32 FODDER AND PASTURE PLANTS. 



reaching a height of from twenty to twenty-five feet. In some the 

 ears are only an inch or two long; in others as much as sixteen inches. 

 The number of kernel rows, which is always even, ranges from eight 

 to twenty-four or more, according to variety. Abnormal individual 

 ears sometimes have as few as four in some varieties, or as many 

 as forty-eight in the large-eared sorts. The size of the kernels, their 

 shape, colour, chemical composition, etc., are extremely variable. 

 According to Dr. E. L. Sturtevant, the varieties may be classified 

 into the following seven principal groups. 



1. The pod corns have each kernel enclosed in a pod or small 

 husk and the ear thus formed is also enclosed in husks. All other 

 groups have naked kernels within the husks. It is doubtful, however, 

 whether the pod corns form a natural group. Possibly the husks 

 surrounding the kernels are abnormal and might be found in any of 

 the main groups. This opinion is supported by the fact that the 

 kernel structure varies in the pod corns. 



2. The pop corns are characterized by an excessive proportion 

 of the corneous endosperm; that is, the nutritious matter, which 

 forms the greater part of the kernel and is stored for the use of the 

 sprouting germ, contains little starch. In this group the kernels and 

 ears are small. The property of popping over a fire, which is the 

 complete turning inside out of the kernel through the explosion of 

 its moisture content, is most pronounced in varieties which have a 

 corneous endosperm throughout and is less marked as the percentage 

 of starch increases. 



3. The flint corns may be recognized by the central part of 

 the endosperm being starchy and completely surrounded by a corn- 

 eous coat, varying in thickness in different varieties. Cartier found 

 varieties of this group in the neighbourhood of Montreal. 



4. The dent corns have the central starchy part of the endo- 

 sperm surrounded by a corneous layer at the sides of the kernel only, 

 the starchy endosperm thus extending to the summit of the kernel. 

 When the endosperm dries and shrinks, various indentations are 

 formed on the summit of the kernel. The dent corns are extensively 

 grown in the United States, the number of varieties exceeding that 

 of all other varieties combined. 



5. The soft corns have no corneous endosperm. The shrinkage 

 in ripening is therefore uniform in all parts of the kernel. To this 

 group belong the mummy corns of Peru and Chili. 



