GENUS IRIS. 



693 



STARCH OF IRIS BISMARCKIANA. (Plate 64, figa. 379 and 380. Chart 258.) 



Histological Characteristics. In form the grains are mostly simple. There are some compound 

 grains, aggregates which are usually in the form of doublets or triplets, separated-grains with pressure 

 facets, and clumps chiefly consisting of very small grains. The surface of the grains is often irregular, 

 the irregularities of both the simple and the compound grains being due to the same causes as noted 

 under /. florentina. The conspicuous forms are with some exceptions the same as those observed 

 in /. florentina, but the grains give the impression of more broadness in relation to length, and 

 the conical grain with rounded apex is more frequently found. Among the compound grains a 

 broadly lenticular grain with rounded ends is frequently found besides the forms noted in /. 

 florentina. The small, globular grains sometimes attached to a very large grain are more often 

 at the side than fitting into the distal end, as observed in I. florentina, and the depression at this 

 end is not so deep as in /. florentina. The grains of I. bismarckiana more closely resemble those of 

 /. iberica than /. florentina. 



The hilum is a fairly distinct, refractive, round or lenticular spot, centric in the small round 

 grains, and eccentric one-fourth to one-seventh, usually one-sixth, of the longitudinal axis in the 

 larger elongated grains; 4 hila are sometimes present in a single grain. In place of the hilum there 

 is often a rounded cavity which is not often fissured. 



The lamellce are fairly distinct and may form com- 

 plete rings around the hilum. Beyond this area they 

 have the form of the outline of the grain, and show any 

 irregularities that may appear in it. The number on grains 

 of fair size varies from 10 to 16. 



The grains vary in size; the smaller are 4 by 4;u; the 

 larger are 26 by 14;u in length and breadth. The com- 

 mon size is 18 by 12ju in length and breadth. 



Polariscopic Properties. The figure is usually eccen- 

 tric and distinct. Its lines are rather fine and often bent, 

 bisected, or otherwise distorted. It is fairly clear-cut, but 

 more irregular than in I. florentina. 



The degree of polarization is fair to fairly high, with 

 frequent variations in the same aspect of a given grain. 

 It is slightly higher than in /. florentina. 



With selenite the quadrants are generally fairly well 

 defined, but usually irregular in shape and unequal in 

 The colors are fairly pLU'e, the blue being quite 



Size. 



Curve of Reaction-Intensities of Starch of Iris 

 bismarckiana. 



pure, but the yellow is often not pure. 



Iodine Reactions. With 0.25 per cent Lugol's solution the grains all color a fairly deep 

 violet; with 0.125 per cent solution they color lightly at first and the color does not deepen rapidly. 

 It is about the same as that of the grains of /. florentina. After heating in water until the 

 grains are completely gelatinized, the solution colors fairly deeply and the gelatinized grains very 

 deeply on the addition of iodine. After boiling for 2 minutes the solution colors very deeply, 

 but most of the grain-residues not at all. The capsules all color a deep red-violet with an excess 

 of iodine. 



Staining Reactions. With gentian violet and with safranin the grains begin to stain at once 

 and in 30 minutes they are lightly stained. The stain is the same as that of the grains of 

 /. florentina. 



Temperature Reaction. The temperature of gelatinization is 71 to 73 C, mean 72. 



Effects of Various Reagents. With chloral hydrate-iodine reaction begins in 15 seconds and is 

 over in 4 minutes. It is the same qualitatively as that of the grains of /. florentina. 



The reaction with chromic add begins in a few seconds and is over in 35 seconds. It is the same 

 qualitatively as that of the grains of /. florentina. 



The reaction with pxjrogallic acid begins in 7 seconds and is over in 70 seconds. It is the same 

 qualitatively as that of the grains of /. florentina. 



Reaction -with ferric chloride begins in 15 seconds and is over in 5 minutes. It is the same 

 qualitatively as that of the grains of /. florentina. 



