber (and my guess is that "tuber" is an ancient relict word for a food-bringing underground plant part, and as such a human-usage driven term). > > So, a majority of Amorphs have an upright, subterranean, one-nodal rhizome and we call that a tuber. The best illustration of the "ancient" condition is in Am. coaetaneus, where a chain of swollen, "tuber like" nodes is present. This species has decided not to devour old nodes but keep them intact, so a chain of "tubers" develops (see IAS website under this species) and this chain is in fact again a full scale rhizome. But in the same genus we can also find "normal" rhizomes with many nodes and equally thick all over (A. rhizomatosus, A. hayi). The conditions are therefore evolutionarily interchangeable because they are several sides of the same medal (strange medal THAT is.........). > > Cheers, > Wilbert > > > > _______________________________________________ Aroid-L mailing list Aroid-L@www.gizmoworks.com http://www.gizmoworks.com/mailman/listinfo/aroid-l

From: ExoticRainforest <Steve at exoticrainforest.com> on 2010.02.13 at 21:02:20(20585) Thanks Dylan! I have been trying to do a fair amount of research to better understandall these terms for the past 6 weeks. I corresponded with Wilbert afew months ago and helped a great deal to make the subject clearer. Tom also sent a number of corrections to some of my personalmisunderstandings so thanks to both of you along with Christopher andTom for all these very clear explanations. By the way Dylan, the IAS is growing and we need more authoritativevoices on Aroid l.. Thanks a bunch for making your firstcontributions, please don't make it your last! All of us need good info rather than much of the mishmash found on theinternet. I'm certain the IAS board will back me up in thanking you,Tom, Wilbert, Pete, Eduardo, David, Simon, Marcus, Marc, Julius and allthe authoritative voices that make sure we read good info! The nextissue of the IAS Newsletter will be out in about one month so if any ofyou on Aroid l haven't joined please take the time to do it now. www.Aroid.org By the way, I haven't read any responses to Ted Held's post regardinghearing some of Julius' personal stories. If you missed that post youcan find it here: http://www.hort.net/lists/aroid-l/feb10/msg00020.html I have already listened to his narration about Christmas dinner inTrinidad and strongly suggest all of you that have read Julius' greatposts but never had the pleasure of hearing his voice visit the site! It is a riot, and that does not count for the fact our old Aroid l friend is incredibly brilliant! Thanks again! Steve Lucas HTML +More www.ExoticRainforest.com Hannon wrote: Thanks to Wilbert for a very good synopsis of 'compact rootstocks' ortubers in Araceae. As a first time Aroid-Ler and longtime aroider Iwould like to offer a few comments.I think what Wilbert elaborates here makes perfect sense. My onlyquibble is that if we make no use of existing descriptive terminologythen we use more words than we need to to describe things, or we usewords that have imprecise or vague meanings. If all these structuresare rhizomes or (apparently) derived evolutionarily from rhizomes,that is very useful as a concept. Yet within this scheme there arestructures that can be differentiated, if arbitrarily, into morenarrowly defined notions such as tubers, rhizomes and corms.Some of us are weary of any confining definitions altogether. In thecase of rootstocks especially it is difficult to imagine any taxonomythat could capture and discretely name the different types found innature. In fact it has not been done. Still, it seems to me that acorm is something quite distinct, even if its origins are betrayed bypeculiar congeners, as in Wilbert's Amorphophallus example. Anymodular unit that may resemble a tuber or bulb and _replaces itselfeach growing season_ can rightfully be called a corm, regardless ofthe number of nodes/internodes involved or features of tunics vs.naked flesh. Annual replacement is the key trait of a corm.Other families exhibiting "true" corms that are replaced annually(sources in the botanical literature give inconsistent definitions)are the iris family (Gladiolus, Crocus, etc.), Themidaceae (Brodiaea,Milla, etc.) and some Cyanastraceae/Tecophilaeaceae. "Chains oftubers" can be found in Dierama and probably others and perhapssimilar ontogenic processes have been at work in these families. Asfar as I know the rootstocks of these plants have traditionally, inbotany, been labeled "corm" and not tuber or bulb. This concisedesignation continues to serve a useful purpose for the scientist andlayman alike. As Wilbert indicates, we have "traditionally" called thetuber-like structures in aroids, well, tubers.If we say there is only a morphological continuum, or that all therootstock types in a group are basically rhizomes, then clarificationand elucidation are sacrificed.Dylan Hannon --------------000501020207090908050008

From: <ju-bo at msn.com> on 2010.02.15 at 21:22:58(20601) Damn straight! Jules by Ted K HTML +More --_2cf86aa2-4202-4cc3-9880-e4ffcb052004_ _______________________________________________ Aroid-L mailing list Aroid-L@www.gizmoworks.com http://www.gizmoworks.com/mailman/listinfo/aroid-l --==============33937863649542219==--

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