GENUS DIEFFENBACHIA. 



457 



The reaction with ferric chloride begins in 2 minutes. Some of the grains are gelatinized in 5 

 minutes and all in 20 minutes. The hilum becomes distinct as a dark spot or bubble. The lamellae 

 are not more distinct than usual. The margin becomes clearer, causing the inner portion to appear 

 lighter and more opaque. The distal end begins to react with much irregular protrusion. Two 

 refractive lines extend obliquely toward the distal end from the hilum, the hilum swells, and the 

 rest of the grain becomes granular by the projection from the margin of irregular inter-crossing 

 fissures. These changes are followed by general swelling of the grain and the disappearance of the 

 granules. At times, and not uncommonly, the grain swells, beginning at the distal end, the hilum 

 being the last to swell. If there are T or boot shapes, or modifications of these, swelling may 

 begin at the distal end of the secondary deposits, then at the distal end of the primary part, and 

 proceed towards the hilum from these two points. The gelatinized grains thus formed are much 

 swollen and irregular in outline, often with three or four lobular projections on each side. The 

 proximal end is usually smooth and rounded, not preserving much of the original form of the grain. 



With Pvrdy's solution some grains show signs of swelling in a minute and the reaction is over in 

 45 minutes. All the grains are partially but none fully gelatinized. The hilum and lamellse become 

 very distinct and the grain is divided by many longitudinal and three or foiu* transverse fissures 

 which break up the imier portion into coarse granules arranged linearly. The distal end spreads 

 out somewhat and the grain swells in the center, causing the lines of granules to break up until 

 finally they become merely a fine, irregular granular mass. This process progressed to the hilum, 

 which finally swells. The margin in some cases is separated from this inner portion by the extension 

 of refractive lines from the hilum and is finely striated and sometimes banded. It can always be 

 differentiated at the proximal end of the grain, especially immediately after the hilum has become 

 swollen. The gelatinized grains thus formed are large and somewhat oval and retain but little of the 

 original form. A granular mass may persist at the distal end. The proximal end is rounded and clear. 



PS CI PA I 

 ~ PC PS 



STARCH OF CORTEX OF DIEFFENBACHIA SEGUINE VAR. NOBILIS. 

 (Plate 17, figs. 99 and 100. Chart 85.) 



Histological Characteristics. — In form the grains are both simple and compound, and isolated. 

 There are no aggregates. The conspicuous forms are in general like those found in the pith, but nar- 

 rower, with a much greater tendency to the cylindrical, and very few of the T-shaped, boot-shaped, 

 and allied forms. The general differences between these 

 grains and those of the pith are quite striking. The grains 

 when seen on end appear to be spherical in form, and 

 when on edge somewhat elliptical. 



The hilum is a fairly distinct, small, round spot, eccen- 

 tric one-sixth to one-eighth of the longitudinal axis, and in 

 or near the median line. It is never fissured, and there 

 are no multiple hila detectable even when secondary 

 deposits exist. 



The lamellae are distinct, comparatively fine, regular 

 or irregular segments of ellipses or circles, etc., usually 

 squared at their distal ends, varying but slightly in size 

 and distinctness in different grains, and not so fine, but 

 more distinct, near the distal end of the grains than near 

 the hilum. There are about 35 to 40 on the larger grains. 



The grains vary in size from 4 to 49/i. The common 

 size is 24fi. 



Polariscojric Properties. — The figure is usually dis- 

 tinct and generally clear-cut. The lines may be regular, 

 but are often much bent and otherwise distorted. 



The degree of polarization is fair, not varying much in different grains. It is high when the 

 grains are viewed on end. It is lower than in the pith starch of this plant. 



With selenite the quadrants are well defined and usually irregular in shape and unequal in size. 

 The colors are not pure. 



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

 with 0.125 per cent solution they color lightly and the color deepens quite readily. It is of the same 



Curve of Reaction-IntenBities of Starch of Dieffenbachia 

 seguine var. nobilis (cortex). 



