GENERA DRACUNCUI.US AND RICHARDIA. 449 



distinct the hilum swells rapidly, and a marginal band is formed which shows strisE and rather 

 indistinct alternate refractive and non-refractive parts. Deep fissures at the hilum disappear as 

 though they were merely invaginations from the outside that had become pushed out as the 

 inner part of the grain swells. The marginal band gradually becomes thinner and clearer and 

 appears in the form of a large capsule somewhat folded and distorted, but still retaining much 

 of the original form. Rarely, the capsules are so much folded and creased that they resemble 

 granular masses. 



Reaction with ferric chloride begins in 2 minutes and is over in 45 minutes. The hilum becomes 

 distinct, often as a dark spot or a fissure. The lamellae are not apparent or indistinct. The margin 

 becomes clear and darker, causing the inner portion to appear light and opaque by comparison. 

 There is rarely slight gelatinization with saccular protrusion at certain points on the margin, espe- 

 cially if the grain does not react quickly. The hilum swells, or the substance within the grain dis- 

 solves and extrudes at this point. A marginal ring is formed which appears to be homogeneous; 

 neither striae nor refractive and non-refractive bands could be made out. The swollen grains are 

 very large and obscure, not much distorted, unless there has been preliminary gelatinization of the 

 margin, in which case they are very greatly distorted and show many sacculations. 



The reaction with Purdy's solution begins very slightly in 2 minutes and is over in 30 minutes, 

 but at least one-third of the total number of grains are not affected. The hilum and lamellae become 

 somewhat more distinct. The hilum swells slightly and the grain becomes divided by fine striae, 

 which become more distinct as the swelling of the hilum progresses. A marginal ring is formed 

 consisting of two layers, the inner being composed of large granules and the outer of a striated band 

 marked with concentric, refractive and non-refractive parts. This marginal ring soon becomes 

 clear, thin, and homogeneous, and the grain is finally fully gelatinized. The gelatinized grains thus 

 formed are fairly large, not much crumpled or wrinkled, and retain much of the original shape. 



GENUS RICHARDIA. 



The basis of this genus consists of a few well-marked species, natives of South Africa. Some 

 species and several varieties are in common cultivation and are popularly known as callas, which, 

 however, like the Arum callas, do not belong to the true monotypic genus Calla. Starches were 

 prepared from the rhizomes of 3 well-known species: R. ellio(iana Knoth. {Calla elliotiana, Hort.), 

 the golden calla; R. africana Kunth., the common calla Hly or Ethiopian lily, or Lily-of-the-Nile; 

 and R. alho-maculata Hook., the spotted calla. 



STARCH OF RICHARDIA ELLIOTIANA. (Plate 16, figs. 91 and 92. Chart 81.) 



Histological Characteristics. — In form the grains are simple and usually isolated, with some 

 aggregates of two, three, four, or more grains. The most conspicuous forms are polygonal, formed 

 by a number of pressure facets; spherical and ovoid forms appear to be the fundamental tj^pes, 

 but have been modified by mutual pressure, so as to be converted into pentagons, hexagons, and 

 other polygonal forms; there are also dome-shaped and hemispherical, with one, two, or three or 

 more small facets at the base; triangular; ovoid and spherical forms, with one or two small facets; 

 and various indefinite forms. The facets are sharply defined. A given grain may have different 

 shapes according to the aspect in which it is seen, owing to variations in the number, size, and distri- 

 l)ution of the facets. For instance, on one end the dome-shaped and hemispherical grains appear 

 spherical, and on the other end the surface is irregular, owing to the facets. 



The hilum is a fairly distinct, small, round, non-refractive spot, centrally or slightly eccentric- 

 ally placed, rarely marked by a transverse or a 3-armed fissure; but the figure appears as if it were 

 beneath the surface of the grain and without communication with the outside. Double or multiple 

 hila were not seen. 



The lamellcB are only rarely distinct, when one or two may be seen especially large and promi- 

 nent, one near the hilum and the other about midway between it and the margin. They are regular, 

 concentric rings and do not follow the outline of the grain. 



The grains vary in size from 1.4 to 18^. The common size is 12//. 



Polariscopic Properties. — The figure is well defined, centric or slightly eccentric, and in the form 

 of a cross. The lines are of nearly the same size and distinctness throughout and rather sharply 

 defined. Very rarely, owing to an elongation or other abnormality of the hilum, the figxu-e appears 

 as a solid line bisected at each end. 



