738 



STARCHES OF IRIDACE^. 



With pyrogaUic add some grains begin to react in 2 minutes. All are affected in 30 minutes 

 and half are entirely gelatinized. The hilum and lamellse become more distinct, and a line or fissure 

 extends from each side of the hilum to the corners of the facets. Fine strise appear radiating from the 

 hilum throughout the grain, the hilum begins to swell, and the lines radiating from it open out 

 at the same time. The inner parts pass into a gelatinous mass, while the marginal portions form a 

 finely striated ring which shows, in some parts refractive and non-refractive bands. This ring grows 

 thinner and clearer. The gelatinized grains thus formed are swollen to about 1.5 times or twice 

 the size of the original and are not much folded or crumpled, but retain somewhat the original 

 form of the grain. 



The reaction with ferric chloride begins in some of the smaller grains in 2 minutes and is com- 

 plete in 30 minutes. The hilum becomes very distinct, but the lamellae entirely disappear. In those 

 grains in which the reaction is rapid the whole grain becomes very clear, the inner portion is changed 

 into a gelatinous mass, and the entire grain swells slowly until a relatively large mass is formed 

 which retains in general the original shape of the grain. In the grains that react more slowly lines 

 are seen running from the hilum to the corners of the facets; the marginal portion becomes clearer 

 and darker; and the lamellae reappear in this marginal part. The grain now begins to swell, the 

 inner part being converted into a gelatinous mass, which is inclosed by a striated marginal ring, 

 which becomes thinner and more transparent. The gelatinized grains are large and smooth, and 

 retain somewhat the original form of the grain. 



The reaction with Purdy's solution begins in some grains in IJ^ minutes and is complete in 

 half the total number in 45 minutes. The hilum and lamellae become more distinct and two lines 

 extend from the hilum to the comers made of the facets. The inner part of the grain is transformed 

 into a gelatinous mass, and the more resistant marginal part forms a ring which is striated and 

 shows concentric refractive and non-refractive bands. Just inside the outer marginal ring there 

 is often a darker, somewhat striated, and fissured ring. Further changes consist in the gradual 

 clearing and thinning of both marginal rings to form a gelatinous capsule. The gelatinized grains 

 thus formed retain much of the original form of the grain. 



STARCH OF FREESIA REFRACTA VAR. LEICHTLINII. (Plate 73, figs. 435 and 436. Chart 286.) 



Histological Characteristics. — In form the grains are simple and occur isolated or in aggregates 

 of two or more components, which may be of equal or unequal size. All the isolated grains that 

 have been parts of aggregates are marked by pressure facets. The surface tends to roundness and 

 smoothness. The conspicuous forms are hemispherical 

 with one to three facets at the distal end; also spherical 

 or nearly spherical, ovoid, and polygonal. A few grains 

 may be seen marked over the entire surface with pressure 

 facets. The grains are not flattened, and on end they 

 appear spherical in shape. 



The hilum is a fairly distinct, relatively large, non- 

 refractive spot, usually centrically placed and in the 

 median line. There may be double hila, and 2 or more 

 may be noted in aggregates. The hilum is rarely fissured, 

 and if so the fissuration is slight and of variable form. 



The lameUce are indistinct, and when they can be 

 clearly seen they appear as fine, regular, concentric rings 

 which follow the outline of the margin of the grain, being 

 more distinct as they are near the margin. One about 

 the center of the space between the hilum and the margin 

 is commonly very distinct. They appear to average 

 about 10 to 12 to a medium-sized grain. 



The grains vary in size from 2 to l^n. The common 

 size is about lO/i. 



Polariscopic Properties. — The figure is usually centric, distinct, and fairly well defined, but 

 the lines are generally somewhat broader near the margin and sometimes bent. 



The degree of polarization is fairly high, varying somewhat in different grains and in different 

 aspects of the same grain. It is higher at the proximal than at the distal end. 



Chart No. 286. 



P I GV 



s 



PS CI PA I 

 - PCPS 



Curve of Reaction-Intensitiea of Starch of Freesia 

 refracta var. leichtiinii. 



