Jim, On searching various botanical dictionaries and looking at the literature pertaining to a wide range of geophytic plants, it is clear that there is little consensus on what exactly a corm is. Different contemporary scientists use different terms for the same structure in the same plants (see Araceae), so if they do not agree there may be little hope for us. The definition that seems most exclusive and precise to me includes the essential fact that the organ *replaces itself* each season: this would include many irids (Freesia, Gladiolus, etc.), Tecophilaeaceae, many "tuberous aroids", Gloriosa and even a few begonias as well. It gets interesting when we see things like Dierama or Ferraria or even some Amorphophallus species with "chains" of corms that persist for several seasons. Are they still considered corms if they are persistent in this way? I read somewhere that indeed tulip bulbs (Calochortus, too, I think) are different in that the bulb is derived from modified cataphylls or prophylls rather than leaf bases, but I did not realize they replace themselves. Since the stem tissue portion of a 'normal' bulb is not replaced each season it would not qualify as a corm, even though some definitions of corm simply say that it is stem tissue. Annual replacement is the key distinguishing trait I think, even if it is not absolute in all cases. This is a great topic but unfortunately there is a paucity of authoritative work on defining and categorizing these structures. There is a lot of work to be done in this area-- morphology is not passe! Some are truly anomalous, as the rootstocks of some Dioscorea species, which have confusing features of both stem and root tissue at the anatomical level. The word "rootstock" is indispensable. Dylan