GENUS CYCAS. 895 



invisible. There occurs a darkening of irregular points on the margin, usually at the angles of the 

 facets at the base, but sometimes on the rounded sides. These points protrude and from them the 

 process extends all over the grain, causing a general swelling. The margin is usually affected before 

 the central portion and in some grains it is the only part involved, in which case the grains have a 

 blue, gelatinous ring in the form of many irregular, saccular projections surrounding a violet-colored, 

 non-gelatinized, central mass. The gelatinized grains are not very large nor much distorted. The 

 reaction affects a larger proportion of grains than in the starch of C. revoluta. 



The reaction with chromic add begins in 45 seconds and is over in 3J^ minutes. The hilum 

 becomes prominent, also the lamellae. Fine strise appear, which radiate from the hilum throughout 

 the grain. The hilum swells and the marginal, ungelatinized portion of the grains forms a thick band, 

 finely striated but not showing refractive and non-refractive rings. This band becomes dissolved 

 at a given point, usually the angle of one of the facets, and the granular, gelatinous, semi-liquid 

 starch inside flows out and is dissolved. The remainder of the band rapidly passes into solution. 



Reaction with pyrogallic add begins slightly m. \]/z minutes and all the grains are completely 

 gelatinized in 25 minutes. There appeared to be more reaction in grains outside the cover-slip 

 than beneath it. The hilum and lamellae are rendered more distinct. Some grains are invaded at 

 the base by fissures, which extend from the margin and become gelatinized at these points, the 

 rest of the grain meanwhile becoming covered by fine radial striae. The hilum swells and a band 

 of gelatinized starch forms at the margin, which band is finely striated, but not distinctly marked 

 by alternate refractive and non-refractive rings. This part of the grain is transformed gradually 

 to a thin, homogeneous, enveloping substance. The gelatinized grains thus formed are large and 

 also somewhat distorted and folded if there has been any independent swelling at the base. As a 

 rule, they retain much of the original shape of the grain. 



With ferric chloride the reaction begins in some grains in a minute and is completed in 25 minutes. 

 The hilum becomes prominent as a dark spot or bubble. The margin of the grains becomes clearer 

 and darker, while the inner portion, which is very small, appears by contrast to be more opaque 

 but lighter. A very rapid gelatinization of the more soluble portions of the grain occurs and then 

 of the less soluble portions, the latter being located at the margin. Gelatinization is attended by 

 great swelling; in some grains there is at first great swelling and protrusion from the angles of the 

 facets, followed by gelatinization of the grain as a whole. The gelatinized grains are very large 

 and ovoid in shape, and do not retain any of the original shape, but they are not much folded, 

 invaginated, or crumpled. 



With Purdy's solution the reaction begins in a few grains in 3 to 4 minutes and a very few are 

 completely gelatinized in IJ^ hours, although most are unaffected. The hilum and lamellae become 

 very prominent. The reaction consists, as in C. revoluta, in the appearance of fine striae throughout 

 the grain; the swelling of the hilum; the formation of a striated, peripheral band which shows more 

 or less distinctly alternate refractive and non-refractive rings; the dissolution of this band; and the 

 formation of a large, gelatinized grain which retains some of the original form, showing few wrinkles, 

 lines, or distortions of any sort. 



Differentiation of Certain Starches of the Genus Cycas. 



HisTOLOQicAL CHARACTERISTICS. — Continued. 



Size. 

 C. revolvla: From 5 to 25m, commonly 14/b. 

 C. circiTiaHs: From 3 to 20fi, commonly 12m. 



POLABISCOPIC PbOPEHTIES. 



Figure. 

 C. revoluta: Centric or very slightly eccentric, distinct 



cross; lines straight and vary in width. 

 C. cireinalis: Same as in C. revoluta. 



Degree of Polarization. 

 C. revoluta: High. 

 C. cireinalis: High, the same as in C. revoluta. 



Polarization uiith Selenite— Quadrants and Colors. 



HiSTOLOQICAL CHARACTERISTICS. 



Conspicuous Forms. 



C. revoluta: Simple, few aggregates, pressure facets on 

 most grains. Hemispherical to dome-shaped, round 

 or nearly round and ovoid. 



C. cireinalis: The same as in C. revoluta, but with greater 

 abundance of angular forms. 



Hilum— Form, Number, and Position. 



C. revoluta: Form distinct, medium-sized, round spot 

 or cavity; sottietimes fissured, fissures not ex- 

 tensive. Position centric or very slightly eccentric. 



C. cireinalis: Form and position the same as in C. revoluta. 



Lamelke — General Characteristics and Number. 



C. revoluta: Distinct, regular, concentric, rather fine. | C. revoluta: Quadrants sharply defined, regular in shape, 



About 10 on the larger grains. 

 C. cireinalis: Same as in C. revoluta. About 8 on the 

 large grains. 



unequal in size. Colors pure. 

 C. cireinalis: Quadrants the same as in C revoluta. 

 Colors usually pure. 



