GENUS CANNA. 



797 



Polariscopic Properties The figure is very distinct and generally clear-cut. Its lines are rather 

 broad, becoming slightly broader and less clear-cut near the margin. Usually two lines are for the 

 most part visible and cross the grain diagonally; sometimes there are only one and small parts of 

 others, in which case the single line corresponds with the longitudinal axis of the grain. The lines 

 are usually regular, but placed at varying angles to one another. 



The degree of polarization is very high; when seen on edge or end it is higher than in other 

 aspects and does not vary materially in different grains or in different parts of the same aspect of a 

 given grain. Polarization colors appear in most grains. 



With selenite the quadrants are fairly well defined, fairly regular in form, and unequal in size. 

 The colors are usually pure. 



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

 violet, the marginal part being more deeply colored than the rest of the grain; with 0.125 per 

 cent solution the grains color readily, but the tint deepens rapidly. After heating in water until all 

 the grains are completely gelatinized, the solution becomes a deep indigo color and the grains a 

 very light indigo upon the addition of iodine. After boil- 

 ing for 2 minutes the solution colors even more deeply 

 and the grain-residues light or not at all. The capsules 

 all color a red-violet with a slight excess of iodine. 



Staining Reactions. With gentian violet the grains 

 begin to stain at once. After 30 minutes they are deeply 

 stained, some more than others, and the margins more 

 than the inner portion. 



With safranin the grains begin to stain deeply at 

 once. After 30 minutes they are very deeply stained. 

 This coloration is more intense than with gentian violet. 



Temperature Reaction. The temperature of gelatini- 

 zation is 68 to 70 C, mean 69. 



Effects of Various Reagents. With chloral hydrate- 

 iodin some grains begin to react in a minute and all are 

 darkened in 25 minutes. The hilum and lamellae become 

 indistinct. The prominent points on the margin grow 

 dark and begin to protrude and the reaction extends along 

 the margin from one point to another. The protrusion 

 from the margin may surround the grain entirely, inclos- 

 ing a central, unswoUen portion which swells later. In some grains the hilum and one or two 

 adjacent points may swell out first, then the distal end, and finally the central portion. After the 

 whole grain is darkened, swelling continues for some time. The resulting gelatinized grains are 

 fairly large, the proximal portion is lobular, and the distal rounded. The part between the hilum 

 and the distal margin shows a number of irregular concentric bands of darkened starch, which are 

 partially or completely separated by light fissures. (See plate 86, figs. 511 to 516.) 



With chromic acid the reaction begins in 30 seconds, and is over in 2 minutes. The hilum and 

 lamelliB become more distinct. The hilum swells, and fine striae appear which radiate from the 

 hilum throughout the grain. Fissures take the place of the most prominent of these striae and ex- 

 tend deeply throughout the grain. The upper margin of the proximal end of the grain is dissolved, 

 then the rest of the grain swells and dissolves in a very typical manner. The fine striae which have 

 obscured the lamellae disappear from a crescentic zone at the distal end and the lamellae reappear, 

 and then the zone separated from the rest of the grain is dissolved; another such zone forms and 

 separates, and then a third is formed, but this rarely separates. The rest of the grain, which con- 

 sists of rows of large granules, becomes clearer and more transparent and finally dissolves also. 

 (See plate 87, figs. 519 to 522.) 



With pyrogallic acid the grains begin to react in a minute and about one-sixth of the total 

 number are gelatinized in 20 minutes, the rest being in all stages of the reaction, from a slight swell- 

 ing of the hilum to partial gelatinization. There is no further change. The hilum swells slightly, 

 and fine striae appear which radiate from the hilum through the grain, 4 or 5 of which develop into 

 very deep fissures which split the grain into pyramids with bases on the distal margin and apexes 

 directed towards the hilum. As the grain continues to swell these parts are repeatedly subdivided 



Curve of Reaction-Intensities of Starch of Canna 

 warszewiczii. 



