4S8 



SOLANACE^ 



ground and the thin parts of the underground stems die ; the 

 tubers remain dormant below during winter, and in the following 

 spring germinate and send forth new shoots from their ' eyes.' 



The tubers from a one-year-old plant are small, often not 

 larger than a broad bean, and it is only after three or four years 

 growth that they reach the size of ordinary potatoes. 



Fig. 140. 

 Potato seedling (26 days' old), later stage 

 of Fig. 139. The Plumule e has developed 

 considerably, and in the axils of the coty- 

 ledons two shoots d have been produced. 

 a- hypocotyl ; ^ root ; c cotyledons ; c 

 epicotyl ; jr ground-line (Natural size). 



Fig. 141. 



Potato seedling (10 weeks' old), later 

 stage of Fig. 140, The shoots d have 

 now pushed their way below ground and 

 at their tips small tubers have formed. 

 (Natural size.) 



Root. — The roots of the potato plant extend themselves 

 chiefly in the upper layers of the soil, and are fibrous and 

 copiously branched. The primary root and its branches are 

 distinct from the tuber-bearing rhizomes (Fig. 141), but from the 

 nodes of all the stems below ground adventitious roots arise in 



