From: "Julius Boos" ju-bo at email.msn.com> on 2000.07.30 at 15:31:01(5177)
Dear Christophe,
Let me TRY to assist you with this technical one, since this is your second
plea to this list---I had hoped one of the 'big guns' out there would have
tackled this one, but here goes--
!) Both are closely related to each other. The most important difference
between the two is microscopic, and found within the female flowers. In
Colocasia the placentae are parietal (along the interior sides of the
gynoecium, which is the embrionic future berry) from top to bottom, and the
many funicules ('stems'?) of the ovaries attach to the placentae along the
interior sides of the ovary.
In Alocasia the placenta is basal, and the sparser number of
funicules/ovaries are attached to this placenta within the gynoecium, but
along its interior base.
2) Colocasia IN GENERAL has a partially peltate leaf blade, while GENERALLY
Alocasia has any shaped leaf blade you want to imagine, from entirely
peltate to sagittate, to deeply pinnatifid!!!. GENERALLY Colocasia has a
small sterile region at the tip of the spadix, while GENERALLY Alocasia has
a longer sterile region at the apex of the spadix.
If you have a plant you are doubtful about, the best way to get an I.D. is
to post a picture of the plant, many will jump at the chance to I.D. it, or
at least give a good guess!
I again urge anyone who is seriously interested in Aroids to buy the book
'The Genera of Araceae' by S.J. Mayo, J. Bogner and P. Boyce, there you will
find MOST of the answers to any questions you may have about this wonderful
family of plants we SO love! It is available from the IAS on this list,
just post a request for information, it costs about U.S. $135.00.
Good growing,
Julius
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