724 



STARCHES OF IRIDACE^. 



The hilum is distinct. When not fissured it is a comparatively large round spot, or a hollow 

 space centrally or somewhat eccentrically situated, and usually in the median line. It often is 

 fissured, and the fissuration may be a small, transverse, ragged line, 3-armed or stellate. Lines or 

 fissures at the junctions of the components of aggregates are quite common. 



The la7ncU(F are indistinct, and when distinguishable they appear as coarse, regular, concentric 

 rings, sometimes divided into segments by the fissures. They tend to follow closely the outline of 

 the margin. There are probably 5 to 6 on the larger grains. 



The small grains vary in size from 3 to 20ju, and the doublets to 34^. The common size of the 

 double grains is 22 by IS/i in length and breadth. 



Polar iscopic Properties. The fig^ire is usually eccentric, distinct, and generally clear-cut. Some- 

 times its lines become broader and less distinctly outlined near the margin. Double and multiple aggre- 

 gates show corresponding figures. The lines are sometimes slightly bent, but as a rule the figure is regular. 



The degree of polarization is high, slightly higher 

 than that of the grains of W. humilis. It varies some- Chari No. 278. 



what in different grains, but not much with the position 

 of the grains. A dark central area tends to be much less 

 marked in this species than in W. humilis, but more 

 marked than in W. iridifolia var o'brieni. 



With selenite the quadrants are fairly well defined, 

 fairly regular in shape, and fairly equal in size. The 

 colors are pure. 



Iodine Reactions. With 0.25 per cent Lugol's solu- 

 tion the grains color a very light violet and the color 

 deepens very slowly; with 0.125 per cent solution the 

 grains are scarcely colored at all, and the reaction is less 

 than that of the grains of W. humilis. After heating 

 until the grains are completely gelatinized, both the solu- 

 tion and the grains color deeply. On the addition of 

 iodine and after boiling 2 minutes the solution colors 

 more deeply and the grain-residues less. Most of the cap- 

 sules contain some blue-reacting starch and they color a 

 red-violet with slight excess of iodine. 



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

 are fairly stained. The color is not so deep as that of the grains of W. humilis. 



With safranin the grains begin to stain at once and after 30 minutes are lightly stained. The 

 color is not so deep as that of the grains of W. humilis. 



Temperature Reaction. The temperature of gelatinization is 75.5 to 77 C, mean 76.25. 



Effects of Various Reagents. With chlwal hydrate-iodine reaction begins in some of the very 

 small grains in 3 minutes and they are gelatinized in 5 minutes. Some medium-sized grains begin 

 to react within this time. All the small grains are gelatinized in 13 minutes and a few of the medium- 

 sized grains are gelatinized in 20 minutes. The larger grains, with few e-xceptions, remain unaffected. 

 The reaction is qualitatively the same as that of the grains of W. humilis. 



The reaction with chromic acid begins in the small grains in 30 seconds, and in the large grains 

 in a minute, and is over in all in 5 minutes. It is the same qualitatively as that of the grains of 

 W. humilis. 



Reaction with pyrogallic add begins in some small grains in 30 seconds and in all the grains 

 in \]/2 to 2 minutes. All are completely gelatinized in 15 minutes. This reaction is qualitatively 

 the same as that of the grains of W. humilis. 



With ferric chloride a few of the smaller grains begin to react in 2 minutes. In 15 minutes all 

 the small grains are gelatinized and half of the larger ones are affected and many completely gelat- 

 inized. About three-fourths of all the grains are gelatinized in 25 minutes, and four-fifths in 35 

 minutes. All are affected in 45 minutes, and in IJ/^ hours all are completely gelatinized, except a 

 very few near the edges of the cover-shp. This reaction is qualitatively the same as that of the 

 grains of W. humilis. 



With Pimhj's solution about half the grains are slightly affected in 3 minutes and all in 15 minutes. 

 There is no further change. This reaction is qualitatively the same as that of the grains of W. humilis. 



Curve of Reaction-Intensities of Starch of Watsonia 

 meriana. 



