406 



STARCHES OF LEGUMINOS^. 



hour there is very Uttle if any further change. The phenomena of the reaction arc identical with 

 those observed when the grains arc treated with pyrogallic acid. The reaction is qualitatively 

 the same as that noted for the green peas. 



STARCH OF PISUM SATIVUM VAR. (THOMAS LAXTON). (Plate 9, figs. 49 and 50. Chart 47.) 



Histological Characteristics. — In fomi the grains are probably simple, although practically all 

 are divided into from four to nine parts, commonly five or six, by very deep, broad fissures which 

 reach to the outer margin of the grain. They very closely resemble the Eugenie pea in all respects. 

 In some cases the grains have split entirely into many pieces or part-grains. The grains are evi- 

 dently round, ovoid, and oval in type, though the Assuring causes the margin to have a fairly regular 

 scalloped appearance, the whole grain looking somewhat like a rosette and suggestive of aggregates 

 of distorted spherical grains. The parts of the broken grains are wedge-shaped, triangular, irregu- 

 larly quadrangular, and crescent-shaped. There are rarely grains of the bean type common to Vicia 

 and Phaseolus. The grains usually are not so thick as they are broad. 



No hila could be distinguished. 



No lamellce can be distinguished, except when the grains are treated, as with Purdy's solution, 

 and then they appear as rather coarse, regular lines, following the outline of the margin and broken 

 by the fissures. There are eight to nine on the larger grains. 



The grains vary in size from the smaller, which are 8 by 8fi, to the larger, which are 32 by 32)u. 

 The common size is 24 by 24/i. 



Polariscopic Properties. — The characteristics of the figure can not be satisfactorily determined, 

 owing to the confusion of its lines ^vith those of the fissures. In the few grains of the bean type 

 present the figure corresponds with the peculiarities de- 

 scribed under Vicia. 



The degree of polarization is low. It does not vary 

 much in different aspects of the same grain, but is lower 

 in some grains than in others. It is in general less than 

 that of the grains of the Eugenie peas. In the grains of 

 the bean type polarization is fairly high. 



With selenite there is no division into definite quad- 

 rants, but into small spaces of blue and of yellow not very 

 definitely defined and grouped in each case with others of 

 the same color. In some grains blue is the predominating 

 color, but the yellow usually predominates. The colors 

 are not pure. 



lodirie Reactions. — With 0.25 per cent Lugol's solu- 

 tion the grains all color a fairly light violet; with 0.125 

 per cent solution they color a lighter violet, and the 

 color deepens fairly rapidly. The color is not quite so 

 deep as in Eugenie peas. After heating in water until all 

 of the grains are completely gelatinized, the solution 

 colors a deep blue-green and the gelatinized grains a deep 

 purplish-blue on the addition of iodine. After boiling for 2 minutes the solution colors a very deep 

 indigo-blue and the grain-residues a bright, rather light blue. The gelatinized grains all color a deep 

 purplish-blue when an excess of iodine is added, and even when the grains are boiled for 5 minutes 

 the results are the same as for Eugenie peas, showing great resistance to breaking down and extru- 

 sion of the inner, less resistant starch from the capsule. 



Staining Reactions. — With gentian violet the grains when viewed in masses show a slight tint of 

 violet, the color being somewhat deeper along the course of the stellate fissure. After remaining in the 

 solution for 30 minutes they are still very lightly stained. The color is the same as in Eugenie peas. 



With safranin the grains are slightly stained at once, the color being deeper along the course 

 of the stellate fissure. After remaining in the solution for 30 minutes they are still only very lightly 

 stained. The color is the same as in Eugenie peas. 



Temperature Reaction. — The temperature of gelatinization is 72.5° to 74° C, mean 73.25°. 



Effects of Various Reagents. — With chloral hydrate-iodine the grains begin to react at once. A 

 few are gelatinized in a minute, the majority in 2 minutes, and all in 5 minutes, except about 1 in 



Curve of Reaction-Intensities of Starch of Pisum 

 sativum var. (Thomas Laxton). 



