Re[2]: Tuber vs. Corm

     My 2 cents worth!!:
     
     I agree with Wilbert on the whole.
     
     No bulbs (storage in persistent leaf bases and/or scale leaves) in 
     Araceae known to me (Typhonodorum the nearest???).
     
     Most common morphological terms were invented for the depauperate 
     flora of Europe. Even the most fundamental terms such as stem, leaf 
     and root, let alone corm/tuber/rhizome, do not always work as clear 
     cut categories in tropical plants.
     
     Corm and tuber and rhizome intergrade in Araceae. I would think that 
     corm and tuber are at least sometimes interchangeable terms in say 
     Amorphophallus, and that tuber and rhizome are at least sometimes 
     interchangeable terms in say Colocasia. Alocasia produces corm-like 
     bulbils!!!
     
     This is no help at all!
     
     Rigorous definitions, when they are really needed, have to be 
     developed purposefully on a case by case (e.g. family by family or 
     genus by genus) basis (though that creates interesting problems if 
     structure needs to be codified in order to define the group). `Corm' 
     to an Iridaceae person is likely to be a different thing from corm to 
     an Araceae person. This doesn't necessarily matter.
     
     Pronunciation is a free-for-all, but make it BEAUTIFUL to other 
     people. Most plant names are worth savouring - even Amorphophallus!
     
     Alistair Hay
     
     
     
     


______________________________ Reply Separator _________________________________
Subject: Re: Tuber vs. Corm 
Author:  <aroid-l@mobot.org> at mailgate
Date:    12/1/99 19:45


At 06:58 PM 1/11/99 -0600, you wrote:
>I was talking with a Ph.D Botanist (name withheld for obvious reasons) who 
>is a recognized authority on different types of bulbs....  He said, when I 
>asked him, that Amorphophallus is a corm and not a tuber or bulb.  I think 
>he said something about the cell structure.....
>
>Do we want to start this discussion again....??? 
>
>Which is it?
>Dewey
>
>Dewey E. Fisk, Plant Nut
>THE PHILODENDRON PHREAQUE
>Your Source for Tropical Araceae
>
>
Dewey:
     
   I don't know what definition your botanist was using, but I define a
corm as a compressed, usually subterranean, modified stem that is 
surrounded by dry, scale-like leaves.   A tuber is a thickened, compressed, 
more or less fleshy, usually underground stem.  Using these definitions, 
the modified underground stems of the species of Amorphophallus are tubers.
 I have not seen any evidence of the modified stems being surrounded by
dry, scale-like leaves. The problem is that some of the tubers have a 
corm-like shape with a large apical bud.  From what I have seen of the 
genus, the underground stems are quite varied.  Some look very much like a 
rhizome, some look like the "typical" tuber, and others look like corm.  We 
are looking at a continuum here, and definitions, at least simple ones that 
you learn in school, usually only cover the usual, most common conditions. 
The thing that I think is important is looking at the range of 
modifications, then I think that it is obvious that they are tubers.  That 
is this Ph.D.'s two-cents worth. 
     
Paul M. Resslar
Professor of Biology
Virginia Wesleyan College
1584 Wesleyan Drive
Norfolk, Virginia 23502-5599
U.S.A.
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