OENTTS IRIS. 



689 



PS CI PA 

 PC PS 



the shape and irregularity of the grain, and are probably incomplete near the distal end. One or 

 more secondary sets of lamelte are frequently observed at varying angles to the primary set. 



The grains vary in size; the smaller are 6 by 4/^; the larger are 30 by 16^ in length and breadth. 

 The common size is 18 by 10// in length and breadth. 



Polariscopic Properties. — The figure is usually eccentric and distinct in most of the grains. 

 Its lines are rather fine, often bent, sometimes bisected. It is fairly clear-cut, distinct, but generally 

 irreg\ilar. 



The degree of polarization is fair. It varies somewhat in the different grains and in the same 

 aspect of a given grain. 



With selenite the quadrants are fairly well defined, generally irregular in shape, and unequal in 

 size. The colors are generally pure, the blue being quite pure, but the yellow sometimes not. 



Iodine Reactions. — with 0.25 per cent Lugol's solution the grains all color a fairly deep violet; 

 with 0.125 per cent solution they color rather lightly at 

 first, and the color does not deepen rapidly. After heat- 

 ing in water until the grains are completely gelatinized 

 the solution colors fairly deeply and the gelatinized grains 

 very deeply on the addition of iodine. After boiling for 

 2 minutes the solution colors very deeply, but most of 

 the grain-residues do not color at all. The capsules color 

 a deep red-violet to wine-red with an excess of iodine. 



Staining Reactions. — ^With gentian violet and with saf- 

 ranin the grains all begin to stain at once and in 30 min- 

 utes they are lightly stained. 



Temperature Reaction. — The temperature of gelatin- 

 ization is 71° to 72° C, mean 71.5°. 



Effects of Various Reagents. — With chloral hydrate- 

 iodine a few grains begin to react in 30 seconds, and all 

 are gelatinized in 5 minutes. The reaction begins at the 

 distal end of the simple grains and also at the free edges 

 of any of those portions which have probably been added 

 last. These points become dark and swell slightly, and 

 usually the starch at the proximal end becomes dark 



and swells slightly. The process now advances inward from these two points over the rest of the 

 grain, but there is not much swelling until the starch of the greater part of the grain becomes dark. 

 There is usually a line of demarcation between the gelatinized and the non-gelatinized portions of 

 the grain. The gelatinized grains are fairly large, of a uniform dark color, and retain much of their 

 original form. 



The reaction with chromic acid begins in 5 seconds and is complete in 25 seconds. It is so rapid 

 that it is impossible to distinguish all the steps, but in general it appears to consist in the gelatini- 

 zation of the inner part of the grain in that portion between the hilum and the distal end, and also 

 of all the starch at the distal end. These parts of the grain become granular and pass into a semi- 

 fluid mass, and the whole grain swells, only a thin layer remaining at the distal end. The margin, 

 except at the distal end, is formed of a fairly thick, striated band which shows the remains of some 

 lamellae. This band becomes thinner and homogeneous, and finally the layer at the distal end is 

 dissolved, opens out, and the gelatinous starch within flows out and dissolves. 



Reaction with pyrogallic acid begins in 10 seconds and is over in a minute. The hilum swells 

 somewhat and two lines appear, one on each side of the hilum, which run towards the distal end. 

 Between these two lines the starch becomes granular and then gelatinous, and the grain swells, 

 especially in the direction of the longitudinal axis. The more resistant starch forms a band at the 

 margin which is thicker at the proximal than at the distal end, and shows striae and the remains 

 of the lamellae. This band becomes thinner and homogeneous in appearance as the grain swells 

 and is especially thin at the distal end. The gelatinized grains are large, much twisted, folded, 

 and convoluted at the distal ends and retain some of their original shape at the proximal end. 



The reaction with ferric chloride begins in many grains in 30 seconds and is over in 6 minutes. 

 The reaction begins at the distal end. The starch at the squared corners becomes gelatinized and 

 spreads out laterally, and later all the starch at the distal end becomes gelatinized and swells irreg- 



MINUTES 

 Curve of Reaction- 1 ntenaitiea of Starch of Iru florentina. 



