GENUS ZEA. 



351 



Chart No. 7. 



CA PA FC P S CI PA CA 



Curve of Reaction-Intensities of Starch of Zea mays 

 var. saccharata (Stowell's Evergreen). 



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

 The lines are straight and generally at right angles. 



The degree of polarization is fairly high. It does not vary much in different graias, or in dif- 

 ferent aspects of the same grain. It is higher than in Golden Queen. 



With selenite the quadrants are commonly fairly well defined, irregular in shape, and for the 

 most part unequal in size. The colors are not quite pure. 



Iodine Reactions. — With a 0.25 per cent Lugol's solution the grains all color a fairly deep violet; 

 with a 0.125 per cent solution they color lightly, and the shade does not deepen rapidly. The colora- 

 tion is slightly more than in Goklen Queen. After heating 

 in water until all the grains are completely gelatinized, 

 the solution colors fairly and the gelatinized grains very 

 deeply on the addition of iodine. After boiling for 2 

 minutes the solution colors very deeply, but the gelatin- 

 ized grain-residues not at all. The capsules all color red- 

 violet on the addition of an excess of iodine. 



Staining Reactions. — With gentian violet the grains 

 stain very slightly at once, but after remaining in the 

 solution for 30 minutes there is very little change. 

 The color is somewhat deeper at the central fissure. 

 Large, oval, simple grains, in addition to the angular 

 grains, are occasionally noted, but they also stain very 

 lightly. The reaction is less than in Golden Queen. 



With safranin the grains stain very slightly and 

 evenly at once, and after remaining in the solution for 

 30 minutes there is very little change. The stain is deep 

 if the central fissure is broad, and also at eroded points 

 on the surface of the grain. The reaction is less than in 

 Golden Queen. 



Temperature Reaction. — The temperature of gelatinization is 66.2° to 67.5° C., mean 66.85°. 



Effects of Various Reagents. — With chloral hydrate-iodine the grains begin to react at once; a 

 few are gelatinized in 30 seconds, the majority in 2 minutes, and all in 6 minutes. The reaction is 

 the same qualitatively as in Golden Queen. 



The reaction begins in a few seconds with chromic acid. A few grains are dissolved in a minute 

 and all in 3 minutes. The reaction is the same qualitatively as in Golden Queen. 



The reaction with pyrogallic add begins at once. Many of the grains are gelatinized in 30 

 seconds and all in 2 minutes, with the exception of scattered grains (one in several hundred), in 

 which latter the reaction is complete in 4 minutes. The reaction is qualitatively the same as in 

 Golden Queen, but the gelatinized grains are less irregular in outline. 



With /crric chloride the reaction begins at once; a few are gelatinized in 2 minutes, the majority 

 in 5 minutes, and all in 10 minutes. The reaction is the same as in Golden Queen, except that the 

 striated border is seen in fewer grains and the gelatinized grains are less irregular. 



The reaction begins at once with Purdy's solution. A few small grains are gelatinized in IJ-^ 

 minutes and about one-tenth in 30 minutes. The reaction is very incomplete at the end of an hour. 



STARCH OF ZEA MAYS VAR. SACCHARATA (BLACK MEXICAN, A FLINT SWEET CORN). 



(Plate 1, figs. 1 and 2. Chart 8.) 



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

 a few that occur in small aggregates and clumps. The isolated grains each usually have five or six 

 pressure facets. The surface of the grains is usually irregular, owing to pressure facets which differ 

 in size, position, and number of the facets. The conspicuous forms are polygonal which usually 

 have four or five facets having sharp or somewhat rounded angles, round or nearly round, and 

 oval. Ther(! are also triangular, dome-shapeil, and hemispherical grains. 



The hilum is centric or slightly eccentric, and when it is not fissured is an indistinct, small or 

 large round spot, or a round or irregularly shaped, rather large, distinct cavity. In many others 

 there are one or more ragged irregular fissures; and in a few there is a single short, straight, narrow 

 line traversing the hilum. 



The lamelloe are not demonstrable. 



