GENUS PISUM. 



407 



Chart No. 48. 



GV S T CI CA PA 



200, these being of the bean type. The latter are not gelatinized in an hour. The reaction is quali- 

 tatively the same as that noted for Eugenie peas. 



The grains begin to react at once with chromic acid, and all parts of the gi-ains are almost wholly 

 dissolved in 30 seconds and completely in 5 minutes. The reaction is qualitatively the same as for 

 Eugenie peas. 



Reaction with pyrogallic acid begins at once. In 5 minutes all the grains arc affected, but 

 there is little further change in an hour. The lamellse become very distinct and the fissures very 

 refractive. Verj' rarely a grain of the bean type is observed which is completely gelatinized, the 

 others are slightly affected. The reaction is qualitatively the same as that observed for Eugenie peas. 



With ferric chloride the grains begin to react in a minute. A few are gelatinized in 4 minutes, 

 the majority in 30 minutes, and nearly all in an hour. The reaction is qualitatively the same as 

 that observed for Eugenie peas. 



With Purdy's solution the reaction begins at once, the grains are swollen in 3K minutes, and 

 gelatinization is complete, except in the outermost lamella;, in 30 minutes. After remaining in the 

 solution for an hour the general shape of the normal grain is retained, but most of the lamelliB are 

 gelatinized, and there are many refractive granules of ungelat.inized starch. The reaction is quali- 

 tatively the same as that observed in Eugenie peas. 



STARCH OF PISUM SATIVUM VAR. (ELECTRIC EXTRA EARLY). (Plate 9, figs. 51 and 52. Chart 48.) 



Histological Characteristics. — In form the grains are simple and isolated, and there are no pres- 

 sure facets. The grains are frequently somewhat irregular in outline, owing usually to slight depres- 

 sions. The conspicuous forms are ovoid, oval, elliptical, and reniform. There are in addition round 

 to nearly roimd grains, and some incidental forms. The 

 grains are not so thick as they are broad. They corre- 

 spond in general characteristics with the bean type, as, 

 for instance, those of Vicia, Phaseolus, Lathyrus, etc. 



When an elongated form of grain is not fissured the 

 hilum may be regarded as represented by a granular, 

 non-lamellated space appearing in the middle, and in the 

 round or nearly round grains by a small, rather obscure 

 spot. When the grains are fissured this mesial space is 

 either not visible or is divided into many parts. 



The lamellae are very distinct, rather coarse, continu- 

 ous lines which follow the outline of the grain. There 

 are from 7 to 8 on the larger grains. 



The grains vary in size from the smaller, which are 

 6 by 6/1, to the larger elongated forms, which are 44 by 

 24/1 in length and breadth. The common size is 32 by 20/i 

 in length and breadth. 



Polariscopic Properties. — The figure is centric or 

 slightly eccentric, distinct, and in most cases fairly clear- 

 cut. In the unfissured grains it is of the bean type, hav- 

 ing the form of a single line extending down the middle of the grain, with each end bisected. When 

 fissures are present the figure is more or less broken up and distorted. Sometimes the lines or parts 

 of lines composing it are bisected and occasionally curved or bent. 



The degree of polarization is fairly high to high, not varying much in different aspects of a grain, 

 but sometimes less at some points than at others. It is much higher than that of Eugenie peas. 



With selenite the quadrants are fairly well defined, irregular in shape, and unequal in size. The 

 colors are usually pure. 



Iodine Reactions. — With 0.25 per cent Lugol's solution the majority of the grains color at once 

 a fair violet, which deepens gradually to a deep blue-violet; with 0.125 per cent solution they color 

 a very delicate violet, deeper than that of the grains of Eugenie peas. After heating in water until 

 the grains are completely gelatinized, the solution colors a deep blue-green and the grains a blue- 

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

 and the grain-residues a bright, light blue. The capsules all color a deep reddish-purple with an 

 excess of iodine. 

 28 



Curve of Reaction-Intensities of Starch of Pisum 

 sativum var. (EJectric Extra Early). 



