Ii6 PLANT-BREEDING 



pression is caused by the shrinkage of the starchy matter 

 in drying. The dent varieties are almost the exclusive corn 

 crop of the corn states and are of supreme value in the feed- 

 ing of cattle; they are more numerous than all the varieties 

 of the five remaining groups taken together. 



The soft corns, Zea Mays amylacea, have no corneous 

 endosperm, as their name indicates. The kernels, however, 

 shrink uniformly and do not become wrinkled in drying. 

 This group includes some of the oldest varieties, as, for in- 

 stance, the mummy corns of Peru and Chile, and the very 

 largest-kerneled type, the Cusco. 



The sweet corns, or Zea Mays saccharata, are character- 

 ized by their wrinkled and more or less translucent seed. 

 This condition, however, is not caused by the horny part of 

 the kernel, but by the starchy tissue in wliich the starch is 

 almost wholly absent. It is replaced by a sweet constituent 

 or kind of sugar, belonging to the group of the dextrines. 

 It is mainly grown for table use and for canning purposes, 

 the grain being canned before becoming ripe. Maine and 

 New York are the principal states for this culture, which, 

 however, extends all along the Atlantic coast. 



In each of these six main groups there are a number of 

 varieties which are partly distinguished by the forms of the 

 kernels, whether broad or deep, partly by the proportion of 

 the horny and the starchy part of the endosperm, and partly 

 by many other subordinate marks. E. L. Sturtevant, in 

 his Varieties of Corn (U. S. Dept. of Agriculture, 1899, N. 

 57) enumerates 300 varieties of dent corn, 70 of flint, 60 of 

 sweet corn, and so on. These varieties or sub-races are 

 cultivated under different names, and their characters are 

 said to be constant and more or less sharply defined, not 

 changing under the influence of soil, climate, or treatment. 

 Among the dent corns the dimple-dented, crease-dented, 

 pinch-dented, and ligulate-dented may be cited as instances. 



