364 



STARCHES OF GRAMINACEiE. 



Curve of Reaction-Intensities of Starch of Oryza sativa 

 var. 



a light blue. After boiling for 2 minutes the solution colors a deep indigo-blue, but the gelatinized 

 grain-residues do not color at all. The capsules assume an old-rose tint when an excess of iodine 

 is added. 



Staining Reactions. — With gentia7i violet the grains begin to stain at once and in 30 minutes 

 they are rather lightly stained. 



With safranin the grains begin to stain at once and 

 in 30 minutes they are rather lightly stained. 



Temperature Reaction. — The temperature of gelati- 

 nization is 74° to 75.5° C, mean 74.75°. 



Effects of Various Reagents. — ^With chloral hydrate- 

 iodine the reaction begins in many of the grains in 30 sec- 

 onds. It is over in nearly all in 10 minutes and in all in 

 20 minutes. The reaction starts at the most promi- 

 nent points on the margin, which become dark and swell 

 somewhat, and the process goes inward from these points 

 all over the grain. The gelatinized grains are not very 

 large and usually have a central light space surrounded 

 by a thick, dark marginal band. They retain much of 

 their original form. 



The reaction with chromic add begins in most of the 

 grains in 30 seconds, and is over in 4 minutes. The cen- 

 tral part of the grain becomes clearer, and clear lines 

 extend from this part to each angle, attended by gelat- 

 inization of the interior and swelling of the grain; but 

 the starch between these lines retains for a time its original character. The capsule of the grain 

 dissolves atone point and the contents flow out. The solid more resistant starch before noted then 

 slowly dissolves, and finally the entire grain disappears. 



With pyrogallic add the reaction begins in many grains in 30 seconds and is over in 10 minutes. 

 The central part of the grains becomes clear, and clear lines extend from it to each angle, but the 

 starch between these lines is more resistant. The grain swells, and the ungelatinized resistant 

 portions are forced further and further apart; finally, they also become gelatinized and a large 

 capsule is formed that is filled with a semifluid mass. The gelatinized grains are large and retain 

 some of their original form. 



The reaction with ferric chloride begins in many grains in 30 seconds and is over in 10 minutes. 

 The central part of the grain grows larger and clearer, and the whole grain swells, usually suddenly 

 and very rapidly. In some grains the angles become gelatinous first, this being followed by a clear- 

 ing of the central part and swelling of the grain. The starch between the angles is usually gelati- 

 nized after the other part. The gelatinized grains are large and rather irregular in outline, but 

 they retain some of the original form of the grain. 



The reaction with Purdy's solution begins in some of the grains in one minute, and a few are 

 completely gelatinized in 10 minutes, but there is little further progress in an hour. The reaction 

 appears to be the same as that with pyrogallic add. 



GENUS TRITICUM. 



The genus, as now limited, comprises ^gilops and Trilicum. The former includes twelve 

 species which grow wild in Southern Europe and in parts of Asia, one of which is believed to be the 

 probable source of our cultivated wheats. The polymorphous Triticum includes among its number 

 three species of cultivated wheats {T. monococcum Linn., T. polonicum Linn., and T. sativum Lam.). 

 The many varieties of T. sativum are classified in three races — the spelts, the emmers, and the wheats. 

 The starch of an agricultural variety of the common wheat (7'. vulgare Vill.) and that of one of the 

 emmers (T. dicoccum Schrank) were examined as types of those races. 



STARCH OF TRITICUM SATIVUM VAR. VULGARE. (Plate 2, figs. 9 and 10. Chart 15.) 



Histological Characteristics.— In form the grains are simple and isolated, excepting a few that 

 are found in aggregates and clumps. There are two distinct classes of grains, large and small. The 

 conspicuous forms of the large grains are nearly round, oval, and irregular ovoid. AVhen viewed 



