GENUS ZEA. 345 



Effects of Various Reagents. The grains begin to react at once with chloral hrjdrate-iodine. 

 Most are gelatinized in 30 seconds and all in 4 minutes. The grains color an old-rose at once, and 

 a dark spot or line appears at the hilum. The color deepens at one or more points on the margin 

 and spreads towards the hilum, around which a lighter area persists for some time; finally, the 

 entire grain is colored a deep purple, the area around the hilum having a slightly lighter tint. 

 During gelatinization the swelling is usually uniform, so that the gelatinized grain commonly retains 

 the general shape of the untreated grain. 



The grains begin to react at once with chromic acid. A few are dissolved in 20 seconds and all 

 in 75 seconds. The starch around the hilimi becomes clear, and delicate stride radiate from this 

 central mass. The grain swells imiformly and gradually becomes gelatinized. The envelope is 

 finally ruptured, and with the extruded contents is completely dissolved. 



The reaction with pyrogalUc acid begins at once. A few grains are gelatinized in 20 seconds 

 and all in 35 seconds. The hilum appears as a clear spot, or a deep fissure at this point becomes 

 clearly marked. The clear space around the hilum enlarges, and fine striae radiate from this central 

 mass towards the margin. The grain swells uniformly, and the starch-substance, with exception of 

 the capsule and possibly an outermost lamellar layer, becomes entirelj^ gelatinized. The gela- 

 tinized grain is slightly WTinkled, but it retains the general shape of the untreated grain. 



With ferric chloride the reaction begins at once. A few grains are gelatinized in a minute, most in 4 

 minutes, and all in 10 minutes. The hilum, or the cleft at this point, becomes very distinct. The 

 hilum or cleft enlarges, a bubble is formed, and fine striae radiate from hilum or cleft or from the 

 gelatinized portion around the hilum towards the margin. The gi-ain swells, the bubble collapses, 

 there is an invagination at one end, and all of the gi-ain becomes gelatinized, with the exception, ap- 

 parently, of a marginal layer and a few refractive granules. Sometimes an irregular striated border 

 of more clearly defined lamellae appears, which may be ruptured at one or more points, and the grain 

 then swells rapidly at these places. Gelatinization proceeds until the entire grain is involved. The 

 gelatinized grain is swollen and somewhat irregular in shape, but retains in general the form of the 

 untreated grain. 



The reaction begins at once with Purdy's solution. A few grains are gelatinized in a minute 

 and about one-third in 30 minutes, and there is little further reaction in an hour. The hilum or 

 the cleft at this point becomes more distinct, and usually two and sometimes three or four clear, 

 prominent lines, as well as numerous fine striae, pass from the hilum or cleft towards the margin. 

 The lamelte become sharply defined and the grain swells, but there is no further change in most 

 of the grains even when kept under observation for 30 minutes. In a few grains in which gelatini- 

 zation is practically completed the space around the hilum gradually clears until the entire grain is 

 gelatinized; or if there is a cleft at the hilum with three or more deep, radiating fissures, the solution 

 of the two proceeds along their course. When the cleft at the hilum is very deep a bubble is some- 

 times formed here which increases in size with the swelling of the grain and then suddenly collapses. 

 The gelatinized grains are swollen, but retain in general the shape of the untreated grain. 



STARCH OF ZEA MAYS VAR. EVERTA (WHITE RICE). (Plate 1, figs. 1 and 2. Chart 2.) 



Histological Characteristics. In form the grains are simple and isolated, excepting a few that 

 occur in small aggregates and clumps. The surface of the grains is generally irregular, owing to 

 pressure facets. The conspicuous forms are the polygonal, with sharp or roimded angles, and having 

 usually four or five facets; the oval, and the round or nearly round, both sometimes faceted. There 

 are also some ovoid, triangular, and hemispherical grains. There are usually one or more pressure 

 facets on each of the grains. 



The hilum, when not fissured, may appear as a small or rather large round spot or cavity, 

 which is usually centric or slightly eccentric. It is generally fissured, and commonly there is an 

 arrangement of three rather small, narrow, regular fissures extencUng from a central ca\'ity. There 

 are grains which are nearly divided into two or more pieces by large, deep, irregular fissures. 



The lamellce are not demonstrable. 



The grains vary in size from the smaller, which are 4 by 4//, to the larger, which are 17 by 16^. 

 The common size is 12/i. 



Polariscopic Properties. The figure is usually eccentric, distinct, and generally clear-cut. In 

 some of the grains the lines grow broader and less well defined at the margin. They are commonly 

 straight and at right angles to one another. 



