690 



STARCHES OF IRIDACE^. 



I GV T P 

 S 



Chart No. 256. 



GV S T CI CA PA FC P S CLP_A CA 



PC PS 



s 



ularly. The starch at the proximal end also often becomes gelatinous and swells, and the process 

 advances inward from the two ends over the rest of the grain. In the other grains it simply advanced 

 upward and inward over the whole grain. The gelatinized grains are very large and thick-walled, 

 and the capsule is often folded and crumpled, and the grains distorted. 



The reaction with Purdy's solution begins in most grains in 30 seconds, and in all in a minute. 

 About half of the grains are partially gelatinized in 5 minutes, two-thirds in 10 minutes, nine-tenths 

 in 15 minutes, and completely in practically all in 30 minutes, except a small amount of starch at 

 the proximal end. The hilum or clefts at this region swell and two delicate fissures, if not already 

 present, form and extend obliquely from the hilum to the comers limiting the distal margin. The 

 lamellse between these two fissures become clearly defined; the grains gelatinize at the distal end and 

 the capsule spreads out laterally; gelatinization advances from the distal end towards the proximal 

 between the two fissures already noted, accompanied by swelling. In the grains with secondary 

 sets of lamellae a separate center of gelatinization is formed from that of the main body of the grain. 

 The gelatinized grains are swollen and sometimes refractive granules are embedded in the more 

 soluble starch. They retain the general shape of the untreated grain. 



STARCH OF IRIS PALLIDA VAR. SPECIOSA. (Plate 63, figs. 375 and 376. Chart 256.) 



Histological Characteristics. — In form the grains are usually simple and isolated. A few have 

 pressure facets. A number of grains are found in small aggregates and in compound grains of few 

 components, and a few clumps are present which consist usually of minute grains. The surface of 

 the grains is often irregular, owing to the same causes noted under /. florentina. The conspicuous 

 forms of the simple grains are the elongated ovoid, with a squared, hollowed distal end, oval ellip- 

 soidal, pure ovoid, pyriform, and nearly round. There are also dome-shaped with a well-marked 

 pressure facet, cone-shaped with rounded apex, spatula-shaped, and finger-shaped. As a result of 

 secondary deposits upon the primary grain, various shapes 

 are found such as noted for I. florentina. The compound 

 grains and aggregates are also of similar character to those 

 described for /. florentina. The grains are not so irreg- 

 ular in outline, and a larger proportion of the shortened, 

 broader forms are found than in /. florentina. 



The hilum is observed as either a distinct round or 

 elliptical spot, which is usually eccentric, the range of ec- 

 centricity being generally from one-fourth to one-eighth 

 of the longitudinal axis. The hilum is not as a rule fis- 

 sured. Occasionally either a diagonal or a transverse 

 cleft may pass through it. One short, delicate, longitudi- 

 nal fissm-e sometimes runs obliquely from each side of the 

 hilum. The hilum is less often fissured and not so 

 refractive when fissiu-ed as in /. florentina. 



The lamellce are not generally demonstrable through- 

 out the entire grain. Often they can not be observed at 

 the hilum, but occasionally they appear at this part as 

 indistinct, rather coarse, complete rings. Beyond this 

 region they tend to assume the shape and irregularity 

 of the grain, and are probably incomplete near the distal end. One or more secondary sets of 

 lamellae are observed at varying angles to the first set. Rarely 20 lamella; may be counted on the 

 larger grains. 



The grains vary in size; the smaller are 4 by 3m; the larger are 32 by 14/i in length and breadth. 

 The common size is 16 by 12/x in length and breadth. 



Polariscopic Properties. — The figure is usually eccentric. The proportion of grains of medium 

 size in which it is centric is much greater than in /. florentina. It is commonly clear-cut, and its 

 lines are similar in character to those described for /. florentina, but more often straight. 



The degree of polarization is fair to high. The same variations are found as noted for /. floren- 

 tina. Polarization is higher than in /. florentina. 



With selenite the quadrants are fairly well defined, but not quite so irregular in shape and so 

 unequal in size as in /. florentina, and the colors are more often pure than in /. florentina. 



Curve of Reaction-Intensities of Starch of Iris pallida 

 var. speciosa. 



