726 



STARCHES OP IRIDACE^. 



Chart No. 279. 



P I GV T 

 S 



value. The reactions have a very close correspondence, the most noticeable differences being in the 

 dark area in the polarization figure, and the anihne reactions, the reactions of W. meriana falling 

 below the other two, but the variations are unimportant. 



GENUS TRITONIA (MONTBRETIA). 



Tritonia includes over 30 species of South African bulbous plants, only a few of which are in 

 general cultivation. The older generic name is Montbretia, and tritonias are commonly known by 

 this name. The starches of 3 species, 2 varieties, and a hybrid were studied: T. crocata Ker-Gawl. 

 (Jxia crocata), T. crocata var. lilacina Hort., T. crocata var. rosea Hort., T. securigera Ker-Gawl., 

 T. potlsii Benth. (Montbretia pottsii Baker) and the hybrid T. crocosmceflora Lemoine (T. pottsii X 

 crocosmia aurea). 



STARCH OF TRITONIA CROCATA. (Plate 71, figs. 421 and 422. Chart 279.) 



Histological Characteristics. — In form the grains are mostly or solely simple and isolated, with 

 the exception of numerous aggregates (possibly some compounds), in the form of doublets and trip- 

 lets. There are a number of doublets which consist of one large grain into which a small grain of 

 variable size is partially embedded, giving the large grain the appearance of a nodular protrusion. 

 There are a few clumps consisting of smaller grains. A few grains have pressure facets, and the 

 facets may be shallow depressions, and hexagonal or 

 honeycomb-like; the siu-face is, as a rule, rounded and 

 regular. The most conspicuous forms of the isolated 

 grains are spherical, and transitional shapes between this 

 and ovoid and elliptical. The aggregates are most com- 

 monly triplets of rounded triangular form, some doublets 

 consisting of grains of approximately the same size and 

 from oval to flattened ovoid in form, and the large grains 

 with small grains partially embedded and of a broad, oval 

 form. The grains are not flattened in any diameter, and 

 hence as thick as wide. 



The hilum is indistinct, but when brought out by a 

 reagent, such as Purdy's solution, it is seen to be a small 

 round spot that is centric or very slightly eccentrically 

 placed. Rarely it is sUghtly fissured. There may be 2 

 or 3 or more hila according to the number of component 

 grains, and 2 or 3 hila may be observed in a simple grain. 



The lamellce are very indistinct unless rendered quite 

 evident by Purdy's solution or other reagent. They then 

 appear as fairly fine, regular, continuous rings. If there 

 is more than one hilum, each has usually its own set of lamellae, which fuse at a short distance from 

 the hilum or are inclosed by another set. In some cases the multiple hila are set close together in 

 a homogeneous, non-lamellated space, outlined by very distinct lamellae. There are about 10 

 lamella on a large grain. 



The grains vary in size from 3 to 26ix. The common size is IS/i. 



Polariscopic Properties. — The figure is centric, or slightly eccentric, distinct, but not as a rule 

 clear-cut. The lines are rather broad, without bending or other distortion. The figure may be 

 double or triple, in accordance with the number of hila. 



The degree of polarization is fair, with little variation in different grains or in different aspects 

 of the same grain. 



With selenite the quadrants are not as a rule sharply defined, but they tend to be regular in shape 

 and equal in size. The colors are fairly pure. 



Iodine Reactions. — With 0.25 per cent Lugol's solution the grains are colored fairly a blue- 

 violet at once and deepen rapidly; with 0.125 per cent solution they color lightly. After heating 

 in water until the grains are completely gelatinized, the solution is colored lightly and the grains 

 very deeply on the addition of iodine. After boiling for 2 minutes the solution and most of the 

 grain-residues are colored deeply. A few of the capsules which contain but little blue-reacting 

 starch become a violet color upon the addition of an excess of iodine. 



Curve of Reaction-Intensities of Starch of Tritonia 

 crocata. 



