Re: [] Tubers, corms and bulbs, oh my!

**K* M* <k*@spatulacity.com>**

Thanks, Christopher. I always called them tubers but thought that they 
were more correctly called corms. I thought that because a botanist 
friend of mine said they were corms.
-Ken Mosher

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
>
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