894 



STARCHES OF CYCADACE^. 



and non-refractive rings. This band is finally gelatinized and there is ultimately formed a large 

 gelatinous mass. In most of the reacting grains the process stops at various stages. 



STARCH OF CYCAS CIRCINALIS. (Plate 101, figs. 605 and 606. Chart 395.) 



Histological Characteristics. — In form the grains are simple. There are a few small aggregates 

 and many large clumps. Nearly all the grains show pressure facets which are very clearly defined. 

 The number of facets to a single grain is commonly one or two or three, which facets are grouped 

 at the base; but a larger niunber is not infrequent. The basic form of the grain is spherical, 

 which form becomes modified in various ways by the position, size, and number of the facets. The 

 conspicuous grains are hemispherical to dome-shaped, spherical, quadrangular and other polygonal 

 forms. The grains are on the whole much more irregular in form than in C. revoluta. Looking 

 down at the proximal end, the grains usually appear round. 



The hilum is a fairly distinct, medium-sized, round, non-refractive spot, usually not fissured; 

 rarely a small transverse and longitudinal fissure may be seen. In some cases a distinct cavity at 

 the hilum appears to communicate with the interior of the grain. The hilum is centrally or only 

 slightly eccentrically placed. No double hila were pres- 

 ent. One lenticular-shaped hilum was noted. 



The lamelUB are in the form of distinct, regular, con- 

 centric rings. Those near the hilum are much more 

 distinct than those near the margin, and one midway 

 between the hilum and the margin and one quite near 

 the margin are usually very distinct. Generally only 

 those near the margin follow the marginal outline, the 

 others being regular circular rings. They are compara- 

 tively fine and average about 8 in large grains. 



The grains vary in size from 3 to 20/*. The common 

 size is 12ju. 



Polariscopic Properties. — The figure is centric or 

 slightly eccentric and distinct. All the lines show equally 

 well and are of equal distinctness throughout their length, 

 except near the margin of the grain, where they usually be- 

 come wider and less distinct; they tend to vary in width. 

 At the facets there is often an appearance as of another 

 figure, owing probably to the depression of the surface. 



The degree of polarization is high, about the same as in C revoluta. It does not vary notably 

 in the different aspects of the same grain, but there may be low degrees of polarization at the facets, 

 probably due to a depression at this point. It varies in different grains. 



With selenite the quadrants are sharply defined, of equal size, and regular in shape. The colors 

 are usually pure. 



Iodine Reactions. — With 0.25 per cent Lugol's solution the grains are colored immediately 

 and deeply a blue-violet; with 0.125 per cent solution the grains color at once lightly and the color 

 deepens quickly. The depth of color is the same as that with C. revoluta. After heating in water 

 until the grains are all completely gelatinized, the solution and the gelatinized grains color a fairly 

 deep blue on the addition of iodine and many grains show a violet capsule on the addition of very 

 little iodine. After boiling for 2 minutes, the solution colors more deeply, but the grain-residues 

 color a very faint blue-violet. Some contain deep, blue-colored starch and all are much wrinkled, 

 crumpled, and otherwise distorted. 



Staining Reactions. — With gentian violet staining begins very lightly in 3 minutes and the grains 

 are deeply and evenly stained a dull violet in 30 minutes. The depth of color is the same as with 

 C revoluta. 



With safranin staining be^s slightly in 4 minutes and in 30 minutes the grains are colored 

 faintly and evenly, about the same as in C. revoluta. 



Temperature Reaction. — The temperature of gelatinization is 71° to 73° C, mean 72°. 



Effects of Various Reagents. — With chloral hydrate-iodine the reaction begins in some of the small 

 grains in a minute and in the larger grains in 3 or 4 minutes. In 40 minutes almost all are completely 

 swollen. The hilum is rendered prominent as a dark spot or bubble and the lamellae become 



MINUTES 

 Curve of Reaction-Intensities of Starch of Cycas circinalis. 



