GENXI8 VICIA. 381 



iodine. After boiling for 2 minutes the solution colors a deep indigo-blue and the grain-residues a 

 bright blue of much lighter color. The capsules are colored a deep reddish-purple with an excess 

 of iodine. 



Staining Reactions. — With gentian violet the grains begin to stain in a minute and in 30 minutes 

 they are very lightly stained, slightly less than the grains of V. sativa. 



With safranin the gi'ains begin to stain at once and in 30 minutes they are lightly stained, 

 slightly less than the grains of V. sativa. 



Temperature Reaction. — The temperature of gclatinization is 65° to 07° C, mean 06°. 



Effects of Various Reagents. — With chloral hydrate-iodine some of the grains begin to react in 

 20 seconds. About one-third are gelatinized in 5 minutes, two-thirds in 15 minutes, four-fifths in 30 

 minutes, and nine-tenths in an hour. The reactions are the same qualitatively as those of V. sativa. 



The reaction with chromic acid begins in some grains in 15 seconds and in all in 45 seconds. It is 

 over in most in 1^ minutes and in all in 2J/^ minutes. It is the same qualitatively as that of V. sativa. 



With pyrogallic add the reaction begins in most of the grains in 15 seconds and is over in all 

 in 13^ minutes. It is the same qualitatively as that of the grains of V. sativa. 



The reaction with ferric chloride begins in a few grains in a minute. About two-thirds are com- 

 pletely gelatinized in 15 minutes and practically all in 40 minutes. It is the same qualitatively as 

 of V. sativa. 



The grains begin to react in a minute with Purdy's solution. About three-fourths are completely 

 and all but a few are partially gelatinized in 8 minutes, and all are completely gelatinized in 20 

 minutes. The reaction is the same qualitatively as of V. sativa. 



STARCH OF VICIA FABA. (Plate 4, figs. 23 and 24. Chart 33.) 



Histological Characteristics. — In form the grains are simple and isolated. In a few grains well- 

 marked depressions divide the grain into several distinct portions, each of which has its central 

 cavity, irregular fissures, or hilum, thus suggesting a compound grain. The conspicuous forms are 

 the ovoid to oval and elliptical. There are in addition reniform, pyriform, triangular, and quad- 

 rangular with rounded angles, and spherical forms, the latter especially among the smaller grains. 

 The grains are in many cases about two-thirds as thick as they are broad. 



Most of the grains are so subdivided by cavities and irregular fissures that no hila can be demon- 

 strated. Characteristically the fissuration in the ovoid to elliptical grains takes the form of a very 

 prominent single fissure which runs the length of the grain, with many side fissures branching from it. 



The lamellcE are not visible in most of the grains, but in some they may be seen to be rather 

 coarse, continuous rings which follow closely the outline of the grain. The absence of demonstrable 

 hila and of multiple systems of lamellae indicate that the grains are simple. There are from six to 

 eight lamellae on the larger grains. 



The grains vary in size from the smaller, which are 5 by i/x in length and breadth, to the larger, 

 which are 42 by 28m in length and breadth. The common size is 29 by 22/i in length and breadth. 



Polariscopic Properties. — The figure is centric or slightly eccentric. It is distinct, but not 

 clear-cut. The lines composing it are usually straight, but on account of the fissures and cavities 

 in most of the grains its exact character can not be determined. In general characters it agrees 

 with that of V. villosa. 



The degree of polarization is high, as a rule. It varies somewhat in different grains, and it is 

 higher in the same grain when seen on end or edge. It is higher than that of V. sativa. Very often 

 there is a large dark area corresponding to the point of intersection of the lines. 



With selenite the quadrants, which often can scarcely be recognized as such, are not well defined, 

 irregular in shape, and unequal in size, and sometimes subdivided. The colors are generally pure, 

 particularly the blue. 



Iodine Reactions. — With a 0.25 per cent Lugol's solution the grains all color a fairly deep blue 

 or pinkish-violet; with a 0.125 per cent solution they all color fairly. The color is deeper than that 

 of V. sativa. After heating in water until all the grains are completely gelatinized, both the solu- 

 tion and the gelatinized grains color deeply on the addition of iodine. After boiling for 2 minutes 

 the solution colors very deeply and the grain-residues fairly. The capsules all color a violet with 

 an excess of iodine. 



Staining Reactions. — With gentian violet the grains begin to stain very lightly at once and in 30 

 minutes they are rather lightly stained. The stain is deeper than that of V. sativa. 



