GENUS ARACHIS. 



415 



Curve of Reactioa-Intensities of Starch of Arachts 

 hypogcea. 



the grains color a very lifiht reddish-violet, which deepens rather quickly into a fairly deep reddish- 

 violet in 5 minutes. After heating in water until all the grains are gelatinized, the solution does 

 not color, but the gelatinized grains become a deep reddish-purple on the addition of iodine. If 

 the preparation is boiled for 2 minutes and then treated with iodine, the solution becomes a light 

 bottle-green and the grain-residues assume either a light reddish-violet or old-rose tint. When an 

 excess of iodine is added the grain-residues color a deep reddish-purple, and the capsules a deep old- 

 rose to a wine color. 



Slaining Reactions. — With gentian violet and with saf- 

 ranin the grains begin to stain very lightly at once and 

 in 30 minutes are lightly stained. 



Temperature Reaction. — The temperature of gelatin- 

 ization is 66° to 67° C, mean 66.5°. 



Effects of Various Reagents. — With chloral hydrate- 

 iodine reaction begins at once and is over in practically 

 all the grains in a minute. The reaction starts usually 

 at one point on the margin, at which the starch darkens 

 and swells somewhat. The rest of the marginal starch 

 then becomes affected and the process spreads inward. 

 When it nears the hilum a bubl^le often appears here, 

 swells, then shrinks and disappears. The reaction ap- 

 pears to spread more rapidly from the point first affected 

 than from other portions of the margin. Tlie gelatin- 

 ized grains are not very large and retain the original 

 form of the grain. They appear to consist of a rather 

 small, central, light area surrounded by a broad, dark 

 marginal band. 



The reaction with chromic acid begins at once and is over in 30 seconds. It is so rapid that the 

 principal steps can not be clearly distinguished. It appears that the less resistant starch is con- 

 verted into a semifluid mass in the interior of the grain, and the more resistant starch into a marginal 

 band. Then there is formed a thin capsule which is dissolved at one point, the semifluid mass 

 begins to flow out and dissolves, followed by solution of the remaining part of the capsule. 



Reaction with pyrogallic acid begins in a minute and is over in 5 minutes. The hilum becomes 

 very distinct and fine stria are seen to radiate from the hilum in all directions throughout the grain. 

 The less resistant starch forms a semifluid, swollen mass, which occupies the central part of the grain, 

 while the more resistant starch forms a broad, dense, finelj' striated, marginal band, which shows 

 the remains of the lamelhe in the form of two or three refractive and non-refractive parts. This 

 band becomes, rather slowly, less dense and less broad. The gelatinized grains are fairly large 

 and retain much of their original form. The capsule is thick and dense and not much wrinkled 

 or folded. 



With ferric chloride reaction begins in a few grains in 2 minutes and is over in 12 minutes. The 

 process starts at one point on the margin, usually the distal end, where the starch swells out irreg- 

 ularly. From here the reaction spreads over the adjacent starch, and then over the whole grain 

 until it reaches the vicinity of the hilum. At the hilum a bubble often forms which somewhat 

 increases in size, but soon shrinks and finally disappears. Such of the starch as remains ungelatin- 

 ized often splits into two or three pieces which separate and gelatinize independently of one another. 

 The gelatinized grains are very large and do not retain much of their original form. The capsules 

 are somewhat folded and crumpled. 



The reaction with Purdy's solution begins in a few grains in iK minutes and all the grains are 

 nearly completely gelatinized in 20 minutes. The reaction has the same characters as that with 

 pyrogallic acid. 



NOTES ON THE STARCHES OF LEGUMINOS^. 



In Vicia, Phaseolus, Muama, Dolichos, Lens, Lathyrus, and Pisum (the wrinkled peas excepted) 

 the starch-grains as a whole belong to a common type which may be designated the bean type, 

 both because of the conspicuousness of this form of grain in these genera and of the common resem- 

 blance between the shajie of the grain and the most familiar shapes of food beans. These grains 

 are characterized especially by an ovoid to elliptical and kidney-shaped form, commonly having a 

 deep, longitudinal fissuration which extends along a considerable length of the grain. 



