878 



STARCHES OF PRIMULACEiB. 



STARCHES OF PRIMULACE/E. 



Class, Dicotyledones. Order, Primules. Family, Primulacese. Genus 



represented. Cyclamen. 



The Primulacea comprise about 25 genera and 315 species of herbaceous plants, for the most 

 part natives of the Northern Hemisphere, chiefly of temperate and alpine regions, including many 

 of the most highly prized species of garden plants. 



GENUS CYCLAMEN. 



Cyclamen is a genus of about a dozen species of low, tuberous herbs, natives of the Mediterranean 

 region and Western Asia. The fondness of swine for the tubers or corms led to the vulgar name sow- 

 bread, that was formerly applied to the genus. Starches from two species were prepared, C. repmidum 

 Hort. and C. coum Mill., both from Southern Europe, the former probably a variety of the latter. 



STARCH OF CYCLAMEN REPANDUM. (Plate 99, figs. 589 and 690. Chart 387.) 



Histological Characteristics. — In form the grains are usually simple. There are a few compound 

 grains consisting of two components, with a few aggregates. Not infrequently several very small 

 grains adhere to the distal end of one of the large grains. There is no tendency to form in clumps. 

 There are pressure facets on some of the isolated grains. 

 The surface of the grains is quite smooth, except when 

 rendered irregular by nipple-like processes or pressure 

 facets. The conspicuous forms are ovoid; oval, which 

 usually have the distal end pointed and a small hole or 

 depression at the end; and round or nearly round; also 

 pyriform, dome-shaped to hemispherical, angular with 

 rounded or sharp comers, elliptical, and some indefinite 

 forms. The grains are not flattened. 



The hilum is a comparatively small, round non- 

 refractive spot, eccentric usually from one-fourth to one- 

 sixth of the longitudinal axis of the grain, and on or to 

 one side of the median line. Frequently there are 2, 3, 

 or more hila in one grain, separated from one another by 

 small fissures. They appear sometimes to be connected 

 by a line and may not be of the same size. In one grain 

 the hilum appeared to be an elliptical spot expanded at 

 each end. Fissuration is rare. 



The lameUcE are distinct, rather fine, and decidedly 

 irregular. There appear to be two sets in many grains, 

 one appears to partially or completely inclose the other; the internal system may be very large or 

 very small, and it may lie transversely or diagonally to or in the same direction as the long axis of 

 the inclosing system. If there are two hila, each has its set of lamellae, at first separate and then 

 fused. The lamellae nearest the hilum are the larger and more distinct. There are usually about 20 

 on the larger grains. 



The grains vary in size from 5 to 48)u. The common size is 28/i. 



Polariscopic Properties. — The figure is eccentric and very distinct. Four lines are visible. 

 These are frequently much bent and otherwise distorted because of irregularities of the surface of 

 the grain and the presence of the two sets of lamellae. If there are more than one hilum, each shows 

 the beginning of a figure of which two lines unite with the lines of the figure from another hilum 

 and do not extend farther, or they may fuse and be prolonged along the long axis of the grain. 

 Double and curiously modified figures are occasionally noted. 



The degree of polarization is high. At some points it is almost absent owing to thinness of 

 the grain, at others very high, owing to thickness of the grain. It varies according to the aspect 



Curve of Reaction-Intensities of Starch of Cyclamen 

 repandum. 



