GENUS NYMPH^A. 841 



The grains vary in size; the smaller are 3 by 3;u; the larger arc 27 by 24(1 in length and breadth. 

 The common size is 19 by 16ju in length and breadth. 



Polariscopic Properties. The figure is eccentric except in the relatively few round grains, in 

 which it may be centric. Its lines are distinct and broader, tliough less clear-cut at the margin; 

 usually straight, but may be bent, of irregular thickness, or rarely bisected. 



The degree of pohrization is fair to high, varying somewhat in the same aspect of one grain, 

 in different aspects of a given grain, and in different grains. 



With selenite in most grams the quadrants are well defined, irregular in shape, and unequal in 

 size. The colors are usually pure. 



Iodine Reactions. With 0.25 per cent Lugol's solution the grains all color a fair blue-violet; 

 with 0.125 per cent solution they color very lightly and the color deepens slowly. After heating in 

 water until the grains are completely gelatinized, the solution colors lightly and the gelatinized grains 

 very deeply on the addition of iodine. After boiling for 2 minutes, the solution colors very deeply and 

 the grain-residues fairly. The capsules are all colored a red-violet when an excess of iodine is added. 



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

 utes are lightly stained. 



With safranin the grains begin to stain lightly at oucc and in 30 minutes are fairly stained. 



Temperature Reaction. The temperature of gelatinization is 68 to 70 C, mean 69. 



Effects of Various Reagents. With chloral hydrate-iodine the reaction begins in a few grains, 

 which are probably injured or in the process of digestion, in 30 seconds and in all the rest in 1}^ min- 

 utes. About half of the total number are gelatinized in 6 minutes, nearly all in 10 minutes, and all 

 in 15 minutes. The reaction begins at the distal end of the grains, the starch becoming dark and 

 swelling. The whole margin then darkens and the process proceeds inwards, but more rapidly usu- 

 ally from the distal end and one side than from the rest of the margin. Just before the starch sur- 

 rounding the hilum becomes much involved in the reaction, a bubble at the hilum begins to increase 

 in size, and as the grain becomes more and more gelatinous the bubble increases to a great size. 

 Finally, when the whole grain is darkened and presumably gelatinous, the bubble decreases in size 

 and finally disappears. The gelatinized grains are fairly large and retain much of their original form; 

 they show a central, round light portion surrounded by a dark band. 



The reaction with chromic acid begins in some grains in 10 seconds, in the rest in 20 seconds, and 

 is over in 2 minutes. The starch about the hilum becomes gelatinous and fine striae appear radiating 

 from the hilum throughout the grain. The grain swells rapidly and the less resistant starch passes 

 into a semifluid mass in the center; the resistant starch forms a thick, coarsely striated band at the 

 margin. This band is often divided into an inner and an outer portion, and the inner portion is 

 divided by coarser striae than the outer, and disappears as the grain continues to swell, while the 

 outer portion forms a thin, homogeneous-looking capsule. Finally, this capsule dissolves at one 

 point, usually the distal end. The semifluid starch within flows out and is dissolved, followed by 

 solution of the rest of the capsule. 



Reaction with pyrogallic acid begins in 20 seconds and is over in 23^ minutes. The starch about 

 the hilum is transformed into a gelatinous mass and fine striae appear radiating from the hilum 

 throughout the grain. The less resistant starch is changed into a gelatinous mass which occupies 

 the irmer portion of the grain, and the more resistant starch forms a thick, striated band at the mar- 

 gin which becomes divided into an inner and an outer portion. The inner portion is not so dense 

 and is more coarsely striated than the outer, and as the reaction progresses it is gelatinized. The 

 outer portion remains, but as the grain swells it becomes thinner, less dense and homogeneous, until 

 it has the form of a thin, transparent capsule which is much folded and crumpled. The gelatinized 

 grains are very large and are distorted. 



Reaction with ferric chloride begins in a few grains in 30 seconds, and is over in 13 minutes. A 

 bubble appears at the hilum, and a very narrow marginal portion grows darker and somewhat clearer 

 than the other part of the grain. The distal end shows slight fissures, and from these there is a protru- 

 sion of gelatinous material. The reaction progresses from these points to all parts of the distal end, 

 until all the starch at this point is changed into a gelatinous mass inclosed in a thin, transparent, much 

 folded, and wrinkled capsule. From the distal end the reaction progresses proximally until it nearly 

 reaches the hilum, when the bubble, which is usually at the hilum, begins to increase in size, and then 

 the whole proximal end of the grain swells. The more resistant starch is converted into a gelatinous 

 marginal band, and while this is taking place the bubble at the hilum, having reached a large size. 



