Re: Tuber vs. Corm
>This question was discussed at some length last fall on a gesneriad growers
>listserve - one member found the following definitions on the web:
>On the GardenWeb site (http://www.gardenweb.com/glossary/):
>Corm: The enlarged fleshy base of a stem, bulb-like but solid.
>Tuber: A thickened and short subterranean branch having numerous
>buds or eyes and used for food storage.
>>From the glossary of the Flora of Australia
>Corm: A fleshy, swollen stem base, usually underground, in which
>food reserves are stored between growing seasons.
>Tuber: A storage organ formed by swelling of an underground stem
>or the distal end of a root
>>From the University of Illinois extension service
>Corm: Swollen underground stem tissue. The basal plate is
>located on the bottom of the corm; roots develop from this plate.
>Tuber: Short, fat underground stem tissue with growing points,
>buds or "eyes" as in a potato. Tubers can be flat, rounded or
>irregular in shape. (Sinningia is used as an example of a
>So, from these definitions, it would seem that a corm is ALWAYS
>the swollen BASE of a stem. There is a basal plate on the bottom
>of a corm from which the roots arise. A bulb is the swelling of
>an underground stem (not necessarily the base of an above-ground
>stem), and has multiple growing points.
>An additional point that was made, after it was suggested that tubers and
>corms may be the same thing (essentially), but having developed from two
>different evolutionary lines, was that to the best of the writer's
>knowledge, no monocot families had tubers.
>While not an expert, my inclination after some thought is to agree until
>exceptions can be raised. An interesting side point for someone to
>explore. Monocots seem to have either bulbs or corms as their underground
>storage units -- dicots have tubers.
>Another note, especially significant for aroid growers - corms do not
>necessarily have the basal plate located at the bottom--more often than not
>with the corm-growth aroids, the roots are coming out above the storage
>tissue, not from below.
>Another point, along a different path -- on the subject of bulbils as the
>corm offshoots produced at the base or along the stem at leaf axils on some
>aroids. My sense is that this is a non-scientific classification, which
>means any term goes. The structures are kind of bulb-like (but not
>really), therefore, bulbils. Arguing terms of this sort could go on and on
>and, well, you get the point. Kind of like ginger root, meaning, of
>course, the stem, or even more abstractly, bromeliad "pups," the basal
>sidebranch growths that arise along with or immediately following flowering
>with most bromeliads most of the time. Are these really pups? And on it
>Above all, good growing.