456 STARCHES OF AROIDE^. 



The degree of polarization is fairly high, varying according to the aspect of the grain, being 

 higher if the grain is viewed from the end or edge, and it varies in different grains. 



With selenite the quadrants are well defined, but irregular in shape and size. The colors are 

 fairly pure. 



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

 with 0.125 per cent solution they color lightly. After heating until all the grains are completely 

 gelatinized, the solution is colored slightly, but the gelatinized grains deeply, with iodine. The 

 grains are swollen and somewhat distorted, but retain much of their original shape. After boiling 

 2 minutes, the solution is colored deeply, some of the grain-residues slightly and others not at all. 

 The capsules are colored a red-violet. 



Staining Reactions. With gentian violet the grains begin to stain at once, some more deeply 

 than others. The distal end of the grain stains more quickly and more deeply than the rest of the 

 grain. At the end of 30 minutes the color is deep. 



With safranin the grains begin to stain immediately, one as deeply as another. The distal 

 end of the grain stains first and most deeply. After 30 minutes the grains are deeply stained. 



Temperature Reaction. The temperature of gelatinization is 68 to 70 C, mean 69. 



Effects of Various Reagents. With chloral hydrate-iodine most grains show the beginning of 

 gelatinization in a minute. About half are gelatinized in 10 minutes and all in 30 minutes. The 

 hilum becomes very distinct as a round dark spot or bubble. The lamellae can be seen, but are 

 not especially distinct. The periphery darkens at the proximal end, or less commonly at the hilum, 

 and protrusion begins, the grain swelling more in the direction of its longitudinal than transverse 

 axis. Both ends may begin to protrude simultaneously, or more frequently swelling may at first 

 be entirely at the end. In the T and boot shapes swelling may occur from three points, all converging 

 towards the center of the grain, which is affected last. Sometimes small processes will protrude 

 at irregular points of the margin. The gelatinized grains are much elongated and somewhat broad- 

 ened. Owing to the darkly colored starch being marked l)y light, transverse fissures, the grains 

 have an appearance suggestive of annelid worms (Plate 19, figs. 113 and 114). The proximal end 

 of the swollen grain is rounded and smooth, and incloses a large, light area representing the swollen 

 hilum. The distal end is either squared or nodular, according to whether protrusion occurred from 

 all points at once or succcssivelj'. The grains retain to a great extent their original forms. 



With chromic acid the grains begin to react in 15 seconds and all are dissolved in 3^ minutes. 

 The hilum becomes more distinct, but not the lamellfe. A refractive line extends on each side of 

 the hilum, marking off the inner portion of the grain from the margin and reaching the squared 

 corners at the distal end of tlie grain. This end ojiens out fan-wise while becoming gelatinized and 

 longitudinal fissures extend ujiward into the inner portion, which separates by transverse fissures 

 and alters into coarse granules arranged in a somewhat lamellated fashion. The margin grows very 

 distinct and consists of three or four well-marked striated bands, alternately light and dark. If 

 there are two sets of lamellae, one is sejjarated from the other, the marginal portion of the grain 

 including both sets. In the meanwhile the hilum swells, the distal end of the grain is dissolved, 

 and the gelatinous inner portion gradually flows out and is dissolved, leaving the refractory mar- 

 ginal portion which dissolves last. At times the central part SAvells, and the margin on each side 

 dissolves, the two ends dissolving later, the margin of the proximal end being the last of all to 

 disappear. 



The reaction with pyrogallic acid begins in some grains in 30 seconds and all are gelatinized in 5 

 minutes. The hilum becomes more distinct, but the lamellar for the most part only slightly so. Two 

 refractive lines radiate from the hilum to the squared corners at the distal end, outlining an inner 

 space in which the lamellae are very distinct. Coarse longitudinal striae now extend from the distal 

 end, which swells out fan-wise, and some transverse fissures are formed which divide the inner 

 portion into coarse granules, arranged in lamellated fashion. The margin at the same time becomes 

 more prominent and is marked by indistinct, alternate refractive and non-refractive bands having 

 distinct fine striae. Then the hilum begins to swell rapidly and the grain as a whole swells in all 

 directions. The coarse granules in the interior dissolve very rapidly and the margin clears slowly 

 until a gelatinized grain is formed which is very large and clear antl with one end very much crumjiled 

 and notlular. A mass of granular starch persists at this end after other parts have cleared. The 

 proximal end is smooth and rounded, inclosing a clear space. The gelatinized grain retains little 

 of the original form of the grain. 



