366 STARCHES OP GRAMINACEjE. 



and then over all parts. The gelatinized grains are not very large, they are of a uniform dark indigo 

 color, and retain much of their original form. 



The reaction with chromic add begins in some of the grains in 15 to 30 seconds and is over in 

 25^ minutes. The hilum becomes more distinct, and coarse striae appear which radiate from the 

 hilum in all directions. The less resistant starch is transformed into a semiliquid mass which occu- 

 pies the central portion of the grain, thus causing the whole grain to swell gradually and equally 

 in all directions and forcing the more resistant starch into the form of a fairly broad, coarsely striated, 

 marginal ring which shows two or tlu-ee concentric refractive and non-refractive bands, the remains 

 of the lamellar structure. These bands fade gradually as the marginal ring grows thinner and clearer, 

 until there is a thin, homogeneous-looking, clear envelope. This envelope or capsule is now indented 

 at one point, solution occurring at the bottom of the indentation. The semiliquid contents flow out 

 through this opening and dissolve, followed by solution of the envelope. 



The reaction with pyrogallic acid begins in most of the grains in 30 seconds and is over in 3 

 minutes. The hilum and lamellae often become more distinct, and striae appear radiating from the 

 hilum throughout the grains. The less resistant starch passes rapidly into a gelatinous mass which 

 occupies the center of the grain, causing the grain to swell rapidly. The more resistant starch is 

 forced to the margin, where it forms a striated band, which, as the' grain swells rapidly, becomes a 

 thin and clear envelope. The resulting swollen grain is very large, and the envelope is often invagin- 

 ated, folded, and wrinkled, the folds sometimes being concentric and seeming to follow the lines 

 of the prominent lamellae. 



The reaction begins in a few grains in a minute with ferric chloride. About half are completely 

 gelatinized in 30 minutes, and three-fourths in an hour. The central portion of the grain assumes 

 a granular appearance; the starch at one or two points on the margin begins to gelatinize, and the 

 process spreads from these points either about the margin, leaving the central portion for a time 

 ungelatinized, or it spreads over the whole grain, the margin not being gelatinized before the adjacent 

 central portion. The gelatinized grains are very large, with wrinkled and folded capsules. 



With Purdy's solviion the reaction begins in a few grains in 20 seconds, about two-thirds are 

 gelatinized in 5 minutes, nine-tenths in 10 minutes, and all in 25 minutes. The reaction is the same 

 in appearance as that to pyrogallic acid. 



STARCH OF TRITICUM SATIVUM VAR. DICOCCUM. (Plate 2, figs. 9 and 10. Chart 16.) 



Histological Characteristics. — In form the grains are simple and for the most part isolated. A few 

 have pressure facets. The grains vary rather more in form and are more irregular in outline than in 

 the specimen of T. sativum var. vulgare. The conspicuous forms are the same as T. sativum var. vul- 

 gare, but there are more of semicircular forms and grains having their outline flattened at various 

 points. A larger proportion of grains of this preparation were partially gelatinized than in the first 

 specimen. One grain of T. sativum var. vulgare was deeply fissured in the process of breaking apart 

 in the middle, and since aggregates in the form of doublets with grains of equal size were not observed 

 it is quite possible that the large hemispherical grains referred to are half grains. There are a few 

 minute globular and ovoid grains, but they are not nearly so numerous as in T. sativum var. vulgare. 

 More of the small grains are spindle-shaped, and the aggregates usually consist of clusters of rather 

 larger grains than those noted in the other variety, and the components appear to be mostly of the 

 pointed type. The grains are usually broader than thick. 



The hilum and cleft have the same characters and structure as noted for T. sativum var. vulgare. 



The lameUce are visible in a larger portion of grains than in T. sativum var. vulgare. Since the 

 lamellae are usually more clearly marked in grains which are undergoing gelatinization or solution, 

 it is probable that the relative prominence of the lamellae in this specimen is to be attributed to this 

 cause. There were ten to fourteen lamellae counted on some of the large grains. 



The grains vary in size from the smaller, which are 2 by 2fi, to the larger, which are 40 by 30/u 

 and 32 by 32p. The common size is 22fi. 



Polariscopic Properties. — The figure is usually centric, but occasionally slightly eccentric. The 

 lines of the figure are similar to those noted in T. sativum var. vulgare, but in a greater number of 

 grains they are very indistinct, and more often either bent or bisected. 



The degree of polarization is very low in the large grains to fair in a few of the smaller grains. 

 Variations are usually observed in the same aspect of a grain. It is high when the grains are viewed 

 on edge. It is lower on the whole than in T. sativum var. vulgare. 



