80 



STRUCTUHAL BOTANY. 



beneath the surface-soil, after the leaves and annual stems have 

 perished. 



237. THE TUBER is an annual thickened portion of a subterra- 

 nean stem or branch, provided with latent buds called eyes, 

 from which new plants ensue the succeeding year. It is the fact 

 of its origin with the ascending axis, and the production of buds, 

 that places the tuber among stems instead of roots. The Po- 

 tato and Artichoke are examples. 



238. The stem of the Potato-plant sends out roots from its base, and branches above, 

 like other plants; but we observe that its branches have two distinct modes of develop- 

 ment. Those branches which rise into the air, whether issuing from the aboveground 

 or the underground portion of the stem, expand regularly into leaves, etc. ; while those 

 lower branches which continue to grope in the dark, damp ground, cease at length to 

 elongate, swell up at the ends into tubers with developed buds and abundance of nutri- 

 tious matter in reserve for renewed growth the following year. 



Tnhr,x <(.- Hi ft/ f/ioit-. 260, The common Potato (Solatium). 261, Artichoke (Helianthus). 262. Sweei 

 Potato (Convolvulus). 



239. THE CORM is an underground, solid, fleshy stem, with 

 condensed internodes, never extending, but remaining of a 

 rounded form covered with thin scales. It is distinguished from 

 roots by its leaf-bud, which is either borne at the summit, as in 

 the Crocus, or at the side, as in the Colchicum and Putty-root 

 (Aplectrum). 



