874 



STARCHES OF EUPHORBIACEiE. 



STARCHES OF EUPHORBIACE^. 



Class, Dicotyledones. Order, Geraniales. Family, Euphorbiacese. Genera 

 represented: Jatropha and Manihot. 



The Euphorbiacca include herbs, shrubs, and trees widely distributed in both temperate and 

 tropical regions, especially in South America, comprising 200 genera and over 3,000 species. Some 

 are poisonous, while others are edible; some are rich in starch; others yield castor oil, or croton 

 oil, or caoutchouc, etc., and some are cultivated as foliage plants, etc. 



GENUS JATROPHA. 



Jatropha is a genus of herbs and shrubs widely distributed in the warmer parts of both hemi- 

 spheres, especially in South America. It embraces about 68 species, some of especial importance 

 because of their richness in starch or oil. Starch was prepared from the roots of J. curcas Linn., 

 the French physic or purging nut, which is grown for ornamental purposes, and also on a large scale 

 in the Cape Verde Islands especially for the seeds or nuts, which yield a purgative oil. Other species 

 of Jatropha bear seeds that have a similar oil. 



STARCH OF JATROPHA CURCAS. (Plate 98, figs. 583 and 584. Chart 385.) 



Histological Characteristics. In form the grains are simple, isolated or in aggregates of two, 

 three, and four components. Nearly all the isolated grains have pressure facets. The grains are 

 rather irregular in outline, owing to the projections of the facets and to nipple-like or spicular 

 processes. On account of the latter, the forms are not so 

 regular as the faceted grains of other genera generally. 

 The conspicuous forms are dome-shaped to hemispheri- 

 cal, round to nearly round, ovoid, and oval. Various 

 polygonal and indefinite forms arise, chiefly through pe- 

 culiarities of the pressm-e facets or nipple-like and spicu- 

 lar jjrojections. In some aggregates the lines of demarca- 

 tion between the component grains can not be made out. 

 Seen from the side, they ajipear the same shape as from 

 above, while from the end they are seen to be spherical, 

 oval, or ovoid. 



The hilinn is a comparatively large refractive spot. 

 It may be round or elongated. If elongated, the form is 

 probably due in some grains to a slight fissure; but in 

 others it appears to be the actual shape of the hilum. 

 It is fairly distinct and occasionally marked by a shght 

 transverse or diagonal fissure, which may be divided. 

 It is centric or eccentric from slightly to about two- 

 fifths of the longitudinal axis and slightly to one side 

 of the median line. There are rarely double hila. 



The lameUce are distinct, rather coarse, refractive and non-refractive rings. When an elongated 

 hilum is present they are elliptical rather than circular; in other grains they are circular. Those 

 nearest the hilum and in the central parts of the grain are coarser than those nearer the margin. 

 They vary also in size and distinctness in different grains. In number they vary from 6 to 15. 

 There are about 10 on a medium-sized grain. 



The grains vary in size from 4 to 32^, commonly 16/*. 



Polariscopic Properties. The figure is centric or eccentric and very distinct. The four lines 

 of the cross are usually of about the same size and distinctness throughout their length, though 

 some may be broader at the margin or elsewhere. If the hilum is elliptical in form, the figure is a 

 single dark line divided at each end, instead of a well-marked cross. 



Curve of Reaction-Intensities of Starch of Jatropha 

 curcas. 



