180 CORM. TUBER. [BOOK i. 



The Corm, fig. 25, (Lecus of Du Petit Thouars, Plateau 

 of De Candolle), is the dilated base of the stem of Monocoty- 

 ledonous plants, intervening between the roots and the first 

 buds ; and forming the reproductive portion of the stem of 

 such plants when they are not caulescent. It is composed of 

 cellular tissue, traversed by bundles of vessels and pleuren- 

 chym, and has often the form of a flattened disc. The fleshy 

 " root " of the Arum, that of the Crocus and the Colchicum, 

 are all different forms of the corm. It has been called bul- 

 botuber by Ker, and bnlbus solidus by many others ; the last 

 is a contradiction in terms. (See Bulb.) 



Usually the bud of the corm is at its point : in the Col- 

 chicum, however, it is on one side near the base. 



The stems of Palms have by some writers been considered 

 as an extended corm, and not a true stem, but this is an 

 extravagant application of the term ; or rather an application 

 which reduces the signification of the term to nothing. A 

 corm is a depressed subterranean stem of a particular kind ; 

 the trunk of a Palm is, as far as its external character is con- 

 cerned, as much a stem as that of an Oak. De Candolle 

 applies the name corm only to the stems of Cryptogamous 

 plants, and refers to it the Anabices of Necker. 



The Tuber, fig. 26., is a solid thickened subterranean stem, 

 provided at the sides with latent buds, from which new plants 

 are produced the succeeding year, as in the Potato and 

 Arrow-root. A tuber is, in reality, a part of a subterranean 

 stem, excessively enlarged by the development to an unusual 

 degree of cellular tissue. The usual consequences attendant 

 upon such a state take place ; the regular and symmetrical 

 arrangement of the buds is disturbed ; the buds themselves 

 are sunk beneath the surface, or half obliterated, and the 

 whole becomes a shapeless mass. Such is not, however, 

 always the case ; the enlargement sometimes occurs without 

 being accompanied by much distortion, and the true nature 

 of the tuber stands revealed ; this is remarkably the case in 

 the Asparagus Potato. In most, perhaps all tubers, a great 

 quantity of starch is deposited, on which account they are 

 frequently employed as useful articles of food. 



The Creeping stem, fig. 27. (soboles), is a slender stem, which 



