GENERA MUCUNA AND LENS. 



393 



grains is gelatinized. In an hour there is Httle if any progress in the reaction. The hihim, or cleft 

 at thi.s region, at the outstart of the reaction begins to swell, and if not already present, two large, 

 longitudinal, branched fissures are formed which pass obliquely from the hilum or cleft to the distal 

 margin. The lamella; become very sharply defined and striated and delicate lines pass from the 

 distal end towards the hilum. The grains in which the fissures are not very dark gelatinize more 

 quickly. Rarely a grain gelatinizes partially quite rapidly, and a number of refractive particles 

 become apparent during the process. The gelatinized grains are usually not much swollen, and 

 only a limited area becomes gelatinized. Very rarely in an hour gelatinized grains are observed 

 which are much swollen and almost all of the starch has been gelatinized, but it is quite probable 

 that such grains were partially gelatinized by the heat of grinding before treatment with the reagent. 



GENUS LENS. 



The small genus Lens, which according to some botanists comprises only 2 species and accord- 

 ing to others 8, is native to the region of the Mediterranean and the Orient, and has been placed 

 by Bentham and Hooker between Vicia and Lathyrus. The species L. esculenta is one of the oldest- 

 known plants cultivated by man for food purposes, and the seeds have an especial interest because 

 of their constituting the mess of pottage which figured in the sale of the birthright of Esau to Jacob. 

 The specimen from which we obtained the starch was an unknown variety in common cultivation. 



STARCH OF LENS ESCULENTA VAR. (Plate 7, figs. 37 and 38. Chart 40.) 



Histological Characteristics. — In form the grains are usually simple and they are isolated, except 

 a small nimiber which occur either in compound grains or in aggregates of few components. Some 

 of the grains are irregular in outline, which is chiefly due to one or more rounded elevations on 

 the surface. The conspicuous forms are ellipsoidal, rounded-oval, and reniform. There are some 

 ovoid, shield-shaped, heart-shaped, round, pyriform, and irregular grains of indefinite form. 



The hilum is usually obscured or destroyed by fissures, but rarely it may be observed as a clear 

 centric or slightly eccentric spot in the round grains of medium size and of elongated form in the 

 unfissured, elongated grains. There is commonly an elongated mesial, somewhat ragged cleft from 

 which frequently radiating fissures proceed. The cleft and fissures are generallj'^ very dark, but 

 often delicate and less opaque than the remainder of 

 the grain. Rarely an eccentric fissure may be observed 

 which intersects the main cleft either at a right or 

 slightly oblique angle. 



The lamellce are not demonstrable in the mesial part 

 of the grains, but over at least two-thirds of the grain 

 they are seen to be complete and coarse and to follow 

 closely the outline of the grain. On the elongated grains 

 there are from 8 to 14 lamellae and on the rounded 

 grains from 6 to 10. 



The grains vary in size from the smaller, which are 

 4 by 6;u, to the larger, which are 22 by 38/i in length and 

 breadth. The common size is 13 by 24/i in length and 

 breadth. 



Polariscopic Properties. — The figure may be in the 

 form of a cross or of the bean type (a mesial line with 

 bisected ends). It is centric or slightly eccentric. The 

 lines are thick and usually more or less ragged. 



The degree of polarization is high to very high, with 

 frequent variations in the same aspect of a given grain. 



With selenite the quadrants are not usually sharply defined, and are unequal in size and irreg- 

 ular in shape. The colors are pure. 



Iodine Reactions. — With 0.25 per cent Lugol's solution the grains color a very light violet with 

 a reddish tint, which in 5 minutes becomes a deep blue-violet; with 0.125 per cent solution they show 

 a slight trace of red-violet, which becomes deeper in 5 minutes. After heating in water until the 

 grains are gelatinized, both the solution and the grains color a deep indigo-blue on the addition of 

 iodine. After boiling for 2 minutes and then treating with iodine, the solution colors more deeply 



Chart No. 40. 



PS CI PA CA 

 ~ PC PS 



Curve of Reaction-Intensities of Starch of Lena 

 esculenta var. 



