GENUS VICIA. 



379 



Chart No. 31. 



PC PS 

 5 



it was in the form usually of a Ions, broad line with bisected ends occupying the long diameter 

 of the grain, or a cross, commonly with a large ilark area at the intersection of the lines. Tlie lines 

 are generally broad and not clear-cut. The mesial line with bisected ends is very conspicuous and 

 may be referred to as the bean ty]3e. 



The degree of polarization is high, as a rule, although it is absent in some places because of 

 irregularities, such as depressions and fissures on the surface of the grains. It is iiigher when the 

 grain is viewed from etlge or end. 



With selenite the quach-ants are well defined, but irregular in shape, very unequal in size, and 

 often subdivided. The colors as a rule are pure or fairly pure. 



Iodine Reactions. With a 0.2.5 per cent Lugol's solution, the grains color a fairly deep blue- 

 violet; with a 0.125 jier cent solution, the grains are at first tinteil ligliMy and the color deepens 

 somewhat. After heating in water until all the grains 

 are completely gelatinized, the solution is quite deeply 

 colored and the capsules very deeply on the addition of 

 iodine. The grains are much swollen and distorted. 

 After boiling for 2 minutes tlie solution becomes more 

 deeply colored, but the grain-residues much less deeply. 

 With an excess of iodine most of the capsules become a 

 violet color, and usually inclose some blue-reacting 

 starch. 



Staining Reactions. With gentian violet the reac- 

 tion begins immethately in some of the grains, while 

 otliers are only very lightly stained after 114 minutes. 

 In 30 minutes the color is scarcely deeper than at the 

 beginning. The partially gelatinized grains are more 

 deeply stained than the uninjured grains. 



With safranin the reaction begins in IJ^ minutes, 

 but after 30 minutes the color is light. 



Temperature Reaction. The temperature of gelatini- 

 zation is 72 to 73 C, mean 72.5. 



Effects of Various Reagents. With chloral hydrate- 

 iodine the reaction begins in some of the grains in 30 seconds. About half are gelatinized in 30 

 minutes, two-thirds in 15 minutes, three-fourths in 30 minutes, and nine-tenths in an hour. Both 

 tlie hilum or tlie fissures or spaces representing tlie hilum and the lamella' are rendereil very distinct. 

 Gelatinization begins by tlie darkening of one end, the process spreading rapidly over the wliole grain 

 and attended l^y slight and uniform swelling. When the whole grain has darkened, swelling con- 

 tinues evenly. The gelatinized grains are in the form of an irregular mass in which the center is 

 separtited more or less completely from the dark marginal ring by a lighter space. The marginal 

 ring shows alternate light and dark concentric bands. The swollen grains are not much distorted, 

 nor very large. 



The reaction with chromic acid begins immediately in some of the grains, and in 30 seconds in 

 all. It is over in 5 minutes. Botli hilum and Jamelke are very distinct. The reaction begins by 

 fissuring of tlie liilum or region of tlie hilum, and frequently by an extension of radial fissures tlirough- 

 out the grain. The region of the liiluni swells, and the more resistant stai-ch of the outer part of 

 the grain is formed into a ring which shows fine strise and concentric, alternate, refractive and 

 non-refractive lines, and also occasionally irregular granules on the inner side. This ring becomes 

 clear and thinner as the grain continues to swell, until a large, ovoid, thin-walled mass is formed. 

 All parts of the gelatinized grain dissolve with the same readiness. 



The reaction with pijrogallic acid begiiLS in all in 30 seconds and it is over in 5 minutes. Both 

 hilum and lamellai are rendered very distinct. The reaction begins in a swelling of the hilum; the 

 inner part of the grain becomes a finely granular mass; and the marginal jiortion is changed to a 

 distinctly striated ring that is marked with concentric light and dark lines. Tiiis ring may become 

 invaded Ijy deep, stellate fissures as the grain continues to swell. The gelatinized grain is very large 

 and much distorted by many rounded, small, saccular projections at the margin. 



With ferric chloride the reaction begins in a few grains in a minute and about two-fiftlis are 

 completely gelatinized in 13 minutes. Other grains are not affected at all even after an hour. Both 



MINUTES 

 Curve of Reaction-Intensities of Starch of Vicia sativa. 



