GENERA ZEA AND ANDROPOGON. 367 



saccharalcD licing very low, those of the evcrtoe on the whole higher, and the induralce and indenlalce 

 the highest and the same. Likewise is there grou]iing in the temperature reactions, the evcrlcB 

 having the same and the lowest temperature of gelatinization (03.25°), the induralm the highest 

 (G8° and 68.5°), and the indentatce and saccharatoe about the same and of an intermediate standard 

 (66.5°, 66.75°, 66.85°, 65°, and 66.5°; mean 66.31°), with perhaps the saccharala having a somewhat 

 lower temperature than the indentatw. Grouping is also indicated in the chloral hydrate-iodine 

 reaction, the everiw being the most sensitive, and then in order the saccharatw, the indentatce, and 

 induratce. In both the chromic acid and pyrogallic acid reactions the evertm and saccharatoe appear, 

 on the whole, to be more sensitive than the induratce and indentatw, and a corresponding condition 

 is suggested in the ferric chloride records. With Purdy's solution the reactions are slow, so much so 

 that at the end of an hour gelatinization is incomplete in all of the starches; but if the relative in- 

 tensities of the reactions are taken at the end of 30 minutes, there will be foimd clear evidences of 

 grouping: about 33 per cent of the evertce starches being gelatinized, only a few grains of the induratce, 

 about 20 per cent of the indentatce, and an average of 47 per cent (10, 80, and 50 per cent, respec- 

 tively) of the saccharatoe. From the foregoing data it seems clear that by careful experimentation 

 and by extension of the methods there should be no difficulty in not only distinguishing one form 

 of Zea starch from another, but also in positively specifying the group to which it belongs. 



GENUS ANDROPOGON. 



The polymorphous genus Andropogon contains a number of species that have been found 

 useful for forage, ornamental, medicinal, textile, or other economic purposes. Included here are 

 the various cultivated forms of sorghum, which are regarded by some authorities as having been 

 derived from Andropogon halpensis Brot., and by others as having come from A. sorghum Brot. (Sor- 

 ghum vidgare Linn.). The sorghums, Hitchcock notes, fall into three classes, in accordance with their 

 uses: (1) Broom corn, used in the manufacture of brooms; (2) sugar or saccharine sorghum, culti- 

 vated for the sweet juice, etc.; and (3) non-saccharine sorghum, grown for forage and seed. Starches 

 were prepared from three forms, all of which belong to the non-saccharine group. 



STARCH OF ANDROPOGON SORGHUM VAR. (WHITE KAFFIR CORN). 

 (Plate 1, figs. 3 and 4. Chart 10.) 



Histological Characteristics. — In form there are both simple and compound grains, almost solely 

 the former. The simple grains are isolated, excepting a few that are found in aggregates. The 

 conspicuous forms of the single grains are polygonal, round, and rounded oval. Triangular grains, 

 with a rounded apex and curved base, and lenticular forms are rarely observed. Among the aggre- 

 gates there is often one large grain having a globular grain fitted into a slight depression. There 

 are also doublets formed of components of equal size. The isolated grains arc usually dome-shaped 

 with either a flattened or a pointed base. There are a number of partially gelatinized graiias in the 

 preparation. 



The hilum is a fairly refractive, round spot, which is centric in most of the grains and very 

 slightly eccentric in some of the oval forms. Multiple hila, without lines of separation, are observed 

 in some of the grains. Generally there is at the hilum either a cavity or one or more clefts which 

 usually form a cross or a Y, although sometimes there is a clean-cut, slightly curved, transverse 

 cleft, and occasionally a much-branched fissure. The last-named type of fissuration is probably 

 due to the beginning of gelatinization of the grain. 



The lamellce are not generally visible, and neither the character nor number can satisfactorily 

 be determined. 



The grains vary in size from the smaller, which are 2 by 2/i, to the larger, which are 22 by 26;u, 

 and 26 by 26/i in length and breadth. The common size is 16 by 16/i. 



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

 cut. The lines of the figure are thick and generally straight, broadening towards the margin. In 

 some grains a large central area is dark. 



The degree of polarization is high, but varies sometimes in one aspect and in different aspects 

 of a grain. 



With selenite the quadrants are clearly defined, but often irregular in shape and unequal in 

 size. The colors are pure. 



