732 



STARCHES OF IRIDACBiB. 



of the inner layer also is dissolved, the inclosed gelatinized starch flows out and is dissolved, and 

 then the outer and inner rings slowly dissolve. 



Reaction with ■pyrogallic acid occurs immediately in a few grains, probably the injured ones; 

 it becomes general in 7 minutes, although it is very slight. In 17 minutes about one-sixth are fully 

 or partially gelatinized, but in 45 minutes there is not much further change. The hilum is very 

 prominent. Some of the lamellae may be distinguished. The hilum swells and fine strise appear 

 radiating throughout the grain. The inner portion becomes gelatinous and the more resistant 

 starch at the margin forms a ring, which is at first thick and finely striated, but later becomes thin 

 and homogeneous until it forms merely the transparent wall of a gelatinous grain. The gelatinized 

 grains are fairly large, rounded in outline, and not much crumpled or folded. They retain much 

 of the original form of the grain. 



A few grains react at once with ferric chloride and some of the smaller, intact grains in 1 3^ to 2 

 minutes. The reaction is general in 5 minutes. All are partially gelatinized in 13 minutes, and the 

 reaction is complete in 36 minutes. The hilum becomes distinct, but the lamellae are obscure. The 

 hilum swells, and the grain becomes divided by fine striae. As the hilum continues to enlarge and the 

 central part of the grain becomes gelatinous, the more resistant marginal starch forms a radially stri- 

 ated ring, which becomes thinner and clearer as the grain continues to swell, until finally it is a thin, 

 homogeneous envelope inclosing transparent, gelatinized starch, The gelatinized grains are fairly large, 

 but not much wrinkled, folded, or sacculated. They retain much of the original form of the grain. 



A niunber of grains react at once with Purdy's solution. The reaction is general in 2 minutes, and 

 about one-third are partially or completely gelatinized in 8 minutes. In 30 minutes about half are 

 gelatinized and in 80 minutes about four-fifths are completely gelatinized. The hilum and lamellae 

 are both very distinct. The hilum swells. The grain becomes divided by fine striae. The inner part 

 becomes gelatinous, and the outer part of more resistant starch forms a band which shows striae and 

 three or four alternate refractive and non-refractive concentric rings. This band becomes thinner and 

 clearer as the grain continues to swell, until it is reduced to a thin wall. The gelatinized grains are 

 not very large; some are folded and distorted, but most of them retain much of the original form. 



STARCH OF TRITONIA POTTSII. (Plate 72, figs. 429 and 430. Chart 283.) 



Histological Characteristics. — In form the grains are simple and isolated. Many are marked 

 with one, two, or rarely more well or poorly defined pressure facets at the distal end. There are 

 some clumps. The surface of the grains is rounded and tends to be quite regular. The conspicuous 

 forms are the hemispherical, ovoid, rounded ovoid, and 

 spherical; also triangular and other polygonal forms arise 

 through peculiarities of the pressiu-e facets. The ovoid 

 and spherical grains are not flattened and when on end 

 appear to be spherical. The preparation was not very 

 clean, more or less foreign matter being adherent to the 

 grains. The general appearance of these grains differs 

 appreciably from that of T. crocata and T. securigera, 

 but resembles closely that of T. crocosmmflora. 



The hilum is a fairly distinct, small round spot, usu- 

 ally eccentric about two-fifths to one-third of the longi- 

 tudinal axis, and in the median line. Rarely it is centric. 

 It is often fissxu'ed, and the fissures may be shallow 

 or deep, short or long. There is usually either a single, 

 straight, transverse or diagonally placed fissure, or three 

 fissures of varying length, generally placed in the diagonal 

 axes of the grain, and there is rarely a small, irregularly 

 stellate arrangement of fissures. There are occasionally 

 2 hila in one grain. 



The lamellce are not as a rule distinct and are rather 

 coarse, regular continuous rings which usually follow the outline of the margin of the grain. They 

 are larger and more distinct near the hilum than near the margin and do not vary much in different 

 grains. There are usually 10 to 12 on the larger grains. 



The grains vary in size from 3 to 32/i. The common size is 20/*. 



Curve of Reaction- In tens! tiea of Starch of Tritonia pottsii. 



