IRIS. 



637 



and in most it is moderate or moderately high. In 

 some it is lower between the two limbs of the cross 

 than elsewhere. 



With selenite the quadrants are usually clear-cut. 

 They are unequal in size and often irregular in form. 

 The colors are usually not pure. 



Iodine Reactions. 

 With 0.25 per cent Lugol's solution the grains all 

 color a light to moderate violet tinged with blue (value 

 40). The color deepens moderately rapidly until very 

 deep and more bluish. With 0.125 per cent Lugol's 

 solution the grains all color a light violet and the color 

 deepens rather slowly until moderately deep and more 

 bluish. After heating in water until all the grains are 

 completely gelatinized and then treating with a 2 per cent 

 Lugol's solution, the gelatinized grains are colored a 

 deep or a moderately deep indigo, and the solution a deep 

 indigo. If the preparation is boiled for 2 minutes and 

 then treated with an excess of a 2 per cent of Lugol's 

 solution, most of the grain-residues show only an empty 

 capsule, but in a very few the contents are colored a very 

 light indigo ; the capsules a deep wine-red ; and the solu- 

 tion a very deep indigo. 



Aniline Reactions. 



With gentian violet, the grains stain very lightly at 

 once, and in 30 minutes they are light to moderately 

 stained (value 40). Some grains are moderately stained 

 and some lightly, and the rest light to moderately. There 

 is no unevenness of coloring noted on the individual 

 grains. 



With safranin the grains stain very lightly at once, 

 and in 30 minutes they are moderately stained (value 

 45) . There are more moderately and moderate to lightly 

 stained grains than in gentian violet. 



Temperature Reactions. 

 The temperature of gelatinization of the majority of 

 the grains is 69° to 70° C, and of all is 71° to 72.5° C, 

 mean 71.75° C. 



Effects of Various Reagents. 



The reaction with chloral hydrate begins in 1 min- 

 ute. Complete gelatinization occurs in about 3 per cent 

 of the entire number of grains and 6 per cent of the total 

 starch in 5 minutes; in about 32 per cent of the grains 

 and 39 per cent of the total starch in 15 minutes ; in about 

 45 per cent of the grains and 50 per cent of the total 

 starch in 30 minutes ; in about 54 per cent of the grains 

 and 60 per cent of the total starch in 45 minutes; and 

 60 per cent of the gTains and 64 per cent of the total 

 starch in 60 minutes. (Chart D 379.) 



The hilum becomes distinct, attended in most grains 

 by the formation of a small bubble, which persists until 

 the hilum is reached in the process of gelatinization. 

 The lamella? are always rather indistinct, and become 

 obliterated as gelatinization progresses. The whole grain 

 becomes somewhat refractive, the first part of the grain 

 to show this is a broad band around the margin. Gela- 

 tinization begins at the distal corners of the grain just 

 above the margin. Two refractive cracks or fissures are 

 seen to separate the marginal portion at these points 

 from the rest of the grain and the marginal starch is 

 then gelatinized with considerable swelling and distortion 



of the capsule. Then the rest of the distal deposit 

 assumes a pitted appearance and is invaded on either side 

 by a longitudinal refractive fissure which extends about 

 two-thirds of the way to the proximal end. Between 

 these two fissures the starch becomes more and more 

 refractive, and is invaded in the interior but not on the 

 surface by several longitudinal refractive fissures, and 

 then divided by granules from these fissures into granules 

 of varying sizes and shapes. In the meantime gelatiniza- 

 tion has spread from the corners of the distal end all 

 along the distal margin and now extends toward the 

 proximal end, and the granules which have been pre- 

 viously formed are separated off and gelatinized. The 

 reaction proceeds more rapidly in the interior of the 

 grain than on the surface, which is proved by the fact 

 that before the hilum is reached on the surface, a 

 refractive canal or fissure is formed to the hilum in the 

 central part of the grain, the bubble swells and lengthens 

 out into this canal and sometimes passes through it 

 distally before shrinking and then disappearing, the 

 hilum enlarges considerably, and the surface and mar- 

 ginal material is at the same time rapidly gelatinized 

 except at the proximal margin, which is the last to be 

 broken down, and is often very resistant, remaining for 

 a long time after the rest of the grain is completely gela- 

 tinized. In a very few grains the proximal end is gelatin- 

 ized after gelatinization has progressed about half-way 

 between the distal end and the hilum, the most resistant 

 part in such cases being just distal to the hilum. 



The gelatinized grains are much swollen, have rather 

 thin capsules, and are very much distorted especially at 

 the distal end, and they retain very little resemblance 

 to the form of the untreated grain. 



The reaction with chromic acid begins in 1 minute. 

 Complete gelatinization occurs in about 1 per cent of the 

 entire number of grains and 6 per cent of the total 

 starch in 5 minutes; in about 6 per cent of the grains 

 and 70 per cent of the total starch in 15 minutes; in 

 about 24 per cent of the grains and 90 per cent of the 

 total starch in 30 minutes; in about 52 per cent of the 

 grains and 97 per cent of the total starch in 45 minutes; 

 in about 79 per cent of the grains and 99 per cent of the 

 total starch in 60 minutes. (Chart D 380.) 



The reactions with chromic acid are difficult to obtain 

 with any degree of satisfaction as in other species of irids. 

 The grains have a tendency to collect in groups (as in 

 many other species) and bubbles appear (as found in 

 many other species). These bubbles may either expand 

 or collapse, causing the grains in the field under obser- 

 vation to move from the field or crowd together. Since 

 there is always a tendency to some solution of the gTains 

 with chromic acid, when a new field must be sought at 

 30 minutes, as the result of movement from collapse of 

 bubbles, etc. ; it is impossible to compute the number of 

 grains with perfect accuracy since it is impossible to 

 determine what proportion has been dissolved. The wall 

 of some grains is very resistant, a small amount remain- 

 ing ungelatinized ; this may extend largely around the 

 margin or only at the proximal end and sides. 



Gelatinization begins rather slowly, and then the 

 process advances in most of the grains with considerable 

 rapidity, only a small amount of ungelatinized material 

 remaining in a few grains. 



