46 CORN 



Just inside and springing from the ligule is a short, thin, yet rigid 

 prolongation or fringe which clasps the internode of the stem very 

 closely. This is the rainguard, which, contrary to common opinion, 

 instead of catching the rainfall and collecting it inside the leaf sheath, 

 transfers it to the opposite side of the stalk and allows it to drip on 

 the rainguard and ligule below. This rainguard in turn does the same 

 thing. The water is carried in a zigzag manner until it reaches the 

 ground. The fact that, after a light shower in August, a wet spot is 

 noted at the base of each hill of corn can be accounted for because of 

 this process. 



The midrib and the veins, which are only larger gatherings of 

 fibro-vascular bundles, serve to hold the green surface spread out to 

 the sunlight. They are also circulatory ducts. The epidermis of the 

 leaf is not very thick or tough. This is shown by the tendency of 

 the point of the blade to split in a heavy, whipping wind. The green, 

 cellular structure between the veins of the leaf of corn is, in the plant's 

 early growth, very turgid and of a dark color. The curious openings 

 on the surfaces of the leaf, known as stomata, are very active in the 

 corn plant. Guarding each opening will be found two crescent-shaped 

 cells known as guard cells. The stomata act as passage ways for the 

 transpiration of moisture and for the inlet and outlet of. carbon dioxide 

 and oxygen. They cannot properly be spoken of simply as breathing 

 pores. 



FIGURING THE LEAF SURFACE OF A CORN STALK. As 

 the corn plant requires over 500 tons of water for the formation of one 

 ton of dry matter, the leaf surface must necessarily be large to accom- 

 modate this enormous transpiration. In figuring the surface area of 

 a leaf, measure the width three inches from the ligule, also at a point 

 six inches from the tip of the leaf. Add these two widths, divide by 

 two to get the average. Multiply this average width by the length of 

 the leaf from the ligule to that point, six inches from the tip. To the 

 area of this rectangle, add the area of the isosceles triangle at the tip 

 of the leaf, which is six inches in altitude and as wide as the leaf is 

 at that point. The sum of the two areas gives the leaf surface on one 

 side of a single leaf. Multiply this sum by two and the entire surface 

 of leaf will be ascertained. For approximate calculations, the surface 

 area of one leaf multiplied by the number of leaves on the stem will 

 give the entire leaf surface of the stalk. 



An Example. Leaf 36 inches in total length, 



4 inches wide at lower measurement (3 



inches from ligule), 

 3 inches wide at upper measurement (6 



inches from tip of blade), 

 y/2 inches average width. 

 Three and one-half inches multiplied by 30 inches (36-6 inches) 

 equals 105 square inches, area of rectangle. 



