GENUS ^SCULUS. 439 



After heating in water until all the grains are completely gelatinized, the solution colors fairly and 

 the gelatinized .urains dcojil^' on addition of iodine. After boiling for 2 minutes the solution colors 

 very deeply and most of the grain-residues lightly. The capsules color pinkish-violet with an 

 excess of iodine. 



Stairnng Reactions. With gentian violet the grains begin to stain at once and in 30 minutes 

 are fair to lightly stained. 



With safranin the grains begin to stain at once and in 30 minutes are lightly stained. 



Temperature Reaction. The temperature of gelatinization is 68.5 to 70 C, mean 69. 



Effects of Various Reagents. With chloral hijdrate-iodine reaction begins in the small grains 

 in 20 seconds and in the large grains in 45 seconds. All the small grains are gelatinized in a minute 

 and all the large grains in 8 minutes. The reaction begins in all the grains at the pointed distal 

 end, which grows dark but does not swell very much. Then the reaction progresses about the mar- 

 gin and over the rest of the surface into the interior. The grain does not swell very much imtil 

 the hilum is reached, at which point a bubble is usually seen to be present. The bubble increases 

 very greatly in size as the starch surrounding the hilimi darkens and swells rapidly, and then de- 

 creases and finally disappears. The gelatinized grains are fairly large and retain much of their 

 original form. They usually show a light center surrounded by a thick, dark band. 



The reaction with chromic acid begins in 15 seconds and is over in a minute. The reaction 

 begins at the distal end, which protrudes in the form of a large, thin-walled mass; then the grain 

 becomes largely covered by fine striae, which grow coarse, and the interior is broken up into coarse 

 granules, while the margin is transformed into a fairly thick band, which is striated and shows 

 remains of lamelljB. This band is discontinuous at the distal end. The granules melt down into a 

 gelatinous mass and the marginal band becomes thinner and homogeneous in appearance as the 

 whole grain swells. Then the capsule at the distal end dissolves, and the gelatinous starch in the 

 interior flows out and is dissolved, and the marginal band is dissolved later from the distal end 

 upward. 



Reaction with pyrogallic acid in some grains begins in a few seconds, in all in 30 seconds, and 

 is over in 2 minutes. It begins at the distal end, which swells greatly; then the starch about the 

 hilum becomes gelatinous, the grain is marked by fine striae, and the starch in the center of the 

 area between the hilum and the distal end is broken up into granules, while the marginal portion 

 forms a thick band, which is striated and marked by the remains of the lamellae and is discontinuous 

 at the distal end. The granules break down into a gelatinous mass, the grain swells, and the marginal 

 band becomes fairly thin and homogeneous in appearance. The gelatinized grains are large and 

 have a convoluted and twisted, thin-walled distal end and a smooth, thick-walled proximal end. 

 They retain some of their original form. 



With ferric chloride most of the smaller grains begin to react in 30 seconds, and some of the 

 larger grains in 45 seconds. The reaction is over in practically all in 5 minutes. The distal end is 

 the first to show change. It becomes gelatinous and swells out irregularly. If the grains are much 

 pointed at the proximal end this also becomes gelatinized, swells out in the same way, and then 

 the process advances from both ends to the central part, which frequently is the first part to split 

 into several pieces which gelatinize separately. In grains not pointed at the proximal end the distal 

 end is affected; then the process moves upward over the rest of the grain, and frequently before the 

 starch around the hilum and at the proximal end is gelatinized it is split into several pieces which 

 gelatinize later. The gelatinized grains are very large and much convoluted and irregular at the 

 distal end, but smooth in the rest of the grain. 



The reaction with Purdy's solution begins in most of the small grains and in some of the large 

 grains in 30 seconds. Many small grains and some medium-sized grains are gelatinized in 3 minutes, 

 and all of the small and large grains are nearly or completely gelatinized in 20 minutes. 



NOTES ON THE STARCH OF ^SCULUS HIPPOCASTANUM. 

 A relationship is commonly associated in the popular mind between the common chestnut 

 and the horse chestnut, both on account of the similarity of the names and the gross general like- 

 ness of the seeds. It will be seen by an examination of the text and photographs that the starches 

 of the seeds of these two genera are quite different. In histological characteristics the two kinds 

 of starches could not be confounded, and in the reactions the differences are diagnostic, most notice- 

 ably in the temperature of gelatinization (9 difference). 

 30 



