762 



STARCHES OF IRIDACE^. 



STARCH OF IXIA VIRIDIFLORA. (Plate 77, figs. 461 and 462. Chart 299.) 



Histological Characteristics. In form the grains are simple and are isolated, except many 

 aggregates in the form of doublets, triplets, and quadruplets of equal or unequal size. Nearly all 

 the isolated grains have pressure facets, commonly from one to three, at the distal end. The sur- 

 face tends to be smooth and regular. The conspicuous forms are the hemispherical with one to 

 tliree pressure facets at the base, spherical, and spherical to ovoid. There are many grains of 

 polygonal and other forms among the smaller grains. The doublets are elliptical and the triplets 

 rounded triangular. The grains are of the same thickness as width and appear to be spherical 

 when seen on end. 



The hilum is a comparatively large, round, fairly distinct spot, usually situated slightly ec- 

 centrically and in the median line, rarely fissured. The lines of union between the components of 

 doublets and triplets are marked by depressions or fissures. 



The lamellce are fairly distinct, rather coarse, regular, continuous rings, usually the shape of 

 the margin of the gi-ain. There are 5 to 6 on the larger grains. 



The grains vary in size; the smaller are 2yu; the larger are 17 by 15/x in length and breadth. 

 The common size is 12 by 10/x in length and breadth. 



Polariscopic Properties. The figure is usually slightly eccentric, fairly distinct, and generally 

 clear-cut. One or more of its lines sometimes become 

 broadened and not clearly defined. The center may be 

 represented by a large dark area. 



The degree of polarization is fair, varying somewhat 

 in different grains and in different aspects of the same 

 grain. It is lower than that of the grains of I. speciosa. 



With selenite the quadrants are fairly well defined, 

 imequal in size, and generally regular in shape. The 

 colors are pure. 



Iodine Reactions. With 0.25 per cent Lugol's solu- 

 tion the grains color a fairly deep blue-violet; with 0.125 

 per cent solution they color rather lightly and the color 

 deepens slowly. It is not quite so deep as that of the 

 grains of /. speciosa. After heating in water until the 

 grains are completely gelatinized, the solution colors 

 lightly and the swollen grains very deeply on the addi- 

 tion of iodine. After boiling for 2 minutes the solution 

 colors deeply and the grain-residues fairly to not at all. 

 The capsule colors violet with an excess of iodine. 



Staining Reactions. With gentian violet the grains 

 begin to stain at once very lightly, and in 30 minutes are lightly stained. The color is deeper than 

 that of the grains of /. speciosa. 



With safranin the grains begin to stain at once and in 30 minutes are fairly stained. The color 

 is deeper than that of the grains of I. speciosa. 



Temperature Reaction. The temperature of gelatinization is 82 to 84 C, mean 83. 



Effects of Various Reagents. With chloral hijdrale-iodine reaction begins in some grains in 30 

 minutes, and in all in a minute. It is over in most of the grains in 6 minutes and in all in 12 min- 

 utes. It is qualitatively the same as that of the grains of /. speciosa. 



The reaction with chromic acid begins in 15 seconds and is over in 1^ minutes. It is the same 

 qualitatively as that of the grains of /. speciosa. 



The reaction with pyrogallic acid begins in 45 seconds and is over in 18 minutes. It is the same 

 qualitatively as that of the grains of /. speciosa. 



The reaction with ferric chloride begins in many grains in 45 seconds and is over in 15 minutes. 

 It is the same qualitatively as that of the grains of /. speciosa. 



Reaction with Purdy's solution begins in some grains in 3 minutes; in 10 minutes a few and in 

 30 minutes all are nearly completely gelatinized. The reaction is the same qualitatively as that of 

 the grains of /. speciosa. 



Curve of Reaction-Intensities of Starch of 

 Ixia viridiflora. 



