GENUS IRIS. 



703 



The reaction with chromic acid begins in 20 seconds and is over in 2J/^ minutes. It is the same 

 qualitatively as that of the grains of /. florentina. 



Reaction with pyrogallic acid begins in 15 seconds and is over in 13^ minutes. It is the same 

 qualitatively as that of the grains of /. florentina. 



The reaction with ferric chloride begins in a minute. It is over in half in 10 minutes, in 

 nearly all in 17 minutes, and in all in 30 minutes. It is the same qualitatively as that of the 

 grains of /. florentina. 



The reaction with Purdy's solution begins in 15 seconds. Two-fifths of the grains are nearly 

 completely gelatinized and the remaining three-fifths are partially gelatinized in 15 minutes. The 

 reaction is the same qualitatively as that of the grains of /. florentina. 



STARCH OF IRIS CAUCASICA. (Plate 67, figs. 397 and 398. Chart 267.) 



Histological Characteristics. — In form the grains are usually simple. Compound grains fre- 

 quently occur. There are aggregates, separated-grains with pressure facets, and a few clumps con- 

 sisting chiefly of collections of minute grains. The surface of the grains is often irregular. The 

 irregularity is more frequently caused by small, rounded protuberances occurring at different points 

 on the margin of the grain. The causes of the irregularities noted under /. florentina are also found, 

 although the cup-shaped depression either at the end of the main grain or in the secondary growth is 

 not often observed. The conspicuous forms among the simple grains are irregular ovoid, elongated 

 oval with squared distal end, and round with squared distal end. Occasionally grains are globular 

 or conical with a rounded apex. The broadly lenticular 

 with rounded ends is frequently found among the com- 

 pound grains, as well as the irregular ovoid and the 

 double grain with the secondary growth already noted 

 under /. florentina. The aggregate grains often appear 

 in the form of one large grain having one or more small 

 ones at the side; or as three grains placed in a row. The 

 grains are not flattened, although irregular depressions 

 may be found on the surface. The grains are wider in 

 proportion to length, but the cup-shaped depression at 

 the distal end is not so marked as in /. florentina. 



The hilum may appear as a clear, distinct, round or 

 oval spot, centric in the globular forms, and slightly eccen- 

 tric to one-third, usually two-fifths, of the longitudinal axis 

 in the majority of the grains. There are sometimes 3, 4, or 

 as many as 7 hila in one grain. Either a cavity or clefts 

 of different forms are frequently located at the hilum. The 

 clefts are more often diagonal, sometimes two in the shape 



of a cross, and sometimes branched and root-like. Two Curve of Reaction-intensitiM of Starch of irU cauca.!ca. 

 short longitudinal lines frequently pass from the hilum. 



The lamellce in many grains are not distinct throughout the entire grain. They sometimes 

 form complete, regular rings or ellipses near the hilum and frequently have the shape of the outline, 

 even within a short distance of the hilum. There are about 20 rather coarse lamellse on the large 

 grains. 



The grains vary in size; the elongated grains are from 9 by 6/< to 49 by 34/i in length and 

 breadth; and the broader grains are 26 by 40^1 in length and breadth. The common size is 26 by 

 20/i in length and breadth. 



Polariscopic Properties. — The flgure is usually eccentric and distinct. The lines are rather 

 thick and often straight with broadening at the margin of the grain. They may be bent or bisected. 

 The figure is fairly clear-cut, more distinct, and less irregular than in the grains of /. florentina. 



The degree of polarization is high to very high, frequently varying in the same aspect of a given 

 grain. It is distinctly higher than in I. florentina. 



With selenite the quadrants are fairly well defined. The colors are quite pure in most of the 

 grains, and on the whole purer than in I. florentina. 



Iodine Reactions. — ^With 0.25 per cent Lugol's solution the grains all color a deep indigo-blue; 

 with 0.125 per cent solution they color fairly, and the color deepens rather rapidly. It is more than 



