372 



STAECHES OF GRAMINACEiE. 



Differeniiation of the Starches of the Genus Secale. — Continued. 

 Errucre of Various Reagents.— Continued. Effects of Various Reaqents. 



Reaction with Chromic Acid. 



Mammoth Winter rye: Begins in 10 to 20 seconds; com- 

 plete in all in 2 )i minutes. 



Spring rye: Begins in 20 to 30 seconds; complete in all 

 in 2 minutes. 



Reaction with Pyrogallic Acid. 



Mammoth Winter rye: Begins in 30 to 45 seconds; com- 

 plete in all in 1 Ji minutes. 



Spring rye: Begins in 10 to 30 seconds; complete in all 

 in IJ^ mmutes. 



-Continued. 



Reaction with Ferric Chloride. 



Mammoth Winter rye: Begins in a few in 1}^ minutes; com- 

 plete in half in 30 minutes, and in nearly all in an hour. 



Spring rye: Begins in a few in a minute; complete in about 

 two-thirds in 30 minutes, and in nearly all in an hour. 



Reaction with Purdi/s Solution. 



Mammoth Winter rye: Begins in some in a minute; a 

 few partially gelatinized in 20 minutes, and but 

 little further change in an hour. 



Spring rye: Begins in some in a minute; little further 

 change during an hour. 



NOTES ON THE STARCHES OF SECALE. 



The two starches examined do not exhibit any appreciable differences in their gross liisto- 

 logical characters. In the reactions it is seen that the Mammoth Winter rye has a lower degree of 

 polarization, lower reactions with the aniline dyes, a lower temperature of gelatinization (1°), a 

 higher sensitivity to chloral hydrate-iodine and Purdy's solution, and a lower sensitivity to chromic 

 acid, pyrogallic acid, and ferric chloride. 



GENUS HORDEUM. 



This genus comprises about twelve known species. The origin of Hordeum sativum Jess., the 

 cultivated barley which occurs in various agricultural forms, is yet unknown, but according to 

 Hackel it originated from H. sponlaneum C. Koch, "which grows wild from Asia Minor and Cauca- 

 sian countries to Persia and Beloochistan, as well as in Syria, Palestine, and Arabia Petrsca.." An 

 agricultural form of H. sativum known as Champion barley was used as a type of the genus. 



STARCH OF HORDEUM SATIVUM VAR. (CHAMPION). (Plate 3, figs. 13 and 14. Chart 19.) 



Histological Characteristics.- — In form the grains are simple and isolated, with the exception 

 of a few in the form of aggregates and clumps. The aggregates consist generally either of numerous 

 grains of variable size, or of one large grain with very small grains closely adherent. The conspicu- 

 ous forms of the large grains are round, oval, ovoid, and reniform. When viewed on edge they are 

 spindle-shaped, elliptical, or occasionally plano-convex. In addition, triangular forms with rounded 

 angles and sides may be observed. The minute grains are usually globular, but are sometimes 

 spindle-shaped or oval. Hemispherical and dome-shaped grains are also present among both the 

 large and small grains. The starch of barley closely resembles that of wheat, but the grains are 

 not so large, and more reniform or bean-shaped forms are found. The large and small grains respec- 

 tively represent different forms of starch. 



The hilum is not usually visible, but it may occasionally be observed as a clear, round spot, 

 which is centric or slightly eccentric. Either a cavity or one or more clefts are rarely found in the 

 region of the hilum. When viewed on edge the longitudinal medial cleft or groove similar to that 

 noted in T. sativum var. vulgare is sometimes observed. 



The lameUcB are often invisible, but when observed they are rather coarse and complete con- 

 centric rings. On grains of common size from 6 to 8 lamellae have been counted. 



The grains vary in size from the smaller, which are 2 by 2/x, to the larger, which are 28 by 26/i. 

 The common size is 19^. 



Polariscopic Properties. — The figure is usually centric. It is distinct in the small grains, but 

 not well marked in the large ones. In the small grains the lines of the figure are rather thick and 

 commonly straight. In the large grains they are generally more distinct towards the margin, and 

 for the most part straight, although they may be bent and also bisected. The figure resembles 

 closely that of Triticum sativum var. vulgare, but is not quite so distinct in the large and more 

 irregular grains. 



The degree of polarization is low in the large grains to fairly high in the small grains. It is 

 higher at the margin than at the center in the large grains; and in some grains there is a variation 

 in the different quadrants. Polarization is fairly high when the grains are viewed on edge. On the 

 whole it is low. In some grains only parts of the extreme margin are anisotropic. 



