758 



STARCHES OF IRIDACE^. 



swells, the lamellae become sharply defined and striated, delicate fissures radiate from the hilum, 

 and gelatinization proceeds, accompanied with uniform swelling. The small and medium-sized 

 grains mth regular outline are the most resistant. The gelatinized grains are swollen, but retain 

 the general shape of the untreated grain. 



STARCH OF SPAEAXIS VAR. (ALBERTINE). (Plate 77, figs. 467 and 458. Chart 297.) 



Histological Characteristics. In form the grains are almost wholly simple. Compound grains 

 consisting of few components are present in small numbers. The simple grains are found as isolated 

 grains, usually with sharply defined pressure facets, in aggregates of few components, and in clumps. 

 Irregularities of the grains are sometimes found which are attributable to the same causes as noted 

 for <S'. grandijlora alba. The conspicuous forms are dome-shaped (sometimes with a pointed base), 

 hemispherical, and round or nearly round; also ovoid, pyriform, imperfect quadrangular, triangular, 

 ellipsoidal, etc., as in S. grandiflora alba. There is in this starch a larger proportion of rather large, 

 ovoid, pyriform, and broadly triangular forms than in iS. grandiflora alba. 



The hilum is sometimes distinct as a small, clear, roxmd spot, centric or eccentric to about one- 

 third to one-fifth of the longitudinal axis. A small cavity, from which two short fissures usually 

 proceed, is often found in the dome-shaped grains. A cavity at the hilum with two or more radiating 

 fissures is usually present in the rather large pjTiform and 

 broadly triangular grains. 



The lamellce are not often demonstrable. They are 

 not quite so distinct in as large a proportion of grains as 

 in S. grandiflora alba, but when observed are of the same 

 character and number. 



The size varies; the smaller grains are 3 by 2^; the 

 larger dome-shaped are 19 by 18;u in length and breadth. 

 A number of rather large, round, isolated grains are 20 by 

 20/i in length and breadth. The common size of the dome- 

 shaped grains is 14 by 13yu and of the round grains 13 by 13;u 

 in length and breadth. A few ellipsoidal grains are usually 

 about 24 by IS/x, but rarely 32 by 26/x. 



Polariscopic Properties. The figure is centric or ec- 

 centric. Its Unes are similar to those of S. grandiflora alba, 

 but are more often distinct throughout the entire length. 

 In a large proportion of grains the figiue is quite eccentric. 



The degree of polarization is fair to high. There is 

 the same variation in the different grains as noted for 

 (S. grandiflora alba, as well as in the same aspect of a given 

 grain. The proportion of grains in which the polarization is high is greater than in iS'. grandiflora 

 alba, and there is a smaller number of grains in which it varies in the same aspect of the grain. 



With selenite the quadrants are often not clearly defined and they are in much larger propor- 

 tion in S. grandiflora alba. They are often irregular in shape and unequal in size, but a greater 

 proportion are larger than in S. grandiflora alba. The purity of the colors is about the same as in 

 S. grandiflora alba. 



Iodine Reactions. With 0.25 per cent Lugol's solution the grains color a deep blue with a 

 reddish tint which deepens very rapidly. The tint is much deeper and changes more quickly than 

 in S. grandiflora alba. With 0.125 per cent solution the grains color a deep blue-violet which deepens 

 rapidly; it is deeper than in S. grandiflora alba. After heating in water until all the grains are gelat- 

 inized and then treating with iocUne, the solution colors a greenish-blue and most of the gi-ains a 

 deep purplish-blue, and the rare, rather large, ellipsoidal grains color a deep reddish-violet. The color 

 of solution and grains is about the same as S. grandiflora alba. The solution if boiled for 2 minutes 

 and then treated vfiih iodine colors a deep indigo-blue and the grain-residues a bright, lighter blue, 

 some with reddish tint, a deeper blue than S. grandiflora alba. With an excess of iodine the solution 

 becomes a deeper blue, the grain-residues a deep purple, and the capsules a deep heliotrope to a 

 deep old-rose and a wine-red. There are more capsules with redder tint than in S. grandiflora alba. 



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

 are lightly to fairly colored. The tint is deeper than in S. grandiflora alba. 



Curve of Reaction- Intensities of Starch of Sparaxis 

 var. (Albertine). 



