GENUS SCILLA. 



641 



are never clear-cut with well-clefincd edges. If the grain is compound the components are usually 

 partially separated by fissures extending out to the rows of lamellae encircling the component grains. 

 The grains are rounded, except for some irregularities in the form of pressure facets and for small, 

 irregular protuberances due to the unequal development of the surface. The conspicuous form is 

 ovoid, which may be a pure ovoid or with the distal end flattened. There are also round, pyramidal, 

 triangular, and dome-shaped. Most of these forms are modifications of the ovoid by pressure facets. 

 The grains are not flattened in any diameter, except by pressure facets. 



The hilum is distinct and comparatively large. It is usually eccentric, about one-fourth to 

 one-third of the longitudinal diameter of the grain. In some grains it is centric. It may or may not 

 be in the median Une, usually it is round, except when marked by a fissure, but frequently it is 

 elongated or lenticular. In the compound grains there are 2 or more hila in accordance with the 

 number of grain-components, and in such cases each hilum has its separate set of lamellae, the 

 several sets as a rule being separated from one another by fissures. In other cases 2 hila may be 

 placed very close together in a non-lamellated space, and such hila may be termed double. The 

 hilum is often fissured, sometimes by a single line that may be straight or have a double curve 

 in the transverse, diagonal, or longitudinal axis of the grain; or there may be three lines radiating 

 from the hilum; or a cross; or an irregularly stellate arrangement of fissures. Most of the fissures 

 are clean-cut and not ragged. There is in the case of 

 compound grains quite a characteristic arrangement of 

 two or more small crosses of the same size side by side. 



The lamellce are distinct. They are rather coarse, 

 continuous, and regular; and coarser and more distinct 

 near the hilum than near the margin. In compound 

 grains each hilum is surrounded by about 2 or 3 lamellse, 

 the whole group of hila with their separate lamellse being 

 in turn inclosed by several continuous lamellae. There 

 are on an average 6 lamellae on the simple, isolated grains 

 and about 16 on the compound grains. 



The grains vary in size from 3 to 28/i. The common 

 size is 18ju. 



Polariscopic Properties. — The figure is usually eccen- 

 tric, generally clear-cut, and distinct. In some grains one 

 or more of the lines may be broader and less well defined 

 than the others, which is due undoubtedly in some cases 

 to differences in the degree of polarization of different 

 parts of the grain. The longer lines are sometimes slightly 

 bent or otherwise distorted, and they may vary much in width as well as in sharpness of outline. 



The degree of polarization is fairly high. It may be low in some parts of the grains and it varies 

 somewhat in different grains. 



With selenite the quadrants are usually fairly well defined, some very well, and they are usually 

 fairly regular in shape and unequal in size. The colors are fairly pure. 



Iodine Reactions. — With 0.25 per cent Lugol's solution the grains at once color deeply a blue- 

 violet; with 0.125 per cent solution the grains are colored lightly at once and become deeper slowly. 

 After heating until all the grains are completely gelatinized, the solution and the gelatinized grains 

 are colored deeply with iodine. Some of the grains do not color so deeply as the others. With an 

 excess of iodine the grains show a violet capsule. After boiling for 2 minutes the solution is colored 

 much more deeply, but the grain-residues much less. All of the capsules become of a violet color 

 and are found to contain some blue-reacting material upon adding an excess of iodine. 



Staining Reactions. — With gentian violet the grains begin to stain lightly in 30 seconds and after 

 30 minutes they are fairly colored. 



With safranin the grains begin to stain very slightly in a minute. After 30 minutes they are 

 fairly deeply stained. 



Temperature Reaction. — The temperature of gelatinization is 05° to 67° C, mean 66°. 



Effects of Various Reagents. — With chloral hydrate-iodine the grains begin to react in 30 seconds. 

 Almost all are gelatinized in 8 minutes and all in 15 miimtes. The reaction usually begins at the 

 distal end. The grain at this point becomes darker, then swells somewhat, with a Uttle irregular 



Curve of Reaction-Intensities of Starch of SciUa ubirica. 



