696 



STARCHES OF IRIDACE^. 



The reaction with fcrrric chloride begins in a few grains in 30 seconds and is over in all in 12 

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



Reaction with Purdy's solution begins in a few grains in a minute, and in 5 minutes a few are 

 nearly completely gelatinized. All show signs of reacting and about one-fifth are nearly completely 

 gelatinized in 25 minutes. The reaction is qualitatively the same as that of the grains of /. florentina. 



STARCH OF IRIS XIPHIUM VAR. WILHELMINE. (Plate 65, figs. 385 and 386. Chart 261.) 



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

 gates, separated-grains with pressure facets, and a few pseudo aggregates (chiefly collections of 

 minute grains) are present as in /. florentina. The surface of the grains is occasionally irregular, 

 owing to the same causes as noted under I. florentina. The secondary set of lamellae is more fre- 

 quently formed at the proximal end in this species. The conspicuous forms of the simple grains 

 are the ovoid with a square distal end, oval, broadly triangular with curved base and roxmded angles, 

 pyriform, and a number of small, globular grains. The conspicuous forms of the compound grains 

 are irregular oval to heart-shaped. Those of the aggre- 

 gates are one minute globular grain closely fitted into a 

 cavity of one large grain, and two grains of equal size 

 with a small globular grain fitted in the depression at their 

 point of union. The broadly triangular forms are some- 

 what flattened. The grains are much broader in propor- 

 tion to the length and more regular than in /. florentina. 



The hilum is a distinct, clear, refractive 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. More than one hilum may he found 

 in a grain. There is usually at the hilum either a deep 

 cavity or ragged clefts, so arranged as to form a diagonal 

 cross approaching the figure of a flying ])ird or dragon-fly 

 when seen from below. 



The lamellce are usually invisible, bat occasionally 

 a few can be observed which generally are fairly coarse. 

 One or two distinct lamellae, either at about a third or half 

 the distance between the hilum and distal end, may some- 

 times be observed. In small globular forms the lamellae 



form complete rings around the hilum; but in grains in which the hihmi is dccplj^ fissured the 

 lamelke are not visible near this part and those observed usually assume the shape of the grain. 



The grains vary in size; the smaller are 4 by 4/u; the larger are 34 by 22yu and 34 by 28yu in length 

 and breadth. The common sizes are 26 by 20m and 26 by 24/i in length and breadth. 



Polariscopic Properties. The figure is generally eccentric and quite distinct. Its lines are 

 rather thick and usually straight with broadening towards the margin, l)ut are occasionally bent. 

 It is fairly regular and rather more clear-cut than that of /. florentina. 



The degree of -polarization is high to quite high, often varying in the same aspect of a given 

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



With selenite the quadrants are well defined and generally irregular in shape and unequal in 

 size. The colors are commonly pure, but the yellow in some grains is not quite pure. The colors 

 are rather purer than in /. 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 color fairly antl the color is deeper than that of the grains 

 of /. florentina. After heating in water until the grains are completelj' 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 cap- 

 sules all color a red-violet with an excess of iodine. 



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

 are lightly colored, and the tint is deeper than that of the grains of /. florentina. 



With safranin the grains begin to color at once and in 30 minutes are fairly stained and the 

 tint is deeper than that of the grains of /. florentina. 



Curve of Reaction-Intensities of Starch of Iria xiphium 

 var. Wilhelmine. 



