308 



ESSENTIALS OF BOTANY 



processes, and conducting it to all parts of the plant body to 

 maintain growth in the tissues. Some of the plant food is 

 carried to the rudimentary flowers to form pollen and ovules 



together with the structures 

 which bear them. Another por- 

 tion of building material is later 

 carried to the cones of the year 

 before, to maintain growth in the 

 newly fertilized ovules.^ Still 

 another portion goes to the 

 two-year-old cones to complete 

 their growth. And it must be 

 remembered that each growing 

 and dividing cell is not a simple 

 sac, filled with formless proto- 

 plasm, but a very complicated 

 structure with many highly spe- 

 cialized parts. 



It requires considerable knowl- 

 edge of chemistry to follow even 

 the principal steps in the trans- 

 formations which food materials 

 undergo within the plant body. 

 Photosynthesis apparently often 

 results in sugar, which is quickly 

 changed into starch, then back 

 into sugar, for transference to 

 more remote parts of the plant. Here again it is trans- 

 formed (in root, stem, or fruit) into the starch or oil which 

 constitute the principal reserve material of most plants. 



1 Fertilization in the pine occurs about thirteen months after pollination. 

 See Bergen and Davis' Fr'mcipU^s of Botany, p. o74. 



2 This is really part root and part hypocotyl. 



Fii 



221. Effect of Cultivation 

 on Root 2 of Carrot. 



A, root of wild carrot, annual or 

 biennial ; B, root ol same spe- 

 cies cultivated, biennial. The 

 wild form can be changed in 

 four generations into the culti- 

 vated form. 



