THE STARCHES. 



STARCHES OF GRAMINACE/E. 



Class, Monocotyledones. Order, Graminales. Family, Graminacese. Genera repre- 

 sented: Zea, Andropogon, Panicum, Oryza, Triticum, Secale, Hordeum, Avena, 

 Arrlienatherum . 



The Graminacese ninkc up an enormous family, including about 300 genera and 3,000 species, 

 and comprises not only the various grasses which serve as the main or sole food of graminivorous 

 animals, but also the cereals which constitute, directly or indirectly, the most important single class 

 of plant foodstuffs consumed by man. Representatives of nine of these genera were studied. 



GENUS ZEA. 



The genus Zea, as now limited, is founded on the single polymorphous cultivated species Z. 

 mays, whose place of origin is probably Mexico and whose parentage is still a matter of specula- 

 tion. According to some authors, it is a true species of an unkno^vn wild prototype; others regard 

 it as an offshoot of Euchlwna mexicana Schrad. (teosinte) ; and others as a hybrid of E. mexicana 

 with some unknown species or variety. The varieties or horticultural forms are quite numerous; 

 they have been classified by Sturtevant (U. S. Dept. Agriculture, Office Experiment Stations 

 Bulletin 57, 1899) into seven "species groups" in accordance with peculiarities of the ears and ker- 

 nels: (1) Z. tunicala, the pod corns; (2) Z. everta, the pop corns; (3) Z. indurata, the ffint corns; 

 (4) Z. indentata, the dent corns; (5) Z. amylacca, the soft corns; (6) Z. sacchnrata, the sweet corns; 

 and (7) Z. a?iiyka-saccharala, the starchy sweet corns, of which latter very little is known. 



According to Sturtevant's data, in the species group Zea rnay.s var. tunicata (Z. mays tunicala 

 Sturtevant) "each kernel is inclcsed in a pod or husks, and the ear thus formed is inclosed in husks." 

 The species group Z. mays var. everta "is characterized by an excessive proportion of the corneous 

 endosperm and the small size of the kernels and ear. The best varieties have a corneous endo- 

 sperm 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 application of heat. 

 A small deposit of starchy endosperm does not greatly interfere with this property of popping, but 

 when the starch endosperm is in excess, as in flint corn, the kernel does not evert, but the corneous 

 portion only explodes or splits, leaving the starchy portion unchanged." Z. mays var. indurata 

 is recognized by "the occurrence of a starchy endosperm inclosed in a corneous endosperm, as 

 shown in the split seed. The corneous endosperm varies in thickness with varieties. When very 

 thin at the summit of the kernel the shrinkage of the starchy endosperm may cause a depression, 

 thus simulating externally a dent from which its structure at once differentiates it." The group 

 Z. mays var. indentata is "recognized by the presence of corneous endosperm at the sides of the 

 kernel, the starchy endosperm extending to the summit. By drying and shrinkage of the starch 

 matter the summit of the kernel is drawn in or together, and indented in various forms. In different 

 varieties the corneous endosperm varies in height and thickness, thus determining the character of 

 the indented surface." The group Z. mays var. amylacea "is recognized by the absence of corneous 

 endosperm. Through the uniformity of the shrinkage in ripening there is usually no indentation, 

 yet in some varieties an indentation may more or less frequently disappear, but splitting the kernel 

 invariably determines the class." Z. mays var. saccharata "is characterized by the translucent, 

 horny appearance of the kernels and their more or less crinkled, -rtTinkled or shriveled condition." 

 24 343 



