752 



STAECHES OF IRIDACE^. 



Chart No. 293. 



The degree of polarization is low to fair in most grains, and decidedly variable in different 

 grains and in different aspects of the same grain. 



With selenite the quadrants are not well defined, usually irregular in shape, and always unequal 

 in size. The colors are not pure. 



Iodine Reactions. With 0.25 per cent Lugol's solution the grains are colored at once fairly deeply; 

 with 0.125 per cent solution the coloration occurs immediately and deepens until it is nearly as deep 

 as that with the 0.25 per cent solution. After heating until all the grains are completely gelatinized, 

 the solution is colored lightly and the gelatinized grains deeply on the addition of iodine; these 

 grains (which are less deeply colored than others) have a pinkish capsule after the addition of an 

 excess of iodine. After boiling for 2 minutes the solution colors very deeply and the grain-residues 

 lightly. Most of the capsules contain some blue-reacting starch. When an excess of iodine is 

 added, some of the grain-residues have a violet-colored 

 capsule, some a blue-violet, and others a pinkish-violet. 



Staining Reactions. With gentian violet the grains 

 begin to stain immediately and after 30 minutes the color 

 is fair. 



With safranin the grains begin to stain immediately 

 and after 30 minutes they are fairly well stained. 



Temperature Reaction. The temperature of gelatin- 

 ization is 54.5 to 56.5 C, mean 55. 



Effects of Various Reagents. With chloral hydrate- 

 iodine some of the smaller grains begin to react in 30 

 seconds and in 2^2 minutes the reaction is general. All 

 are darkened and the reaction is over in 30 minutes. In 

 the reniform grains the reaction begins with swelling 

 at the base and spreads around the margin until it reaches 

 the two prominences at the side of the proximal end of 

 the grain. In the meanwhile the reaction spreads over 

 all of the inner part of the grain until only a small, 

 wedge-shaped portion is left about the hilum at the prox- 

 imal end, and this soon also becomes included. The gelat- 

 inized grains are fairly large and their distal ends show a concentric arrangement of rather irregular 

 dark bands separated by light fissures. The proximal portions generally appear as more or less 

 homogeneous dark masses divided by irregular fissures, in the same manner that the original grain 

 was fissured. They retain much of the original form of the grain. 



There is reaction with chromic acid in many grains in 20 seconds and it is over in all in 2J^ 

 minutes. The reaction appears to consist in a rapid breaking down of the whole substance of the 

 grain, beginning at the portion just beneath the hilum and extending towards the proximal end and 

 outward to the sides. The grain becomes a large, gelatinous mass consisting of a very thin homo- 

 geneous capsule inclosing a finely granular mass. The capsule is dissolved at one point and the 

 granular inclosed mass flows out and is dissolved, followed by solution of the capsule. 



With pyrogallic acid there is a general reaction in 30 seconds and it is over in 23^ minutes. 

 The reaction consists in a general breaking down of the grain into a finely granular mass, accompanied 

 by enormous swelling. This reaction begins in the portion between the distal end and the hilum, 

 and extends downward and outward, the part just above the hilum remaining unaffected at first, 

 but is pushed up to form a thick, marginal portion as the grain swells. Then the margin gradually 

 becomes thinner and transparent. The gelatinized grains are very large, much folded, and invag- 

 inated, and they do not retain much of the original form of the grains. 



The reaction with ferric chloride begins in 13^2 minutes. Most grains are gelatinized in 15 minutes 

 and all in 30 minutes. The margin up to the prominences at each side of the proximal end becomes 

 gelatinous. The process starts at the distal end of the grain and spreads upward. After these prom- 

 inences are reached the process spreads inward and at the same time a very small part of the proximal 

 end is involved, and finally there is formed an irregularly gelatinous, peripheral portion surrounding, 

 or almost surrounding, a non-gelatinized center. The center becomes invaded by small fissures which 

 divide it into small parts which separate and gelatinize independently. The gelatinized grains are very 

 large, somewhat irregular, and sacculated. They do not retain any of the original form of the grain. 



Curve of Reaction-Intensities of Starch of Cypella 

 herberti. 



