STRUCTURE OP ..lAIZE I43 



lower leaves die off before maturity, activity at any one time is 

 confined to about twelve. The width of the blade varied from 

 three and three-quarters to five and one-eighth inches. At the 

 Missouri Station the total external leaf surface on twelve living 

 leaves of a single maize plant was found to be twenty-four 

 square feet.^ As 12,000 plants per acre are not an unusual 

 stand, the leaf surface may be more than a quarter of a million 

 square feet on an acre, or about six times the area on which the 

 plant stands. 



At the Michigan Station the leaves constituted somewhat 

 more than a third of the dry matter when the grains were in 

 milk, and a little m.ore than a fifth when the plant was ripe. 

 During this period the percentage of dry matter of culm re- 

 mained about the same, the decrease in percentage of dry 

 matter in leaves having been offset by a corresponding increase 

 in the ears.^ 



The outer edges of the leaf blade grow faster than the por- 

 tion next the midrib, giving a wa\y effect to the blade and 

 giving it an elasticity which aids it to withstand wind. In the 

 upper portion of the blade, on either side of the midrib, are to be 

 found large wedge-shaped (bulbifonn) cells which on filling with 

 water cause the young leaf to unfold and which during drouth 

 cause the leaf to roll, thus reducing the evaporation from the 

 plant The under surface of the leaf is further protected, also* 

 against transpiration by a strong cuticle. The ligule tightly 

 clasps the stalk, preventing the entrance of water and accom- 

 panying dirt between sheath and culm: it also prevents the 

 sheath from rotating upon the culm as in most of the grasses. 



213. Relationship of Grain to Stover. — Of two stalks bearing 

 the same quantity of grain, the smaller is to be preferred, where 

 grain is the principal object sought. The larger the stalks the 

 more food material necessary to produce them, the more ground 



I Mo. Bui. 5 (1SS9). 



« Mich. BuL 154 (i89S),p. 272. 



