766 



STAKCHES OP IRIDACE^. 



inised grains are not very large, they retain much of then- original form, and are usually of a uni- 

 form dark-blue color. 



Reaction with chromic add begins in 5 seconds and is over in IJ^ minutes. The hilum swells, 

 or appears to swell, and fine strise radiate from this point in all directions. The less resistant starch 

 is converted into a semifluid, gelatinous mass in the central portion of the grain, and the grain swells. 

 The more resistant starch forms a thick, coarsely striated, marginal band, which progressively 

 grows thin and transparent as the grain swells. One portion is dissolved, usually at one comer or 

 edge of a facet, and the semifluid mass in the interior flows out and is dissolved, and the remainder 

 of the marginal band dissolves later. 



The reaction with pyrogalUc add begins in 30 seconds and is over in 20 minutes. The hilum 

 appears to enlarge, and fine but distinct striae radiate from the hilum in all directions. The less 

 resistant starch is transformed into a semifluid mass in the interior of the grain, and the more 

 resistant starch forms a thick, finely striated, marginal band, which as the grain swells grows clearer 

 and somewhat thinner and transparent. The gelatinized grains are large, not very much distorted, 

 and retain much of their original form. 



With ferric chloride the reaction begins in many grains in 45 seconds and is over in 15 minutes. 

 It begins at the distal end, where the corners and edges of the facets become gelatinous and swell 

 out irregularly. Sometimes this process is followed by gelatinization and swelling of the marginal 

 part of the proximal end. The process now spreads over the rest of the grain, and when the hilum is 

 reached the whole grain swells greatly. The swollen grains are large, greatly folded and sacculated, 

 and do not retain much of the original form of the grain. 



The reaction with Purdy's solution begins in many grains in 15 seconds, and in all in 40 seconds. 

 It is over in about two-thirds of the total number, including most of the smaller grains, in 4 min- 

 utes. It is qualitatively the same as that to pyrogallic acid. 



STAKCH OF BABIANA VAR. (ATHRACTION). (Plate 78, figs. 467 and 468. Chart 302.) 



Histological Characteristics. — In form the grains are simple. They are isolated, with the excep- 

 tion of a few aggregates, usually in the form of doublets and triplets. The isolated grains have from 

 one to four pressure facets at the distal end. The surface of the grains is smooth and quite regular. 

 The conspicuous forms are the hemispherical with usually 

 one to three pressure facets at the base, and spherical ; also 

 ovoid to oval and elliptical, and some polygonal forms. 

 The doublets range from elliptical to oval, and the triplets 

 are usually roimded triangular. The grains are not flat- 

 tened and appear to be spherical when seen on end. 



The hilum is a fairly distinct and usually a compara- 

 tively large round spot, commonly slightly eccentric; oc- 

 casionally marked by a small round cavity and rarely 

 sUghtly fissured. Two or more hila are rarely observed 

 on an isolated grain. In some grains there are two lines 

 extending from each side of the cavity or cleft to the 

 angles made at the facets. 



Lamellce indistinct and, when seen, appear regular, 

 rather coarse, and continuous. Number not determined. 



The grains vary in size; the smaller are 2 by 2/i; the 

 larger are 19 by 14/t and 14 by 18;* in length and breadth. 

 The common size is about 12/i. 



Polariscopic Properties. — ^The^wre is usually slightly 

 eccentric, distinct, clear-cut, and regular; its lines are generally straight and clearly defined. 



The degree of polarization is low to fairly high, usually fair. It varies in different grains and 

 in different aspects of a grain. It is lower than in B. var. (Violacea). 



With selenite the quadrants are usually well defined, fairly regular in shape, and commonly 

 unequal in size. The colors are, as a rule, pure. 



Iodine Reactions. — With 0.25 per cent Lugol's solution the grains color a rather light blue-violet 

 and the color deepens rapidly; with 0.125 per cent solution the grains color lightly and the color 

 deepens fably rapidly. It is less than that of the grains of B. var. (Violacea). After heating in 



Chart No. 302. 



PS CI PA CA 

 "~ POPS 



MINUTES 



Curve of Reaction-Intensities of Starch of 

 Babiana var. (Athraction). 



