700 



STARCHES OF IRIDACEiE. 



MINUTES 



Curve of Reaction-Intensities of Starch of Iris reticulata. 



Polariscopic Properties. — The figure is generally eccentric and distinct. The lines of the figure 

 are rather thick and often straight, with slight broadening at the margin of the grain; sometimes 

 bisected. The figure is fairly clear-cut, and more distinct and regular than in I. florentina. 



The degree of polarization is high to very high, sometimes varying in one aspect of the same 

 grain. It is markedly higher than in I. florentina. 



With selenite the quadrants are usually irregular in shape and size. The colors are generally 

 pure, purer than in /. florentina, but the yellow is occasionally not quite pure. 



Iodine Reactions. — With 0.25 per cent Lugol's solution the grains all begin to color a deep 

 violet-blue; with 0.125 per cent solution they color fairly and the color deepens fairly rapidly. It 

 is more than that of the grains of /. florentina. After 

 heating in water until the grains are completely gelatin- 

 ized, the solution and the gelatinized grains color deeply 

 on the addition of iodine. After boiling for 2 minutes 

 the solution colors very deeply, but most of the grain- 

 residues not at all. The capsules all color reddish-violet 

 with an excess of iodine. 



Staining Reactions. — ^With gentian violet and with 

 safranin the grains all begin to stain at once and in 30 

 minutes they are fairly stained, distinctly more than the 

 grains of /. florentina. 



Temperature Reaction. — The temperature of gelatin- 

 ization is 64.5° to 66° C, mean 65.25°. 



Effects of Various Reagents. — With chloral hydrate- 

 iodine reaction begins in a few grains in as many sec- 

 onds and in all in a minute. It is complete in two-thirds 

 of the grains in 17 minutes, in four-fifths in 25 minutes, 

 and in all in 40 minutes. It is qualitatively the same as 

 that of the grains of /. florentina. 



The reaction with chromic acid begins in most grains 

 in 15 seconds, in the rest in 30 seconds, and is over in 2 minutes. It is the same qualitatively as 

 that of the grains of /. florentina, except that in these grains a bubble usually forms at the hilum, 

 which increases and then decreases in size, accompanied by invagination at the proximal end fol- 

 lowed by the opposite movement, and then the bubble disappears. Also the outer coating may be dis- 

 solved at either the proximal or the distal end, whereas in I. florentina the solution occurs at the latter. 



The reaction with pyrogallic add begins in 15 seconds and is over in a minute. It is the same 

 qualitatively as that of the grains of /. florentina, except that a large bubble forms at the hilum of 

 every grain. 



Reaction with ferric chloride begins in some grains in 30 seconds, is complete in nearly all in 25 

 minutes, and in all in 35 minutes. It is the same qualitatively as that of the grains of I. florentina. 



Reaction with Purdy's solution begins in some grains at once and in all in 45 seconds, three- 

 fourths of the grains are nearly completely gelatinized and the others are partially gelatinized in 

 4 minutes, and all are nearly completely gelatinized in 12 minutes. The reaction is the same quali- 

 tatively as that of the grains of /. florentina. 



STARCH OF IRIS HISTRIO. (Plate 66, figs. 393 and 394. Chart 265.) 



Histological Characteristics. — In form the grains are usually simple. Compound grains, aggre- 

 gates, separated-grains which are chiefly dome-shaped or polygonal with well-marked pressure facets, 

 and a very few clumps are present. The surface is sometimes irregular. Many grains have an irregu- 

 lar undulating margin as well as the rounded protuberances and secondary deposits of lamellae 

 similar to those noted in the grains of /. florentina. The secondary sets of lamella frequently appear 

 at either side of the distal end of an oval, rounded grain. The conspicuous forms are cone-shaped 

 with rounded apex, broadly triangular with rounded angles to clam-shell and oyster-shell shapes, 

 and ovoid with squared end. Among the compound grains are found the broadly lenticular with 

 rounded ends, the irregular oval, and the knob shape noted for I. florentina. The aggregates consist 

 of a large grain with one or more small grains, although there are doublets, triplets, and even 

 multiples made up of components of equal or about equal size. The grains are broader in relation 



