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. 
