452 



STARCHES OF AROIDE^E. 



CI PA CA 

 PC PS 



hilum begins to swell. The rest of the process is practically the same as that noted in the other Rich- 

 ardia starches. Fine stria^ appear radiating from the hilum. The hilum swells, opening out in stellate 

 form, and the ungelatinizcd portions are pushed peripherally to form a ring composed of but one 

 layer, which ring grows thinner and clearer and dissolves at one point, opening out and allowing the 

 gelatinized contents to flow out and dissolve. The rest of the ring or capsule disappears later. 



With pyrogallic acid the reaction begins in a few grains in 10 minutes. After an hour about 

 half of the grains are affected, but very few are fully gelatinized. The hilum becomes prominent, 

 but the lamellfe remain invisible; fine stride appear on the grain, and the hilum swells. The ungelatin- 

 ized portions are pushed peripherally where they form two layers, an inner granular and an outer 

 finely striated, which become thinner and clearer, but in almost every case remain divided. The 

 gelatinized grains are not very large, and the capsules are distorted, folded, or crumpled. The 

 grains outside the cover-slip react more completely, indicating a favorable influence of oxj'gen. 



The reaction with ferric chloride licgins in 2J^ minutes and is over in 40 minutes. The hilum 

 appears as a dark spot, and more prominent. It may now swell, causing a movement of the ungel- 

 atinizcd portions of the grain peripherally. Or, as the hilum swells, the grain may be divided into 

 a mmilier of entirely separate portions which swell independently. The gelatinized grains formed 

 by the latter method are large, irregular, and distorted. All are difficult to see in the surrounding 

 medium. 



With Purdy's solution there were only slight evidences of any reaction after an hour. One 

 or two grains showed fine stria; radiating from the hilum, one grain was completely gelatinized, 

 and one divided by a longitudinal fissure into unequal parts. No other changes were noted. 



STARCH OF RICHARDIA ALBO-MACULATA. (Plate 16, fig.s. 95 and 96. Chart 83.) 



Histological Characteristics. In form the grains are simple and are isolated, except a few in 

 aggregates; nearly all have pressure facets, but usually not the large number exhibited by R. elli- 

 otiana and R. africana. The consjjicuous forms are 

 polygonal; some dome-shaped, hemispherical, triangular, 

 ovoicl, and spherical grains. The grains, as in the other 

 Richardia starches, vary somewhat in form according to 

 the aspect from which they are seen. 



The Mlum is usually invisible, but is a small, round, 

 non-refractive spot, ccntrically or slightly eccentrically 

 placed; it was never found fissured, and no multiple hila 

 were seen. 



The lamellw are almost always invisible. In a few 

 grains they appeared as regular, concentric rings, with no 

 tendency to follow the faceted outlines of the margin. 

 They are coarse, and one near the hilum is apt to be 

 especially distinct. Not many appear on a grain. 



The grains vary in size from 1 to 16;n. The com- 

 mon size is about 8;u. 



Polariscopic Properties. The figiire is as a rule dis- 

 tinct, centric or slightly eccentric, in the form of a cross; 

 its lines are about the same size and distinct throughout 

 their length, not usually bent or distorted in any way. 



The degree of j)olarization is fair, probably less than that of the grains of R. elliotiana. 



With selenite the quadrants are very well defined and commonly of about the same size and 

 shape. The colors are not quite pure. 



Iodine Reactions. W\i\\ 0.25 per cent Lugol's solution the grains color very deep blue-violet, 

 deeper than R. elliotiana; with 0.12.5 per cent solution they tint readily and the color deepens rapidly, 

 but not so deeply as R. elliotiana. The color is more of a red-violet than the color of R. eUiotiana, 

 but not so reddish as the color of R. africana. After heating until all are entirely gelatinized, the 

 solution colors slightly and some of the grains color deeply and others lightly on the addition of 

 the iodine. Those coloring lightly show a pinkish-violet capsule on the addition of slight excess 

 of iodine. After lioiling for 2 minutes, many gelatinized grains have lost all of their blue-reacting 

 starch and the capsule is reduced to fragments or to amorphous granular masses. On the addition 



Curve of Reaction- Intensities of Starch of Richardia 

 albo-maculata. 



