GENUS ANDROPOGON. 



359 



P I GV T P 

 S 



Chan No. 



CI 



CAPAFCPS CI PA CA 

 PC PS 



With Purdy's solution t,lu; rcaciion, wliicli consists in a little golatinization about the hiliim, 

 iiegins in some grains in a minute, hut the change docs not proceed much farther even at the end of 

 an lioiu". 



STARCH OF ANDUOl'OC.ON SORGHUM VAR. (YELLOW BRANCHING SORGHUM). 



(Plate 1, figs. 3 and 4. Chart 11.) 



Histological Characteristics. In form both simple and compound grains are present, almost 

 solol.v the former. There arc a hwv aggregates. Some of the grains have pressure facets. The con- 

 spicuous forms of the simph' grains are polygonal, round, and rounded oval. The isolated grains 

 are often dome-shaped or sugar-loaf-shajied. The aggregates frequentlj^ consist of one large grain 

 and one minute gi'ain. The grains very closely resemble those of White Kaffir sorghum. 



The hilum is a clear, rather refractive spot, which is centric in the round grains and slightly 

 eccentric in some of the oval and jiolygonal forms. There may be more than one hilum without 

 lines of separation. Sometimes three are arraiigcd at the angles of an imaginary triangle. Deep 

 clefts are usually foimd at the hihun, frequently ragged in character, and usually in the form 

 of a Y or diagonal cross. If but one cleft is found it is more often either slightly arched or 

 diagonally placed. The arrangements of the clefts are very similar to those noted in AVhite Kaffir 

 sorghum. 



The lamelloe are not usually visible, and neither their structure nor number could be determined, 

 as was also the case with White Kaffir sorghum. 



The grains vary in size from the smaller, which are 2 by 2ix, to the larger, which are 22 by 24;u 

 in length and breadth. The common size is 16 by IG/x. 



Fohiriscopic Properties. The figure is usually centric, regular, and very (.listinct. The lines are 

 thick, commonly straight, and broailening towartls the margin. There is a greater proportion of 

 figures with lines slightly bent than in White Kafhi- corn. 



The degree of polarization is high, occasionally vary- 

 ing slightly in the same aspect of a grain. It is a very 

 little higher than in White Kaffir corn. 



With selcnite the quadrants are well defined, and 

 usually unequal in size and irregular in shape. The colors 

 are pure. There is a greater variation among the quad- 

 rants as to size antl shape than in White Kaffir corn. 



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

 tion all the grains color a fairly deej) violet; with a 0.125 

 per cent solution they all color lightly, but the shade does 

 not deepen rapidly. It is slightly less than that of the 

 grains of White Kaffir corn. After heating in water until 

 all the grains are completely gelatinized the solution colors 

 lightly and the g(>latinized grains very deeply on the ad- 

 dition of iodine. After boiling for 2 minutes the solution 

 colors very deeply, but the gelatinized grain-residues not 

 at all. The capsules all color red or violet with an excess 

 of iodine. 



Staining Reactions. With gentian violet the grains 

 begin to stain at once. In 30 minutes they are lightly stained, some more than others. The 

 staining is slightly less than that of the grains of White Kaffir corn. 



With safranin the grains begin to stain at once; in 30 minutes they are lightly stained, some 

 more than others. The staining is slightly less than that of the grains of White Kaffir corn. ^ 



Temperature Reaction. The temperature of golatinization is 09.1 to 70.8 C, mean 69.95 . 



Effects of Varions Reagents. With chloral hydrate-iodine the reaction begins in most of the 

 grains in 30 seconds. It is complete in nearly all in 10 minutes, and in all in 15 mmutes. It is the 

 same qualitatively as that of the grams of White Kaffir corn. 



The reaction with chromic acid begins in some grains in 20 seconds and m all m 45 seconds, 

 and is over in 4 minutes. It is the same qualitatively as that of the grains of White Ivaffircorn. 



With pyrogallic acid the reaction begins in 30 seconds and is over in 3^ minutes. It is the 

 same qualitatively as that of the grains of White KafBir corn. 

 25 



Curve of Reaction-Intensities of Starch of Andropogon 

 sorghum var. (Yellow Branching Sorghum). 



