468 



STAECHEB OF AROIDEiB. 



PS CI PA CA 

 ~ PC PS 



deviation to more than 45°. There are T-shaped, boot-shaped, boomerang-shaped, and various irreg- 

 ular forms. Some of the smaller grains are irregularly oval, ovoid, or round. The elongated forms 

 are as thick as broad, and on end appear round. The T, boot, oval, and irregularly rounded 

 forms are flattened, and from the end appear oval to elliptical. Evidences of erosion are not 

 uncommon. The grains usually are not only smaller than those of the pith starch, but there is, as 

 in the cortex starch of D. seguine var. nofnlis, a distinct tendency to a cylindrical form. 



The hilum is a not very distinct, small, round, refractive spot, and not fissured. It is usually 

 in the median line and commonly at the smaller end of the grain. It is eccentric generally about 

 two-fifths of the longitudinal diameter. No multiple hila were noted. 



The lameUce are fairly distinct, fine, regular or irregular rings or ellipses or segments of rings 

 or elhpses, which, except near the hilum, tend to follow the outline of the grain. The distal ends 

 of the ellipses are usually flattened and sometimes the lamellae are wavy. They vary in size and 

 spacing in different grains and even in the same grain. 

 Those at the distal end are usually the largest. In the 

 boot-shaped, T-shaped, and related forms are two sets of 

 lamellae, those of the secondary sets being the larger and 

 more distinct. The average number of lamellae is 26. 



The grains vary in size from 5 to 50m. The common 

 size is 25/i. They are commonly from about one-third to 

 one-fourth as broad as they are long. 



Polariscopic Properties. — The figure is usually very 

 eccentric in the elongated grains, and in the round forms 

 slightly eccentric. The lines are narrower than in the 

 pith starch, ragged, and usually more or less bent or 

 wavy. In grains with secondary lamellae the figure may 

 be more or less modified in accordance with the peculiari- 

 ties of form and structure. 



The degree of polarization is fairly high. It is not 

 so high as that of the pith starch. It is, as in other 

 starches, highest when the grain is viewed from the end 

 or edge, and also varies somewhat in different grains. 



With selenite the quadrants are well defined, but very 

 irregular in shape and size. The colors are only fairly pure, even less so than in the pith starch. 



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

 with 0.125 per cent solution they color lightly. The depth of color in both reactions is less than 

 in the pith starch. After heating until all the grains are completely gelatinized the solution is 

 colored a light indigo and the grains a very deep indigo with iodine. After boiling for 2 minutes 

 the solution colors deeply, but the grain-residues lightly with iodine. With excess of iodine the 

 capsules become a reddish-violet. 



Staining Reactions. — With gentian violet the stain begins in a minute and after 30 minutes 

 the grains are deeply colored. The reaction is less than with the pith starch. 



With safranin in a minute the grains tint lightly and after 30 minutes they are fairly deeply 

 stained, not so deeply as the pith starch. 



Temperature Reaction. — The temperature of gelatinization is 69° to 71° C, mean 70°. 



Effects of Various Reagents. — With chloral hydrate-iodine the reaction begins in a minute and 

 is over in 30 minutes, about three-fourths of the grains being completely and the others partially 

 gelatinized. The reaction is qualitatively the same as that of the pith starch. 



Reaction with chromic acid begins in a minute and all the grains are dissolved in 4 minutes. 

 This reaction is qualitatively the same as that of the pith starch. 



The reaction with pyrogallic acid begins in a minute and all the grains are gelatinized in 11 

 minutes. This reaction is qualitatively the same as that of the pith starch. 



With ferric chloride reaction begins in 30 seconds to a minute and all the grains are swollen 

 in 20 minutes. This reaction is qualitatively the same as that of the pith starch. 



With Purdy's solviion the reaction begins in 1 to IJ^ minutes, but after Ij^ hours only about 

 one-fourth of the grains are gelatinized, and they only partially. This reaction is qualitatively 

 the same as that of the pith starch. 



Curve of Reaction-Intensities of Starch of 

 Dieffenbachia illustris (cortex). 



