COBN STBUCTUBE 83 



The stem consists of internodes of variable length, separated 

 by solid partitions at the nodes or joints. The internodes on 

 certain parts of the plant are grooved, which seems to be a pro- 

 vision for accommodating the shank, or ear branch. When shoots 

 or ears arise, they spring from a bud at the base of this groove. 

 This bud is completely enwrapped by the leaf-sheath, which 

 serves to protect it. 



Under some conditions, partly dependent on variety, character 

 of season, and distance between plants, "suckers" or basal 

 branches spring from the buds on the main stem near the crown. 

 These suckers afterwards develop independent root systems. 

 Removal of such suckers is an important cultural operation in the 

 South, since they take up water and plant-food needed by the 

 parent plant. Their removal from Northern corn-fields is less im- 

 portant, for there several plants may be safely grown in each hill. 



The tendency of individual corn plants to sucker is hereditary ; 

 thus Hartley found that when both the male and female parents 

 produced suckers, 14| per cent of the offspring developed 

 suckers ; while only 2J per cent of the plants bore suckers in the 

 case of those stalks neither of whose parents had produced suckers. 

 Therefore, in selecting corn plants for seed, preference should be 

 given in the South to those free from suckers. 



83. Leaves. — The corn plant is supplied with a con- 

 siderable number of long, broad, tapering leaves. The 

 number is most frequently twelve to eighteen ; and a leafy 

 plant is probably desirable. The main uses or functions of 

 leaves are (1) to take up from the air its carbon dioxid 

 for use in building up the tissues of the plant, and (2) to 

 throw off the surplus water into the air, thus helping to 

 lift other supplies of soil moisture to the leaves with the 

 contained plant-food. For these two purposes, the leaf 

 is provided with immense niunbers of minute openings or 

 pores (stomata). These stomata are especially numer- 

 ous on the under sides of leaves ; each pore or stomate is 



