CHAPTER III. 



CLASSIFICATION AND BOTANICAL CHAR- 

 ACTERISTICS 



CLASSIFICATION 



The Polymorphic species (Zea mays) is divided into six distinct 

 sub-groups by Dr. E. L. Sturtevant* His classification is based upon 

 an extended examination of almost 800 varieties. This grouping is 

 founded on the internal structure of the kernels of the cultivated 

 varieties and the presence of a husk on each kernel in the so-called 

 aboriginal form. 



The following species-groups are established : 



I. ZEA TUNICATA— The Pod Corn. This is also known as 

 primitive corn. In this group each kernel is enclosed in a pod or husk, 

 and the ear thus formed is also enclosed in husks. The seed is sup- 

 plied by our seedsmen for growing as a curiosity. Instances are on 

 record where seemingly the dent corn has reverted to this type. The 

 kernel itself is rather hard and flinty. 



II. ZEA EVERTA.— The Pop Corns. This species-group is 

 characterized by the excessive proportion of the corneous endosperm 

 and the small size of the germs, kernels and ears. The best varieties 

 have a corneous endosperm throughout. This gives the property of 

 popping, which is the complete eversion or turning inside out of the 

 kernel, through the explosion of the contained moisture on the appli- 

 cation of heat. This type is very hardy and the embryo has wonder- 

 ful germinative vitality. Its culture is an important industry in cer- 

 tain districts near the larger cities. 



III. ZEA INDURATA— The Flint Corns. A species-group 

 readily recognized by the occurrence of a starchy endosperm enclosed 

 in a corneous endosperm, as shown in a split seed. This corneous 

 endosperm varies' in thickness with varieties. It is grown farther 

 north than any of the other types. The kernel is therefore usually 



•Bulletin No. 67 of the U. S. Department of Agricnlture. 



