ORGANS OF NUTRITION. 



115 



b. The Tuber. ( Fig<i. 219 and 220.)— This is a subterranean 

 branch, arrested in its growth, and excessively enlarged by the 

 deposition of starch and other nutritious substances in its tissue. 

 It has upon its surface a number of little buds, or eyes as they 

 are commonly called, from which new plants are formed the 

 Fig. 219. 



Fig. 219. Tubers of the common Potato (.Solanum tuberosum). 



succeeding year. The possession of these buds indicates its 

 nature as a "^ kind of stem. The Potato (fig. 219) and Jeru- 

 Fig. 220. Fig. 221. 



Fig. 220. Tubers of the Jerusalem Artichoke {Ilelianthus tuberosus). 



Fig. 221. A monstrous branch or bud of the common Potato. From The 

 Gardcner^s Chronicle. 



salem Artichoke {fig. 220) are good illustrations. A case 

 was reported in the " Gardener's Chronicle " of a Potato 

 plant in which the buds in the axils of the true leaves above 

 ground showed a tendency to form tubers {fig. 221), by which 

 I2 



