722 STARCHES OP IRIDACRB. 



deepens but little. After heating until the grains are completely gelatinized, the solution stains 

 fairly well and the grains very deeply on the addition of iodine. Grains not so deeply stained as 

 others show a violet capsule upon the addition of a slight excess of iodine. After boiling 2 minutes 

 the solution stains much more deeply, but the grain-residues much less. With excess of iodine 

 many capsules become a violet color and most of them contain blue-reacting starch. Some grains 

 are completely disintegrated. 



Staining Reactions. — ^With gentian violet and with safranin the grains begin to stain at once and 

 the color is fairly deep, but after 30 minutes the reaction is not much better than at first. 



Temperature Reaction. — The temperature of gelatinization is 75° to 76° C, mean 75.5°. 



Effects of Various Reagents. — With chloral hydrate-iodine reaction begins in some of the smaller 

 and medium-sized grains in 5 minutes, in others within 8 minutes, and all are darkened in 20 minutes; 

 the larger grains are not affected. The hilum becomes very distinct, but the lamella) are invisible. 

 The whole periphery darkens and the process extends inward from the margin without any swelling. 

 There is not a very sharp line of demarcation between the gelatinized and the non-gelatinized parts. 

 After the grain is darkened it swells slightly. The gelatinized grains formed are about twice as 

 large as the original grains and often show a light center with a dark marginal ring; they are not 

 distorted, and retain much of the original form. 



The reaction with chromic acid begins in a minute and is over in 43/^ minutes. The hilum 

 becomes very distinct, but not the lamellse. The hilum swells somewhat, the grain becomes striated, 

 and the inner part is converted into a gelatinous mass. The starch at the periphery forms a very 

 distinctly striated ring, ragged on the inner edge, and marked by alternate refractive and non- 

 refractive bands; this ring grows thinner as the grain swells and finally invaginates on one side, 

 continues to grow thinner and transparent, and finally disappears. 



Reaction with pyrogallic acid begins in IJ^ minutes and is over in 13 minutes. The hilum is 

 prominent, but the lamellae are not. The grain becomes covered by very coarse radiating stria;. 

 The inner part of the grain melts down slowly and evenly. The grain swells as the process pro- 

 gresses. The starch at the margin forms a ring which is very distinctly striated and shows alter- 

 nate refractive and non-refractive bands. The process did not go beyond this point. 



With ferric chloride a few grains begin to react in 13^ minutes. About three-fourths are affected 

 in 30 minutes and all are completely gelatinized in 40 minutes. The hilum is distinct and swells 

 somewhat, and the grain becomes covered with fine striae which grow coarser as the process goes on. 

 The inner portion passes into a gelatinous mass. The starch at the margin forms a striated ring with 

 a ragged, inner edge. This becomes thinner and transparent as the grain swells, until finally a large, 

 thin-walled, gelatinized grain is formed. These grains are large, somewhat infolded, but in general 

 retain the original forms of the grains. 



There is a very slight reaction with Purdy's sohdion in some grains in 5 minutes, but no further 

 change. The hilum and lamellae are both very distinct. The hilum swells somewhat and the grain 

 becomes covered by fine striae. A part of the inner starch may become gelatinous, but there is little 

 or no further reaction. 



STARCH OF WATSONIA IRIDIFOLIA VAR. O'BRIENI. (Plate 70, figs. 417 and 418. Chart 277.) 



Histological Characteristics. — In form the grains are simple, and many are to be seen in aggre- 

 gates consisting of two or three components, usually two. A few isolated grains have pressure facets, 

 as a rule one or two, usually one. The small grains are nothing like so numerous as in W. humilis. 

 The conspicuous aggregates are oval to elliptical and rounded to angular. Among the isolated 

 grains are noted spherical, dome-shaped, distorted spherical, hemispherical, and polygonal. The 

 grains are not flattened in any diameter, and appear spherical when seen on end. 



The hilum is generally very distinct. It is large and usually round, and in aggregates may be 

 double, triple, or multiple, according to the number of components. It is generally somewhat 

 eccentric and located in or slightly to one side of the median line, and has the appearance of a cavity. 

 It may be fissured, and the fissuration may be ragged, or be in the form simply of a transverse 

 curved line, or be 3-armed. Lines or fissures indicating the location of union of components of 

 aggregates are common. 



The lamellce are usually fairly distinct; they are coarse, regular, continuous rings and may be 

 distorted near the margin, which as a rule they tend to follow. In some aggregates the lamellae 

 near the hilum show the outlines of pressure facets, these parts seeming to have been covered with 



