l6o BOTANY OF CROP PLANTS 



Stem. — Corn is the largest of the common cereals. How- 

 ever, no other cereal varies so in size. There are dwarf forms 

 scarcely 3 feet high, while some are 15 or more feet high. 

 The stem is jointed as in all grasses. The internodes, how- 

 ever, are not hollow, but are filled with a soft pith through 

 which run numerous vascular bundles, the libers. The 

 nodes are solid as in other grasses. The internodes are 

 furrowed on the side next the leaf blade. The corn plant 

 produces ''suckers" which correspond to the "stools" of 

 wheat, as to their morphology. "Suckers" are secondary 

 stems or branches arising from the lower nodes. These 

 branches develop their own roots. "Suckers" of corn are 

 undesirable, for they do not, as a rule, produce ears, although 

 they are heavy soil "feeders." 



Leaves. — The leaves are arranged alternately on opposite 

 sides of the stem as in all grasses. They vary in number from 

 8 to 20. The blade is long and flat; the ligule closely invests 

 the stalk, acting as a rain-guard. Water that runs down the 

 stem and leaf blade is prevented from entering the space 

 between the culm and leaf sheath by this tightly fitting 

 hgule. 



The corn leaf is thrown into a number of folds along the 

 edges and at the base. This is due to the more rapid growth 

 of the cells at these points. The corn plant is moderately 

 well adapted to dry conditions. An examination of the 

 leaf structure explains this. On the upper surface of the 

 leaf blade, along either side of the midrib, are a number of 

 large wedge-shaped cells; these absorb water readily in moist 

 weather, become turgid, and thus flatten the leaf out. In 

 dry weather, these cells lose their turgor. Hence the leaf 

 rolls up, presenting a smaller evaporating surface. In addi- 

 tion to this adaptation to dry conditions, the cuticle of the 

 lower surface of the leaf is much thickened, and the water 



