PLANT FOOD AND GROWTH. 29 



vanced. In the later stages of growth comparative- 

 ly little is received from the soil, but so long as the 

 plant remains green it continues to absorb carbon 

 from the air and to produce starch, sugar, and other 

 compounds. The dry matter in the corn plant may 

 more than double in weight after it has reached its 

 full height. 



Much of the material stored up in the matured 

 seed has been taken from the roota, stalks and leaves, 

 in the case of annual as well as biennial plants. There 

 is valuable food for animals in the stalks and leaves 

 of fully matured plants — notably in the grasses and 

 clovers — but much less than before the seeds have ma- 

 tured. The food is not lost, but transferred from 

 other parts of the plant to the seed. The production 

 of seed is the chief purpose of many plants, not only 

 that they may perpetuate their kind but that they 

 may be most useful to man. 



