48 THE NATURE AND WORK OF PLANTS 



food from the fungus, and it therefore has no need of 

 true green leaves. It has lost these organs in times 

 past because of the very fact that it ceased to use 

 them. It is true of all living things, that as soon as 

 an organ ceases to be used or to be useful, it is devel- 

 oped less perfectly on each succeeding generation of 

 individuals until perhaps only a rudiment remains. 

 This is illustrated by the coral-root (Corallorhiza\ a 

 reddish orchid common throughout the Northern 

 states. This plant has not only reduced its leaves, 

 but on account of the activity of the fungus in 

 supplying it with food, the roots have been entirely 

 lost, the fungus of the mycorrhizas now living in 

 the short underground stems which have the appear- 

 ance of a bunch of coral. 



53. Roots as storage organs. During the sum- 

 mer season the plant manufactures much more food 

 than it can use at that time, and the surplus is 

 stored up until needed. The amount thus accumu- 

 lated is often sufficient to feed the plant through sev- 

 eral successive seasons in case it had no opportunity 

 to make its usual supply. Various parts of the body 

 are selected as places of storage. The beet is an 

 example of a root and a small portion of a stem be- 



