754 STARCHES OF IRIDACBJB. 



what swollen. There is always a sharp line of demarcation between the gelatinized and non-gelat- 

 inized portions. Often there is a cap at the distal end which gelatinizes before the rest of the grain 

 is affected. In some grains the reaction begins at the distal end and at the same time at the pro- 

 jections at either extremity at the proximal end, and from these points inward over the whole grain. 

 The gelatinized grains are fairly large and of a uniform dark color, and retain some of the original 

 form. 



The reaction with chromic acid begins in 30 seconds and is over in 5J^ minutes. The reaction 

 begins with the appearance of coarse stria throughout the grain. The starch from the hilum to 

 the distal margin is converted into a granular, gelatinous mass inclosed in a thin capsule, and the 

 grain swells, leaving a narrow, striated line of resistant starch along the proximal margin. The thin 

 capsule is now dissolved at the sides, or at the distal end, and the gelatinized starch flows out and is 

 dissolved. The resistant starch at the proximal end dissolves at the same time, but not so rapidly 

 as the rest of the grain. 



With pyrogdUic acid the reaction begins in 45 seconds and is over in 33^ minutes. The reac- 

 tion begins with the appearance of fine strise throughout, followed by a swelling of the grain caused 

 by conversion of the entire grain-substance between the hilum and the sides and distal margin 

 into a finely granular, gelatinous mass. The granules disappear, leaving a small, thin, finely striated 

 line of resistant starch at the proximal end, which, after the rest of the grain is completely gelatinized, 

 becomes thinner and transparent. The gelatinized grains are large and are thrown into lamella- 

 like folds between the proximal and the distal ends, and retain much of the original form of the grain. 



The reaction with/erric chloride begins in some grains in 2J^ minutes. About half are completely 

 gelatinized in 12 minutes, four-fifths in 20 minutes, and all in 45 minutes. The grain becomes in- 

 vaded by fissures at the distal end, at the sides, and at the projections at the proximal end, from 

 which fissures, gelatinized starch oozes, forcing out the capsular covering. The process spreads 

 over nearby portions of the margin, and then slowly inward over the rest of the grain, the proximal 

 end being the last to be affected. The swollen grains are large, very much wrinkled, folded, and 

 sacculated, and retain some of the original form of the grain. 



The reaction with Purdy's solution begins in a few grains in 4 minutes. In 45 minutes half of 

 the grains are partially and a few nearly completely gelatinized. The reaction appears the same 

 quahtatively as that to pyrogallic acid. 



GENUS GELASINE. 



Gelasine is a genus of South American bulbous plants which includes only 2 species. G. azurea, 

 the only representative available as a source of starch, is a native of Argentina and is to a limited 

 extent in garden cultivation. 



STARCH OF GELASINE AZUREA. (Plate 76, figs. 453 and 454. Chart 296.) 



Histological Characteristics. — Inform the grains are simple with the exception of rare compounds 

 which consist of two components. The simple grains are isolated and there are no pressure facets. 

 There are a few clumps. The surface is, as a rule, well rounded and smooth, but there is slight 

 irregularity of outline owing to unequal development of the marginal portions. The conspicuous 

 forms are the reniform and elliptical to ovoid; also spherical, hemispherical, lenticular, triangular, 

 etc. The part of the margin corresponding to the concavity of the reniform shapes may be straight 

 or curved outward, and is not infrequently marked by a small protuberance. This part is the 

 proximal end; the distal end is very convex. The grains are slightly flattened and about one-half 

 to one-third as thick as they are broad, and the longitudinal axis of the grain is in most cases in 

 the short diameter. 



The hilum is a quite distinct, small round spot, very eccentric, and usually in or near the median 

 line. The hilum is seldom fissured. There may be, rarely, 2 hila, and they may be separated by a 

 small fissure. The fissuration may be in the form of a single longitudinal or diagonal line, or 2- or 

 3-armed. In all cases it is clear-cut and not ragged. 



The lameUce are fairly distinct, comparatively coarse, regular, continuous rings. They follow 

 closely the outline of the margin and exhibit no other irregularities. They are usually more distinct 

 near the hilum than near the margin. There are from 14 to 18 on the larger grains. 



The grains vary in size from 3 to 36/x. The common size is 24>i 



