GENUS PISUM. 



403 



Qart No. 43. 



PS CI PA CA 

 ~ PCPS 



6 1 



gpnrrally five or six, which give the round, ovoid, and oval forms a rosettc-Iikc appearance. Some 

 of tiic linear forms are af^gi'CRates of the round and oval forms. Extension of the fissuration sepa- 

 rates these grains into i)art-grains, which are generally somewhat triangular, quadrangular, crcs- 

 centic, or hemispherical in form. Whether or not these part-grains are individual grains and 

 therefore parts of grains that are aggregates could not be determined in the normal grains because 

 of an absence of hila and lamella^, but by means of Purdy's solution lamella; were demonstrated 

 in the part-grains to be discontinuous lines, indicating that these part-grains are broken-off com- 

 ponents of primary grains. There are a few grains resembling those of Vicia, Phaseolus, and Lathy- 

 rus, but with these exceptions they are quite unlike the bean starches. The marked dissimilarity 

 may, however, be more apparent than real, since it may be due to peculiarities of Assuring, although 

 the histological differentiation is borne out by the results of the other methods of study. In some 

 of the grains of reniform shape there was a long longitudinal fissure, with deep lateral branches, 

 almost entirely separating the several parts of the grain from one another. The fissuration of the 

 round, ovoid, and oval types is merely a modification of this. 



No hila arc demonstrable. 



There are no lameUce visible in normal grains. When treated with Purdy's solution, lamellae 

 appear as discontinuous lines on each of the part-grains, showing that these part-grains are seg- 

 ments of the normal simple grains. They are regular, 

 rather coarse, and have the outline of the margin. There 

 are about 6 or 7 on the larger part-grains. 



The grains vary in size, from the part-grains, which 

 are 10 by 10;u, to the larger rounded grains, which are 38 

 by 38ju, and the larger oval grains, which are 44 by 32/i 

 in length and breadth. The common size is 28 by 28/i. 



Polariacopic Properties. — No definite figure can be 

 made out. The oval and round forms show a large dark 

 area with usually a half dozen or more short, radial lines 

 which border small bright spots. The part-grains appear 

 as bright spots without a figure. 



The degree of polarization is low. It does not vary 

 much in different grains, but in most of the grains it is 

 obscured or largely obliterated by the deep fissuration. 

 In the grains of the bean type it is fairly high. It does 

 not vary much in different aspects of the same grain. 



With selenite there is no definite division into quad- 

 rants, but spaces of blue and of yellow may be seen 

 which are not very definitely outlined and which are 

 grouped with others of the same color. Sometimes the blue and sometimes the yellow spaces pre- 

 dominate, according to the position of the grains in the field. The colors are not pure. 



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

 violet; with 0.125 per cent solution they color a lighter violet and the color deepens fairly rapidly. 

 After heating in water until all the grains are completely gelatinized, the solution is colored a deep 

 blue-green and the gelatinized grains a deep bluish-purple on the addition of iodine. After boiling 

 for 2 minutes, the solution colors a very deep indigo-blue and the grain-residues a deep purplish- 

 blue, the latter coloring a dark reddish-purple when an excess of iodine is added. The grain-residues 

 were again boiled for 5 minutes, and even then the capsules nearly always contained some gelatinized 

 starch which on addition of iodine became a deep-purple. Very rarely grains are seen which resem- 

 ble those of Laihyrus odoratus var. shahzada, and the capsules of these grains stain a reddish-violet. 



Staining Reactions. — The grains when viewed in masses show with gentian violet a slight tint 

 of violet at once; with safranin, a slight tint of red at once. After remaining in the solution 30 

 minutes they are very lightly stained. The color of the grain is not uniform in tint and usually 

 deeper along the course of the fissures. 



Temperature Reaction. — The temperature of gelatinization is 73° to 74° C, mean 73.5°. 



Effects of Various Reagents. — With chloral hydrate-iodine a few grains take on a deep indigo- 

 blue color immediately. The majority are gelatinized in 2 minutes and all but about 1 in 200 in 

 5 minutes; after an hour a few are still not gelatinized; these are the grains of the bean type. They 



Curve of Reaction-Intensities of Starch of Ptsum 

 sativum var. (Eugenie, green). 



