GENUS POLYGONUM. 



419 



Reaction with chromic acid begins at once and is over in a minute. The hilum becomes clear, and 



the less resistant starch, occupj'ing the central part of the grain, swells evenly in all directions. The 

 more resistant starch forms a fairly broad, dense band at the margin, which rajiidly is transformed into 

 a thin and transparent envelope or capsule. This capsule is dissolved at one point, and the inclosed 

 semiliquid starch flows out and is rapidly dissolved, solution of the rest of the capsule following. 



The reaction with pyrogallic acid begins in 1 5 to 30 seconds and is over in 3 minutes. The hilum 

 becomes clear, and the less resistant starch is gelatinized and swells and occupies the central portion of 

 the grain. The more resistant starch forms a broad, dense marginal band which becomes less broad 

 and dense until it forms a rather thick but nearly transparent capsule. The gelatinized gi'ains are 

 large and retain some of their original form. The capsules are somewhat folded and wrinkled. 



With ferric chloride reaction begins in a few grains in a minute. It is over in two-thirds of the 

 grains in 10 minutes, in nearly all in 25 minutes, and in all in 35 minutes. The reaction begins at 

 the corners and edges of the facets, and the starch at these points becomes gelatinous and swells 

 out irregularly. The less resistant starch l)ccomes gelatinized and occupies the central part of the 

 grain, while the more resistant starch forms dense but not very broad masses at the margin, separ- 

 ated by the gelatinized starch of the corners and edges of the facets. Gradually the more resistant 

 starch is gelatinized. The gelatinized grains are large and do not retain much of the original form. 

 The capsules are often much wrinkled and crumpled. 



The reaction with Purdy's solution starts in many grains in 30 seconds. Two-fifths are partially 

 gelatinized in 20 minutes, with an incomplete reaction in an hour. The reaction appears to be the 

 same qualitatively as that with pyrogallic acid. 



STARCH OF POLYGONUM FAGOPYRUM VAR. (JAPANESE). (Plate 10, figs. 50 and 60. Chart 63.) 



Histological Characteristics. — In form the conspicuous shapes and other features of the gross 

 microscopical characters of the grains are identical with those of American buckwheat. 



The hilum or cavity with radiating fis.sures in this region is practically identical with that 

 of American buckwheat. 



Lamellae are not visible. 



The grains vary in size from the smaller, which are 

 2n, to the larger, which are 12/i. The common size is B>fx. 



Polariscopic Properties. — The figure is centric or 

 slightly eccentric and identical in its characters with that 

 of American buckwheat. 



The degree of polarization is fair to rather high. In the 

 specimen studied there was a larger proportion of grains in 

 which polarization is high than in American buckwheat. 



With selenite the character of the quadrants and 

 colors are identical with those already described for 

 American buckwheat. The yellow appeared slightly 

 brighter and purer in a greater proportion of the grains 

 than in American buckwheat. 



Iodine Reactions. — With 0.25 per cent Lugol's solu- 

 tion the grains color a light violet and darken very slowly. 

 The color is lighter and slightly more reddish in tint than 

 in American buckwheat; with 0.125 per cent solution 

 the grains color slowly a light old-rose which deepens 

 slightly in 5 minutes. The grains, with this weaker reagent, also show more of a reddish color than 

 those of American buckwheat. After heating in water until all the grains are completely gelatinized, 

 the solution colors a deep blue-violet and the gelatinized grains a rather deep reddish-violet on the 

 addition of iodine. After boiling for 2 minutes, the solution colors a very deep reddish-blue, but the 

 grain-residues do not color at all. When an excess of iodine is added the capsules color a deep red- 

 violet to wine-red. There is more of a reddish tint in the Japanese than in the American buckwheat. 



Staining Reactions. — With gentian violet and with safranin the grains begin to stain very lightly 

 at once and in 30 minutes they are still very lightly stained. The color is the same as that of American 

 buckwheat. 



Temperature Reaction. — The temperature of gelatinization is 64.5° to 65° C, mean 64.75°. 



p I nv T p 

 s 



Chart No. 63. 



GV S T CI CA FA FC P S CIPA CA 



PC PS 

 5 



Curve of Reaction-Intensities of Starch of Polygonum 

 fagopyrum var. (J^P^i^csc)* 



