RICHARDIA. 



719 



usually fine and intersect either at right angles or 

 obliquely. They are generally straight and often with 

 broadening at margin, but they may be bent and bisected. 

 Double and multiple figures are occasionally observed. 



The degree of polarization is moderate to high (value 

 70). It varies in the different grains from moderate to 

 high with more of the latter. A variation is also often 

 found in the same aspect of a given grain, or one quad- 

 rant may be moderate or even low, while the remainder 

 are high. 



With selenite the quadrants in most of the grains 

 are moderately clean cut quite clean cut in the larger 

 permanently isolated grains. In the majority of grains 

 they are slightly irregular in shape and somewhat un- 

 equal in size, but often regular and equal in the perma- 

 nently isolated grains. The blue is generally pure, but 

 the yellow is frequently impure. 



IODINE REACTIONS. 



With 0.25 per cent Lugol's solution the grains imme- 

 diately color a moderate blue-violet (value 45), which 

 deepens rapidly, becoming bluer in tint. With 0.125 per 

 cent Lugol's solution they color a light blue-violet, which 

 deepens rapidly, becoming bluer in tint. After heating 

 in water until the grains are gelatinized and then adding 

 a 2 per cent Lugol's solution, some of the grains color a 

 moderate and most of them a moderately deep indigo- 

 blue; and the solution a moderately deep indigo-blue. 

 If the preparation is boiled for 2 minutes and then treated 

 with an excess of 2 per cent Lugol's solution, the grain- 

 residues color a light to moderate blue, more of the 

 latter, most of them with a reddish tint; the capsules 

 become a deep old-rose to a deep reddish-heliotrope, with 

 many of the latter; and the solution a deep indigo-blue. 



ANILINE REACTIONS. 



With gentian violet the grains color very faintly at 

 once, and in half an hour they are lightly stained 

 (value 30). 



With safranin the grains color very lightly at once 

 and in half an hour they are lightly stained (value 33). 

 The grains color a little deeper with safranin than with 

 gentian violet. 



TEMPERATURE REACTIONS. 



The majority of the grains are gelatinized at 75 to 

 76 C., and all at 77 to 78.5 C., mean 77.7 C. 



EFFECTS OF VARIOUS REAGENTS. 



The reaction with chloral hydrate begins immediately. 

 Complete gelatinization occurs in about 88 per cent of 

 the entire number of grains and 95 per cent of the total 

 starch in 3 minutes; in about 98 per cent of the grains 

 and more than 99 per cent of the total starch in 5 min- 

 utes. ( Chart D 545.) 



The hilum becomes very prominent and a bubble is 

 often formed there. Many grains, practically all, have 

 pressure facets at the sides and distal ends; two lines 

 or canals are seen to extend from the hilum to the cor- 

 ners of the pressure facets. No lamellae are visible. A 

 narrow refractive band is formed rather slowly about 

 the margin of the more resistant grains. Gelatinization 

 begins in the smaller grains, and in the larger less re- 

 sistant grains, in all parts of the interior of the grain 

 at once. In the more resistant grains, it begins either at 



the distal corners at the end of the two canals already 

 mentioned in connection with the hilum, or, occasionally, 

 at the proximal end. According to the first method, the 

 entire grain becomes gradually more transparent and 

 gelatinous in appearance and at the same time swells 

 equally in all directions. According to the second, the 

 marginal starch at the facet corners gelatinizes, then the 

 two canals and the hilum become broader, thus causing 

 the grain to lengthen transversely, and dividing the 

 starch of the grain into two parts; of these parts, the 

 proximal or larger is usually gelatinized before the distal. 

 According to the last method the proximal margin be- 

 comes gelatinized first, and gelatinization proceeds from 

 this point evenly and equally over the whole grain. If a 

 bubble is present at the hilum, it shrinks and disappears 

 when the hilum is reached in the progress of gelatiniza- 

 tion. The gelatinized grains are moderately large and 

 somewhat distorted, but retain much resemblance to the 

 form of the untreated grain. 



The reaction with chromic acid begins in half a 

 minute. Complete gelatinization occurs in about 0.5 per 

 cent of the entire number of grains and 2 per cent of the 

 total starch in 5 minutes; in about 2 per cent of the 

 grains and 45 per cent of the total starch in 15 minutes; 

 in about 42 per cent of the grains and 96 per cent of the 

 total starch in 30 minutes; in about 80 per cent of the 

 grains and 98 per cent of the total starch in 45 minutes; 

 complete gelatiuization with the exception of a portion 

 of the margin of rare grains and over 99 per cent of both 

 the grains and total starch in 60 minutes. (Chart 

 D546.) 



The hilum does not become distinct until gelatiuiza- 

 tion has begun, and then two canals or fissures may 

 sometimes be seen extending from the hilum to the distal 

 pressure-facet corners, and in other grains there may be 

 seen irregular fissures extending into the body of the 

 grain. The lamellae are usually not visible, but in some 

 grains evidences of a lamellar structure may be made out 

 as gelatinization progresses. Gelatinization begins at the 

 hilum and is accompanied or preceded by the appearance 

 of a number of striae radiating from the hilum to the 

 margin, which divide the starch of the grain into long, 

 fine spicules. As the hilum enlarges, deep irregular 

 cracks extend from it into the body of the grain. The 

 ungelatinized starch collects at the margin in a striated 

 band which becomes more and more nearly transparent, 

 and small cracks invade the grain from the margin at 

 which points gelatinization proceeds more rapidly. In 

 some grains these cracks undoubtedly mean a dissolution 

 of the capsule and a final dissolution of the grain, but 

 in others the capsule appears to remain unbroken; and 

 these remain as thin-capsuled, very transparent com- 

 pletely gelatinized grains which do not retain much of 

 the form of the untreated grain. 



The reaction with chromic acid advances uniformly 

 in a number of grains until a few of the outermost lamellse 

 are reached; these layers for a while are quite resistant, 

 which results in making the percentage of grains com- 

 pletely gelatinized quite low while that of the total starch 

 is relatively high. Between the observations of 15 and 30 

 minutes these resistant outermost layers become gela- 

 tinized in many grains and hence at 30 minutes a rela- 

 tively large percentage of the entire number of grains 

 is completely gelatinized; and as the reaction advances 



