382 



STARCHES OF LEGUMINOSiE. 



Curve of Reaction-Intensities of Starch of Vicia faba. 



With safranin the grains begin to stain very lightly at once and in 30 minutes they are lightly 

 stained. The stain is more than that of V. sativa. 



Temperature Reaction. — The temperature of gelatinization is 64° to 66° C, mean 65°. 



Effects of Various Reagents. — With chloral hydrate-iodine some of the grains which are probably 

 injured or partly eroded begin to react at once, but other 

 grains which appear to be normal begin to react in 20 

 seconds. About one-fifth of the grains are gelatinized in 



5 minutes, two-thirds in 15 minutes, three-fourths in 30 

 minutes, and seven-eighths in an hour. The process may 

 begin at one or both ends. If it begins at one end, the 

 starch at this point becomes of a dark indigo color and 

 swells slightly, and the process spreads gradually over the 

 whole grain, more rapidly in the central portion than near 

 the margin. If it begins at both ends, the starch at these 

 points becomes of a dark indigo color and swells slightly, 

 and the process spreads gradually from over the whole 

 grain. The starch in the central portion is gelatinized 

 more rapidly than that at or near the margin, so that the 

 processes spreading from the two ends become united 

 through the central part of the grain, and later spreads over 

 the sides. The gelatinized grains are fairly large, but not 

 much distorted, and retain much of their original form. 



With chromic acid many of the grains begin to react 

 in 15 seconds and are dissolved in 13^ minutes. The 



remainder begin to react in 30 seconds to a minute, and are dissolved in 3 minutes. The central 

 fissure or group of fissures and hila becomes distinct, and the starch surrounding it is seen to be 

 finely striated. Then as the starch nearest the mesial fissure is transformed into a semiliquid mass 

 the whole grain begins to swell, and most of the remaining ungelatinized starch is also rapidly trans- 

 formed into a semiliquid gelatinous mass, except the most resistant outer portion, which forms a 

 capsule. This capsule is now dissolved at one point and the semiliquid contents flow out and pass 

 into solution. Other parts of the capsule are dissolved later. 



The reaction with pyrogallic acid begins in from a few seconds to 13^ minutes and is over in 



6 minutes. It appears to consist of the gradual reduction of the less resistant starch to a semiliquid 

 mass, accompanied by slow swelling of the entire grain. The grain gradually becomes larger and 

 clearer, and the inner portion assumes the appearance of semitransparent masses of gelatinous 

 starch surrounded by numerous clear channels, while the marginal portion appears to consist of a 

 fairly broad, translucent, homogeneous-looking band of resistant starch which is often of very irreg- 

 ular form because of folds and indentations of the margin. 



With ferric chloride some of the grains begin to react in 1^ minutes. About one-third are 

 gelatinized in 15 minutes and two-thirds in 50 minutes. The reaction is complete in an hour. The 

 process may begin at one or both ends of the grains. If the former, the starch at this point becomes 

 gelatinous and swells irregularly, and the reaction spreads over the rest of the grain about as rapidly 

 over one part as over another. If the reaction begins at both ends, the starch at these points becomes 

 gelatinous and swells irregularly, and then spreads over the rest of the grain until often only a 

 small, central, unswoUen portion is left that is surrounded or nearly surrounded by gelatinized 

 starch. This center is also finally gelatinized. The gelatinized grain is very large and irregularly 

 shaped, and the capsule is wrinkled, sacculated, and crumpled. 



Most of the grains become clearer with Purdy's solution, and the central fissure, or fissures, or 

 hila, or cavities become very distinct and somewhat larger in a minute. In 10 minutes the majority 

 of the grains are nearly completely gelatinized, and in 15 minutes all are nearly completely gelatinized. 



STARCH OF VICIA FULGENS. (Plate 5, figs. 25 and 26. Chart 34.) 



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

 a few which occur in aggregates. The surface of the grains is somewhat irregular, owing to indenta- 

 tions and elevations. The conspicuous forms are bean-shaped, elongated, irregular and regular 

 oval, ovoid, and rounded. There are also forms which are irregular rhomboidal, polygonal with 



