352 



STARCHES OF GRAMINACEiE. 



Chart No. 8. 



GV S T CI CA PA rC P S CI PA CA 



Tho grains vary in size from the smaller, which are 2 bj' 2//, to the larger, which are 16 bj' lli^u. 

 The common size is lO/i. 



Poluriscopic Properties. The figure is usually centric, distinct, regular, and fairly clear-cut. 

 Sometimes the lines composing it are broad and not sharjily defined. The lines are also often curved 

 and generally placed at right angles to one another. 



The ilegree of polarization is low to fair. It does not vary much in different aspects of the same 

 grain, but in the same asjiect of a grain it is sometimes lower between one of the facets and the hilum 

 than elsewhere. It is nuich less than in Golden Qiicen and Stowell's Iilvergrecn. 



^Vith selenite the quadrants arc not well defineil, and are ordinarily irregular in shape and com- 

 monly unequal in size. The colors are less jjure than in Ciolden Queen and St<jweir.s Evergreen. 



Iodine Reactions. With a 0.25 per cent Lugol's solution tiie grains all color a fairly deep 

 violet; with a 0.125 per cent solution they color lightly. The color is slightly deeper than in Golden 

 Queen, but the same as in Stowell's Evergreen. After 

 heating in water until all the grains are completely gel- 

 atinized, the solution colors fairly and the gelatinized 

 grains very deeply on the addition of iodine. After boil- 

 ing for 2 minutes the solution colors very deeply, but 

 the gelatinized grain-residues not at all. The capsules all 

 color red-violet with an excess of iodine. 



Staining Reactions. With gentian violet the grains 

 are very slightly stained at once, and after remaining in 

 the solution for 30 minutes there appears to be no change. 

 The color is lighter than in Golden Queen and Stoweir.s 

 Evergreen. 



With safranin the grains are very lightly but unev- 

 enly stained at once, and after remaining in the solution 

 for 30 minutes there is very little if any change. The 

 color is less than in Golden Queen and about the same 

 as in Stowell's Evergi-een. 



Temperature Reaction. The temperature of gelati- 

 nization is 64 to 66 C., mean 65. 



Effects of Various Reagents. With chloral hydrate- 

 iodine the grains begin to react at once; all but a few scattered grains are gelatinized in 30 sec- 

 onds, and these scattered grains (one in several hundred) in 8 minutes. If the pressure facets are 

 strongly marked the deeper color appears first at the angles, or along one flattened siurface, and 

 gradually spreads over the grain. The reaction is qualitatively the same as in Golden Queen. 



The reaction begins at once with chromic acid. Some are dissolved in 20 seconds and all in 50 

 seconds. The reaction is qualitatively the same as in Golden Queen. 



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

 all in 40 seconds. The reaction is qualitatively the same as in Golden Queen. 



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 lamelliform layers are ruptured at more points at the 

 margin than in Stowell's Evergreen, and the gelatinized grain is more irregular in outline than 

 those of Stowell's Evergreen. The reaction is qualitatively the same as in Golden Queen. 



The reaction begins at once with Purdy's solution. A few grains ai-e gelatinized in 2 minutes, 

 and four-fifths in 30 minutes, but incomplete in an hour. The reaction is qualitatively the same 

 as in Golden Queen. 



STARCH OF ZEA MAYS VAR. SACCHARATA (GOLDEN BANTAM, A FLINT SWEET CORN). 



(Plate 1, figa. 1 and 2. Chart 9.) 

 Histological Characteristics. In form the grains are simple and isolated, with the exception of 

 a few small aggi-egates and clumps. Pressure fa(;ets appear on practically all (f th(^ isolated grains. 

 The surface of the grains is usually irregular, owing to pressure facets which dilTer in size, position, 

 and number on the different grains. The conspicuous forms are polygonal which usually have from 

 four to six facets, oval, and round to nearly round. Tliere are also a few dome-shaped to hemi- 

 spherical, triangular, and indefinite forms. 



Curve of Reaction-Intensities of Starch of Zea mays 

 var. saccharata (Black Mexican). 



