OBNtrS IRIS. 



695 



STARCH OF IRIS XIPHIUM VAR. GRAND TRESORIER. (Plate 64, figs. 383 and 384. Chart 260.) 



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

 gates, separated-grains with pressure facets, and a few small clumps are present, as in /. fiorenlina. 

 The surface is sometimes irregular, owing to the causes noted under /. florentina. The conspicuous 

 forms in the simple grains are cone-shaped with rounded apex, ovoid with squared distal end, and 

 clam-shell-shaped; also quite perfect ovoid, laterally curved club-shaped, and oval forms. The 

 compound grains and aggregates are similar to those observed in I. florentina, except that a minute 

 globular grain is more frequently found at the lines of union of the component of compounds and 

 aggregates. The grains are broader in proportion to length and more irregular in outline than those 

 of /. florentina. 



The hilum is a distinct, round, clear spot, centric in the small globular forms and eccentric 

 two-fifths to one-third, usually two-fifths, of the longitudinal axis in the larger grains. Either a 

 cavity of the same shape as the hilum or irregular ragged clefts may be located at the hilum. The 

 clefts are more often arranged in a double, branched, root-like form, an irregular cross, or resem- 

 bling the outline of the flying bird or dragon-fly. In 

 the last-named shapes the clefts are usually diagonal to 

 the longitudinal axis. 



The lamellce are very indistinct and the number on a 

 grain can not be determined. Those occasionally visible 

 are rather coarse. 



The size of the average round form is 4 by 4/i, and 

 of the elongated forms from 6 by 3;u to 36 by 24)u in 

 length and breadth. The common size is 24 by 16/« in 

 length and breadth. 



Polariscopic Properties. — The figure is usually eccen- 

 tric and distinct. The lines are rather thick and some- 

 times broaden at the margin of the grain. They may 

 be straight, but are more often bent, and occasionally 

 bisected. The figure is fairly clear-cut, and rather more 

 distinct and regular than in /. florentina. 



The degree of polarization is rather high to quite high. 

 There is some variation in the different grains and occa- 

 sionally in the same aspect of a given grain. It is dis- 

 tinctly higher than in /. florentina. 



With selenite the quadrants are generally somewhat irregular in shape and unequal in size. 

 The colors are generally pure, the yellow sometimes being not quite pure. They are purer than in 

 I. florentina. 



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

 violet; with 0.125 per cent solution they all color lightly at once and the color does not deepen 

 rapidly. It is slightly more than that of the grains of I. 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 red-violet with an excess of iodine. 



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

 are lightly stained, more than the grains of /. florentina. 



With safranin the grains begin to stain at once and in 30 minutes they are fairly stained, more 

 than the grains of /. florentina. 



Temperature Reaction. — The temperature of gelatinization is 65° to 66° C, mean 65.5°. 



Effects of Various Reagents. — With choral hydrate-iodine the reaction begins in 45 seconds, is 

 over in two-thirds of the grains in 8 minutes, and in practically all in 15 minutes. It is the same 

 qualitatively as that of the grains of /. florentina. 



Reaction with chromic acid begins in some grains at once, in all in 15 seconds, and is over in a 

 minute. It is the same qualitatively as that of the grains of I. florentina. 



With pyrogallic acid the reaction begins in some grains at once, in all in 15 seconds, and is 

 over in 45 seconds. It is the same quahtatively as that of the grains of /. florentina. 

 46 



Curve of Reaction-Intensities of Starch of Iris xiphitim 

 var. Grand Tresorier. 



