GENERA GLADIOLUS AND WATSONIA. 



721 



aart No. 276. 



PS CI PA 

 ~ POPS 



NOTES ON THE STARCHES OF GLADIOLUS. 



These starches show more or less conspicuous differences in their gross histology, G. primulinus 

 and G. floribundtis being notably smaller than G. byzantinus, G. cardinalis var. (Blushing Bride), 

 and variations occur particularly in form and lamellation in the several starches. In the reactions 

 the differences permit of ready diagnosis; every reaction shows more or less noticeable differences, 

 the sum of which in the case of each starch is definitely diagnostic. 



GENUS WATSONIA. 



The genus Watsonia includes 16 species of bulbous plants, natives of the Cape of Good Hope, 

 except a single species that is native to Madagascar. This genus in its essential l)otanical characters 

 is closely akin to Gladiolus. Starches from 3 sources were examined, including 2 species and 1 

 variety: W. humilis Mill., W. iridifolia var. o'brieni (W. alba Hort., W. o'brieni Mast., W. iridifolia 

 var. alba Rob., W. meriana var. alba Hort.), and W. meriana Mill. 



STARCH OF WATSONIA HUMILIS. (Plate 70, figs. 415 and 416. Chart 276.) 



Histological Characteristics. — Inform the grains are simple, and except the small ones are almost 

 wholly in the form of aggregates consisting of two or more components, usually two or three, the 

 lines of union commonly being indicated by fissures. In some cases the aggregates have the appear- 

 ance of a combination inclosed by a common layer of starch, thus making a compound grain. Owing 

 to the tendency of the aggregates to remain adherent, isolated grains having pressure facets are not 

 common. The conspicuous forms of the aggregates are the ovoid and spherical, with transitional 

 forms; also some ellipsoidal forms, mostly made up of 

 two grains of unequal size. The grains are not flattened, 

 hence when seen on end they appear to be spherical. In 

 comparison with starches generally there is a very large 

 proportion of small grains which are spherical, oval, 

 and polygonal. 



The hilum is large and generally very distinct, usu- 

 ally somewhat eccentric, and often appears to be a cavity 

 extending to the inner part of the grain. It usually is 

 round, elongated in a few cases, and sometimes fissured. 

 The fissuration may be observed as a simple, clear-cut, 

 transverse Hne, or irregularly stellate. Lines, or fissures, 

 deep or shallow, frequently exist at the Hues of union of 

 the grains composing the a^regates. There may be 2 or 

 3 hila, depending upon the number of component grains. 



The lamellce are usually fairly distinct. They are 

 rather coarse, commonly regular, continuous concentric 

 rings, and those nearer the hilum are generally the most 

 distinct. Some of the lamellae, at parts distal to the 

 hilum, are curved so that they may not correspond with 



the form of the marginal outline. In such cases a part of the aggregate has presumably broken away 

 and later has been covered with secondary layers of starch. Otherwise the lamellse follow regularly 

 the outline of the margin. There are about 8 to 9 lamellaj on the larger grains. 



The single grains vary in size from 1.5 to 20/u. The aggregates are as large as 28/1. The common 

 size of the doublets is 16/i. 



Polariscopic Properties. — The figure is distinct, fairly clear-cut, and fairly regular. Some of the 

 grains may show lines which become broader, yet distinctly defined at the margin. In many 

 grains the central part of the figure is a large, dark area of irregular outline, and in a few only 

 marginal parts of the grains are observed. 



The degree of polarization is fairly high. It varies very much in different grains, but not greatly 

 in different aspects of the same grain. 



With selenite the quadrants are generally not clear-cut, are usually irregular in shape, and some- 

 what unequal in size. The colors are generally pure. 



Iodine Reactions. — With 0.25 per cent Lugol's solution the grains are colored a light violet 

 and the color deepens very slowly; with 0.125 per cent solution they tint very lightly and the color 



VL VL 60* 



Curve of Reaction-Intensities of Starch of Watsonia 

 humilis. 



