730 STARCHES OF IRIDACE^. 



Effects of Various Reagents. With chloral hydrate-iodine reaction begins in 45 seconds in many 

 of the smaller grains and it is general in 2 minutes. About four-fifths of the entire number of grains 

 are darkened and apparently completely gelatinized in 10 minutes. The reaction is complete in 

 all the grains in 22 minutes. The hilum may or may not become distinct, and the lamellae are 

 entirely obscured. The grains are colored a deep violet. The margin usually becomes very dark 

 at all points and the reaction spreads inward over all, the violet color deepening first. There is no 

 sharp line of demarcation between the gelatinized and non-gelatinized portions. The grains swell 

 somewhat after they are completely darkened. The gelatinized grains are not large; they retain 

 much of the original form of the grain and they are of a uniform dark color. 



There is a general reaction with chromic acid in 30 seconds, and it is over in 15 minutes. The 

 hilum at first is not very distinct, but later becomes distinct. The lamella;, as a rule, are invisible. 

 The hilum swells somewhat, and the grain becomes divided by fine, radial strife which grow wider 

 and coarser as the hilum enlarges. The interior of the grain is converted rapidly. The more re- 

 sistant starch at the margin, at first, forms one thick band which is finely striated. Later, as the 

 grain continues to swell, this band is divided into two parts, the outer being rather thin and homo- 

 geneous and somewhat folded and wrinkled, while the inner part is thicker and shows fine striae 

 and a ragged inner edge. As the reaction proceeds the space separating the two parts increases, 

 especially at the distal end. The proximal end of the outer layer is dissolved, and the inner layer 

 with its gelatinous contents is extruded partly or completely through the opening. The proximal 

 end of this inner ring is now dissolved, and the gelatinous material within flows out and undergoes 

 complete solution. The two rings dissolve later. 



With pyrogallic acid there is a slight reaction in some grains in IJ^ minutes and a very slight 

 general reaction in 10 minutes. One or two are completely gelatinized in 25 minutes. There is 

 no further change after an hour. About the edges of the cover-slip the reaction is rapid and com- 

 plete. The hilum is prominent. The lamellae may be distinguished. The hilum swells somewhat, 

 and radial striae appear throughout the grain. The inner portion is altered into a gelatinous mass. 

 The marginal part forms a ring which exhibits fine striae. This ring gradually becomes smaller 

 and more homogeneous, but is never quite reduced to the film which forms the margin of a completely 

 gelatinized grain. The gelatinized grains are not very large, not folded, WTinkled, or sacculated, 

 and they retain much of the original form of the grain. 



Most grains begin to react in 21^ minutes with ferric chloride, and all show some reaction in 

 7 minutes. The reaction is over in 45 minutes, although the grains are only partially gelatinized. 

 The hilum, which at first is obscure, becomes distinct as it begins to enlarge. The grain is divided 

 by fine radial striae. The inner part is changed into a gelatinous mass. The marginal part forms a 

 finely striated ring, which grows thinner and quite homogeneous, but never becomes the thin, 

 transparent capsule of a completely gelatinized grain. The grains are fairly large, rounded, and 

 smooth, and occasionally one is seen which shows sacculations or other irregularities at the base. 



With Purdy's solution some grains show a reaction in 30 seconds. A few begin to react in 5 

 minutes. The reaction is general in 12 minutes. About half are completely gelatinized in 45 minutes 

 and about four-fifths in 1 hour and 45 minutes. The lamellae and hilum are both distinct. The 

 hilum swells, fine striae appear radiating throughout the grain, and the reaction proceeds by the 

 breaking down of the inner portion into a gelatinous mass and the formation of the marginal por- 

 tion into a finely striated ring, which becomes gradually very thin and transparent. The gelatin- 

 ized grains are fairly large, usually rounded and smooth, and retain much of the original form. 



STARCH OF TRITONIA SECURIGERA. (Plate 72, figs. 427 and 428. Chart 282.) 



Histological Characteristics. In form the grains are mostly or solely simple, and are isolatetl, 

 with the exception of a few aggregates (or compounds) in the form of doublets and triplets. Some 

 doublets consist of components varying from equal to very unequal size, tmd a few of them consist 

 of a large grain witli what appears to Ise a small grain partially embedded. There are some grains 

 with pressure facets, and in some of them the facets are hexagonal, of a honeycomb appearance. 

 The surface of the grains is rounded and tends to be regular in outline. The most common, con- 

 spicuous forms of isolated grains are spherical to ovoid, chiefly the former. There are also rounded 

 ovoid^to ellipsoidal, pyriform, sugar-loaf, and hemispherical. Among the aggregates the doublets 

 range from ovoid to oval and elliptical. The grains are not flattened and appear to be as thick as 

 broad. The spherical forms are more conspicuous with fewer aggregates than in the case of T. crocata. 



