702 



STARCHES OF IRIDACE^. 



Chart No. 266. 



I GV 

 S 



VH VD 50 



PS CI PA ( 

 " POPS 



STARCH OF IRIS ALATA. (Plate 66, figs. 395 and 396. Chart 266.) 



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

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

 sisting mainly of very small grains. The surface is often irregular, the irregularities being due to 

 the same causes noted in /. florentina. The conspicuous forms of the simple grains are elongated 

 ovoid with squared distal end, pyriform with squared distal end, oval with broadened distal end 

 which approaches the fresh-water mussel-shell-shaped, and numerous small globular grains. Slender, 

 finger-shaped forms similar to those of I. florentina are rare. The compound grains are frequently 

 either irregular ovoid, or there is one large grain with one or two minute globular grains at the 

 distal end. The irregular lenticular and the knob-shaped are rare. The aggregates consist usually 

 of one large grain having attached one or more small grains, or of two grains of equal size together 

 with minute globular grains at the point of union. The grains are much broader in relation to length, 

 and both compound grains and aggregates are more numerous than in 7. florentina. The grains 

 are not flattened. 



The hilum is a clear, distinct, round, refractive spot. In the elongated grains it is eccentric 

 two-fifths to one-fourth, usually one-third, of the longitudinal axis; 2 or 3 hila may be observed in 

 one grain. In place of the hilum either a cavity or clefts 

 of various forms may be seen, the most common forms 

 being one or two short, transverse clefts with a diagonal 

 cleft crossing them; one diagonal cleft with one trans- 

 verse cleft; and several short ones forming a stellate fig- 

 ure. Two longitudinal fissures frequently proceed from 

 the hilum or cleft at this point. 



The lamellw are rather coarse and fairly distinct. 

 They sometimes form complete regular rings around the 

 hilum, while in some grains they have at this part the form 

 of the margin of the grain. The lamellae are frequently 

 indistinct for one-third of the distance from the hilum, 

 while for the remaining distance they are well marked and 

 rather coarse. There are often 9 coarse lamellas in the 

 round grains of fair size, while 25 are sometimes visible 

 in the grains of elongated oval with squared-end form. 



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

 larger are 48 by 36/ and 50 by 32/i in length and breadth. 

 The common sizes are 32 by 22fi and 30 by 29ti in length 

 and breadth. 



Polariscopic Properties. The flgure is usually eccentric and quite distinct. Its lines are gen- 

 erally straight and fairly thick, broadening towards the margin of the grain; they may be bent or 

 bisected. The figure is fairly clear-cut and more distinct and less irregular than in /. florentina. 



The degree of polarization is high to very high. Occasionally it varies in the same aspect of 

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



With selenite the quadrants are well defined, often regular in shape, and equal in size. The 

 colors are generally purer than in I. florentina. The yellow is occasionally not quite pure. 



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 fairly rapidly. It is deeper than 

 that of the grains of I. florentina. After heating in water until the grains are completely gelatin- 

 ized, the solution and the gelatinized grains color deeply on the addition of iodine. After boiling 

 for 2 minutes the solution colors very deeply, but most of the grain-residues do not color at all. The 

 capsules all color a reddish-violet with an excess of iodine. 



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

 and in 30 minutes they are fairly stained, and distinctly more than the grains of I. florentina. 



Temperature Reaction. The temperature of gelatinization is 66 to 67 C, mean 66.5. 



Effects of Various Reagents. With chloral hydrate-iodine reaction begins in most grains in 30 

 seconds. It is over in three-fifths in 15 minutes, and in nearly all in 30 minutes. It is the same 

 qualitatively as that of the grains of Z. florentina. 



Curve of Reaction-Intensities of Starch of Iris alata. 



