International Aroid Society

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Hiyer!

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I=0Arecently had a discussion with few Aroid Oriented Individuals about proper=0Aterminology for the non-root, subterranean aroid parts. Or to put it another=0Away, do plants like Amorphophallus, Arum, Helicodiceros, Typhonium, Colocasia,=0AAmbrosina, and the like have tubers, corms or bulbs?

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The=0Aanswer is that they have tubers. (Or for dear Julius=E2=80=99 sake, =E2=80=9Cchubas=E2=80=9D). =0A

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A=0Abulb is composed of thick, modified leaves, arranged in layers, for food=0Astorage. An onion is a perfect example.

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A=0Acorm is composed entirely of stem tissue. It is literally just an underground=0Astem. It has an epidermal layer, a vascular cylinder with phloem and xylem and=0Acentral pith. A corm can also be a starch storage organ, but it still has true stem=0Atissue. This is why a corm has the new foliage growth coming from the top and=0Athe roots coming from the base. Corm examples are Crocus, Cyclamen and=0AGladiolus. A cormel is just a diminutive corm.

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A=0Atuber is just parenchyma (with some vascular tissue). It has an epidermal layer=0Awith some subdermal vascular tissue, and all the rest is parenchyma. It is=0Aalmost entirely a starch storage organ. This is why the foliage and the roots=0Aall come from the top. Most plants with tubers have them borne on stolons, but=0Athat is not necessary. In Amorphophallus, Arum and Typhonium for example, the=0Astem tissue is all encased in the small bud at the top of the tuber. That bud=0Agrows upward into a leaf or two, and outward into roots, with the tuber=0Abeneath. Other tuber examples are potatoes and Sinningia.

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A=0Abulbil, in the aroid sense, is just a tuber that forms on leaves or leaf axils.=0AIt is an unfortunate term as it obviously leads to confusion.

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I=0Areally hope that this is helpful to the Aroid community at large, and I hope it=0Acuts down on some of the confusion surrounding these terms. I am sure Pete,=0AWilbert, Tom, Julius, The Banta or someone can elucidate further, particularly=0Aas far as tuberous rhizomes or rhizomatic tubers are concerned.

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Happy=0Adays,

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Christopher

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D.=0AChristopher Rogers

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Senior=0AInvertebrate Ecologist/ Taxonomist

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