GENUS PHASEOLUS. 



387 



PCP3 



5 



The hila are almost. invariaMy oliscured or absent because of fissures and cavities. In most 

 of the sraiiis thcTC is a largo, ragp^ed, mesial fissure which extends the length of the grain, from which 

 short, irregular, side fissures extend. Tlu- hiluni is centric in the small unfi.ssurcd grains. 



The lamella arc usually fairly distinct, rather fine, continuous rings which follow closely the 

 outline of the grain. There are 8 to 12 on the larger grains. 



The grains vary in size from the smaller, which are 8 by S/x, to the larger, which are 16 by 30^ 

 or 40 by 30n in length and breadth. The common sizes are 30 by 24ju and 34 by 26/i in length and 

 breadth. 



Polariscopic Properties. The figure is centric or slightly eccentric, distinct, and usually clear-cut. 

 In the unfissured grains it consists of a single central line bisected at each end. In the other grains 

 the figure is confused by the fissures. The lines composing the figure are usually broad and regular. 



The degree of polarizalioti is high, not varying much in difTerent aspects of the same grain. 



With seknile tlie quadrants arc well defined, commonlj- irregular in form, unequal in size, and 

 sometimes subdivided. The colors are generally pure. 



Iodine Reactions. With 0.25 per cent Lugol's solution the grains all color a fairly deep blue 

 to a pinkish-violet; with 0.12.5 per cent solution they color fairly. After heating in water until all 

 the grains are completely gelatinized, the solution and the 



gelatinized grains color deeph' on the addition of iodine. Chart No. 36. 



After boiling for 2 minutes, the solution colors very deeplj' 

 and the grain-residues fairly. The capsules all color violet 

 or pinkish-violet with an excess of iodine. 



Staining Reactions. With gentian violet and with saf- 

 ranin the grains all begin to stain very lightly at once 

 antl in 30 minutes they arc lightly stained. 



Teinperatnre Reaction. The tenii)erature of gelatin- 

 ization is 74 to 75 C, mean 74.5. 



Effects of Various Reagents. With chloral hydrate- 

 iodine a few grains begin to react in 20 seconds. About 

 one-tenth are completely gelatinized in 5 minutes, one- 

 fifth in 30 minutes, and two-fifths in an hour. The effects 

 are the same qualitatively as in Vicia. 



With chromic acid some grains begin to react in 15 

 seconds and are dissolved in a minute. Most of them 

 begin to react in from 1 to 2V2 minutes and all are dis- 

 solved in 8 minutes. The effects are qualitatively the 

 same as in Vicia. 



The reaction with prjrogallic acid begins in a minute and is over in 5 minutes. The effects 

 are qualitatively the same as in Vicia. 



With /erne chloride a few grains begin to react in 2^ minutes and a very few are gelatinized in 

 30 minutes, with no further reaction in an hour. The reaction is qualitatively the same as in Vicia. 



The reaction with Purdy's solution begins in some in a minute and a few are partially gelatinized 

 in 20 minutes, with no further reaction in an hour. The effects are qualitatively the same as in Vicia. 



STARCH OF PHASEOLUS LUNATUS VAR. (HENDERSON'S BUSH LIMA BEAN). 



(Plate 6, figs. 33 and 34. Chart 37.) 



Histological Characteristics. In form the grains are simple and isolated. The surface is some- 

 times irregular, owing to rounded projections. The conspicuous forms are ovoid, oval, reniform 

 or bean-shapecl, elliptical, and round. There are also a few triangular and quadrangular grains 

 with rounded corners. The grains are about one-half to two-thirds as thick as they are broad. 



The hilum in most of the grains is obscured or absent, owing to fissures. In many grains the 

 fissuring is very irregular, but in the majority it consists of a single ragged fissure, which may bo 

 straight or bent, extending along the middle line to the margin and having a number of irregular 

 fissures branching from it. In small unfissured grains the hilum is centric. 



The lamellw are usually distinct, rather fine rings, which are discontinuous only when broken 

 by the fissures; they follow the outline of the grain. They are more distinct than in P. vulgaris. 

 There are about 8 to 12 on the larger gi-ains. 



Curve of Reaction-Intensities of Starch of 

 vulgaris var. (Red Kidney Bean). 



MINUTES 

 Phascolu3 



