84 SOUTHERN FIELD CROPS 



provided mth an arrangement by which, in dry weather, 

 the size of the opening is reduced, thus decreasing the 

 amount of water thrown off by the leaf. 



The corn leaf has also another means of economizing in the 

 transpiration of moisture. This is seen in the rolling together of 

 leaves in the middle of a hot dry day. This curling, or rolling, 

 of the leaves is due to the presence of special cells, which, on 

 parting with a portion of their moisture in dry weather, cause the 

 leaf to fold inward. 



In the South, the corn plant is especially liable to lose pre- 

 maturely the use of its leaves through their drying, or "firing." 

 This may be due to dry weather, to inadequate preparation of the 

 soU, to lack of proper cultivation, to root pruning, or to other 

 causes. 



The leaf consists of two principal parts : the sheath, or that 

 part which is clasped around a portion of the stem, and the blade, 



Fig. 33. — Part of a Corn Leaf, showing Wavy Margins. 



or free part of the leaf. The outer margin of the blade is wavy 

 or scalloped (Fig. 33). This permits the leaf to turn from the 

 wind like a windmill thrown out of gear, and thus to avoid 

 throwing too great a strain on the stem. 



84. Ear-branch and shucks. — The shank on which the 

 ear is borne represents a branch. That this is a branch is 

 apparent (1) from its position in the angle between the 

 stem and the leaf -sheath ; (2) by the fact that the shank 

 has nodes similar to those of the main stem ; and (3) by 



