GENUS BATATAS. SSf) 



Iodine Rcaclions. With 0.25 per cent Lugol's solution the grains are colored immediately 

 and very deeply a blue-violet; with 0.125 per cent solution th(> grains immctliately color lightly 

 and the color deepens quickly. After heating in water until all the grains are completely gelatin- 

 ized, the solution is colored lightly and the grains deeply on the addition of iodine. Some grains 

 have the violet-colored capsule. After boiling for 2 minutes, the solution is colored much more 

 deeply, the grain-residues but little or not at all. All of the capsules are colored violet by using 

 very little iodine. A few grains arc completely disintegrated. 



Staining RcncUons. With gentian violet staining begins immediately and aft(ir 30 minutes 

 the grains arc colored fairly well. 



With safranin the grains begin to stain immediately and after 30 minutes they are stained a 

 }-ello wish-red, which is not very deep. 



Tempcmturc Reaction. The temperature of gelatinization is 73" to 75" C, mean 74". 



Effects of Varioiis Reagents. With chloral hydrate-iodine reaction begins in 30 seconds. Al- 

 most all are blue in 7 minutes and after an hour all are completely gelatinized. The hilum becomes 

 prominent, but the lamelkc are usually invisible. The margin becomes clearer and darker; and the 

 edges and corners of the facets become darker and begin to swell quite uniformly. The process 

 extends around the margin, without very much swellmg, and then inward over the rest of the grain, 

 which may be crossed by fissures and so divided into several pieces which gelatinize independently. 

 The gelatinized grains are large and not much distorted except about the edges of the facets, and 

 have a very thick marginal ring which shows in some cases concentric bands of varying degrees of 

 darkness. Within the ring there is a lighter round or pyramidal area. 



The reaction with chromic acid begins in 30 seconds and is over in 7 minutes. The lamellaj and 

 hiluni become very prominent. The hilum begins to swell regularly and uniformly. The more 

 resistant outer part of the grain is formed into a thick marginal band, which is striated and very 

 distinctly marked by two or three alternate light and dark refractive and non-refractive rings 

 and bordered on the inside by a row of large granules or pyramids. The granules or pyramids 

 occasionally break off and move inwardly, where they are broken do\\'n. One point in the margin 

 protrudes, grows thin, and dissolves. The gelatinous granular material within the grain flows out 

 and is dissolved, followed by solution of the remaining portion of the margin. 



Reaction with purogallic acid begins in some grains in 30 seconds, and all are affected and nearly 

 all completely gelatinized in 45 minutes. The hilum and lamellae become very prominent. The 

 grains are covered with fine stricc, and the hilum swells until all the resistant outer substance forms 

 a striated, banded ring at the margin, which ring becomes thinner, clearer, and homogeneous as the 

 grain swells, until a gelatinous mass is formed. The gelatinized grain is large and somewhat dis- 

 torted and it maj- be much folded and sacculated, particularly at the distal end. 



The reaction with ferric chloride begins in a minute and is over in 5 minutes. The lamella; are 

 not entirelj' obscured. The hilum swells, as a dark bubble, the bubble grows larger, then shrinks, 

 and finally disappears. A marginal ring is formed, bordered by large granules on the inner side; 

 it gradually grows thinner antl clearer as the grain swells, and when the grain becomes very large the 

 ring moves inward from the side and thus gives the appearance of a hole in the grain. The 

 gelatinized grains are large and not much folded or crumpled, but somewhat distorted by the 

 invagination from the side already referred to. 



The reaction with Purdy's solution begins in some of the smaller and in the injured grains in 

 a minute and in the normal grains in about 10 minutes. After 30 minutes there is not much change, 

 and fully haff are never affected. The hilum and lamellte become very prominent. The reaction, 

 as far as it goes, is qualitatively like that with pyrogallic acid. 



