344 



STARCHES OF GRAMINACE^. 



In Z. mays var. aviylea-saccharala " the external appearance of the grain is that of a sweet, but exami- 

 nation shows that the lower half of the kernel is starchy, the upper half horny and translucent." 

 East has recently pointed out (Science, 1909, xxix, 465) that the "sweet corn varieties do not 

 belong to a unit group, but consist both of dent corns and of flint corns which have lost their original 

 starch-forming power." It is of interest to note that it has been shown by Correns (Bibliotheca 

 Botanica, 1901 ; quoted by East) that the presence or absence of the starch-forming property acts 

 as an independent character pair in inheritance. 



The specimens of starch studied in this research fall, according to the foregoing data, under the 

 following heads: 



Z. mays var. everta (Golden Queen and White Rice). 

 Z. mays var. indurata (North Dakota, and Compton's Early). 

 Z. mays var. indentata (Early Learning, and Hickory King). 



Z. mays var. saccharata (Stowell's Evergreen, a dent sweet corn; and Black Mexican and 

 Golden Bantam, both flint sweet corns). 



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



Histological Characteristics. — Inform all of the grains are simple and isolated, with the excep- 

 tion of components of a few small aggregates and many clumps. The grains are more or less angular, 

 owing to mutual pressure, and many have three or four or more pressure facets. The surface is usually 

 irregular owing to the pressure facets. The conspicuous forms are polygonal, with sharp or rounded 

 angles, iLsually 4- to 6-sided; oval, round to nearly round, both sometimes faceted. There are some 

 ovoid, hemispherical, and triangular forms. 



The hilum, when it can be made out, appears either as a small or large, usually centric or occa- 

 sionally slightly eccentric, round or irregularly shaped cavity which in most grains has radiating 

 from it three small, regular, narrow fissures. The presence of the cavity may be due to the begin- 

 ning of gelatinization caused by the heat of grinding the seeds. In many of the grains extensive 

 and irregular fissures nearly divide the grain into two or more pieces. 



The lamellcB are not demonstrable. 



The size varies from the smaller, which are 4 by 4/j, to the larger, which are 18 by 18^ or 18 

 by 14a» in length and breadth. The common size is 12/i. 



Polariscopic Properties. — The ^ure is usually centric, 

 distinct, fairly clear-cut, and usually regular. The lines 

 are generally straight and at right angles. 



The degree of polarization is fairly high. It varies 

 somewhat in different grains, but not much in different 

 aspects of the same grain. 



With selenite the quadrants are generally well defined, 

 irregular in shape, and unequal in size. The colors are 

 usually pure. 



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

 tion, the grains all color a fair violet; with a 0.125 per 

 cent solution they color lightly, and the shade does not 

 deepen rapidly. After heating in water until all the 

 grains are completely gelatinized, the solution colors 

 fairly and the gelatinized grains very deeply on the addi- 

 tion of iodine. After boiling for 2 minutes the solution 

 colors very deeply, but the gelatinized grain-residues not 

 at all. The capsules become a reddish-violet color with 

 an excess of iodine. 



Staining Reactions. — When viewed in masses, the grains show a slight tint of violet at once with 

 gentian violet. After remaining in the solution for 30 minutes they are lightly and unevenly stained. 



With safranin the grains, when viewed in masses, show a slight tint of pink at once. After 

 remaining in the solution for 30 minutes they are very lightly and unevenly stained. The color 

 is generally deeper at the hilum or the fissures at this point. 



Temperature Reaction. — The temperature of gelatinization is 62.5° to 64° C, mean 63.25°. 



PS 01 PA < 

 ~ PC PS 



Curve of Reaction-Intenrittea of Starch of Zea mays 

 var. everta (Golden Queen). 



