DESCRIPTION OF THE COBN PLANT 31 



18. The stem. — The stem of maize differs from that of 

 other cereals in the fact that it is solid — filled with pith — ■ 

 while others are hollow. The maize stem may vary in 

 height from 2 feet, in the case of dwarf pop corn, to 18 or 

 20 feet in some of the tall southern varieties. 



The nodes not only serve to strengthen the stem, but 

 are also the points of origin for all its lateral outgrowths, 

 as roots, branches (tillers), leaves, and ears. 



The stem usually extends not more than three to five 

 inches below the ground surface. This part is divided 

 into about six to ten short nodes, each bearing a whorl 

 of roots. Above the soil surface each node bears a leaf 

 and in addition either a branch or an embryonic ear. The 

 early northern varieties of maize, with a height of about 

 6 feet, usually have about eight to ten nodes above the 

 soil, while the tall southern varieties may have eighteen 

 to twenty. A typical plant in Illinois or Indiana will 

 have about fourteen nodes, with one or two branches from 

 the surface nodes and an embryonic ear at each node; 

 usually, however, only the ear at about the eighth node 

 develops, the others remaining dormant. 



In Fig. 13 is shown a stem from a plant about 10 inches 

 high. The full nimiber of nodes, and also of leaves, is 

 formed. Growth of the stem from this point on will be by 

 a lengthening of the inter nodes, but there will be no in- 

 crease in number of nodes. This is called internodal 

 growth, in distinction from the apical, or terminal, growth 

 of many other plants — as peas and beans, where new 

 growth is constantly taking place at the apex. 



The outer part of the stem is a thin shell of hard tissue, 



activity of the cell. The result is a, much greater movement into the 

 root-hair than exudation out of if. The soil solution passes from the 

 root-hair into the root and is finally transmitted to the stem and leaves. 



