CH. II] 



POTATO. 



23 



to the cotyledons ; they are not only of different shape and 

 consistence, but are differently arranged on the stem. 



Potato (Solanum tuberosum). 



The accumulation of reserve material is by no means 

 confined to seeds, and it is especially well seen in those 

 underground parts of plants which are known as bulbs 

 and tubers. The potato is a good example of the tuber, 

 and the fact that it contains a store of food intended for 

 the future use of the plant, but diverted for his own use 

 by man (and by the potato-disease fungus) is sufficiently 

 familiar. 



FIG. 6. 



HORIZONTAL UNDERGROUND STEM, or rhizome of a sedge, sending adven 

 titious roots downwards and leaves upwards. 



From Le Maout and Decaisne. 



