PHYSIOLOGY OF THE CORN PLANT 



167 



able conditions these lateral roots develop abundantly 

 and rapidly and the root-system of corn is thus profusely 

 branched. 



210. Growth of stems (Fig. 25). — All of the nodes in 

 the stem of a corn plant are formed while the plant is quite 

 young. The subse- 

 quent growth or 

 elongation of the 

 stem is due to the 

 extension of the in- 

 ternodes. Above 

 each node there is a 

 layer of cells pos- 

 sessing a dark green 

 color and filled with 

 sap. These cells to- 

 gether with the ex- 

 treme tip of the 

 stem constitute the 

 growing points of 

 the corn stalk. As 

 the average corn 

 stem possesses from 

 fifteen to twenty 

 nodes and conse- 

 quently as many growing points, it is enabled., to 

 lengthen very rapidly during the growing season. The 

 elongation of the corn stem has been likened to the un- 

 folding of a telescope. The corn stem increases in diameter 

 as a result of the internal accession of cells, rather than by 

 adding layers on the outside. It is therefore an endogenous 

 stem. 



211. Growth of leaves. — The author has been able 



Fig. 25. — Illustrating development of corn 

 stem: 1, plant about 10 inches high; 2, sec- 

 tion of 1, at base, showing that all nodes, 

 leaves, and tassel are more or less developed 

 at this stage; growth is internodal; 3, full- 

 grown, stem with leaves removed; 4, cross- 

 section of stem. 



