744 



STARCHES OF IRmACE^. 



Chart No. 289. 



I GV 

 S 



PS CI PA, I 

 ~ PC PS 



STARCH OF CROCUS SUSIANUS (CLOTH-OF-GOLD). (Plate 74, figs. 441 and 442. Chart 289.) 



Histological Characteristics. Inform the grains are simple. They are partly isolated and partly 

 either in aggregates which consist of two or more components or in clumps consisting of many 

 grains. Well-marked pressure facets are very common. The surface of many grains is irregular, 

 owing to depressions and ridges. The conspicuous forms are polygonal, dome-shaped with either 

 a flattened or pointed distal end, and round or nearly round; also ellipsoidal with slightly flattened 

 distal end, bell-jar-shaped, sugar-loaf, and imperfect rhomboidal grains. The aggregates may con- 

 sist of components of approximately equal size; but frequently very small grains fit closely at the 

 point of union of two or more large grains; and there are also doublets, which consist of one large 

 and one very small component. 



The hiluni is often observed as a round or lenticular refractive spot, usually either slightly eccen- 

 tric or centric, but it may be eccentric to about one-third of the longitudinal axis. Frequently a short 

 transverse cleft (sometimes oblique) is found at the hilum. In the dome-shaped grains one longi- 

 tudinal fissure frequently runs from the sides of a small cavity at the hiliun. In the rounded forms 

 with slightly pointed distal end, one longitudinal fissure may proceed from the hilum or this fis- 

 sure may intersect a transverse fissure and a cross. Occa- 

 sionally either a Y-shaped or thorn-like cleft is present. 



The lamelloe are not demonstrable. 



The grains vary in size; the smaller are 3 by 2^; the 

 larger are 22 by 18ju in length and breadth; the common 

 size is 12 by llfi in length and breadth. The larger grains 

 and those of common size are usually separated parts of 

 aggregates, but occasionally round or nearly round grains 

 which have never formed part of the aggregate are found, 

 the larger of which are 16 by I6/.1 to 18 by ll/x in length 

 and breadth; the common size of these is 12 by 12/u in 

 length and breadth. 



Polariscopic Properties. The figure is usually either 

 slightly eccentric or centric. Its fines are sometimes 

 rather thick, straight, and cross each other at right 

 angles, but more often they are not distinct throughout 

 the entire figure and frequently are bent or bisected. 

 Sometimes two or more figm-es are closely connected, 

 denoting the presence of aggregates. 



The degree of polanzation is fair to high. There 

 is a considerable variation in the different grains and also in any one aspect of a given grain. The 

 polarization in two or three quadrants is frequently quite high, while the remaining one or two will 

 be very low. 



With selenite the quadrants are usually not well defined, but occasionally they are quite clean- 

 cut. They are generally irregular in shape and unequal in size. The blue is more often pure, but 

 is impure in many grains, while the yellow is usually not pure throughout the entire quadrant. 

 The degree of purity sometimes differs in different quadrants of a given grain. 



Iodine Reactions. With 0.25 per cent I.ugol's solution the grains color a fairly deep blue-violet, 

 which becomes quite deep in a minute; with 0.125 per cent solution they color a very light violet 

 which deepens rapidly. After heating in water until the grains are gelatinized, the solution colors 

 a deep indigo-blue and the grains a lighter but deep indigo-blue on the addition of iodine. If the 

 solution is boiled for 2 minutes and then treated with iodine, the solution colors more deeply and 

 most of the grain-residues either a very light blue or not at all, while a few are bright indigo-blue. 

 With an excess of iodine the gelatinized grain-residues become a deep purple and the capsules usu- 

 ally a deep heliotrope and occasionally wine-red. 



Staining Reactions. With gentian violet the grains begin to stain at once and in 30 minutes are 

 lightly stained; some, usually the smaller, color more than others. 



With safranin the grains color very slightly immediately and in 30 minutes are stained light 

 to fair, some more deeply than others. 



Temperature Reaction. The temperature of gelatinization is 69 to 71 C, mean 70". 



Curve of Reaction-Intensities of Starch of Crocus susianus 

 (Cloth-of-Gold). 



