388 



STARCHES OF LEGUMINOS^. 



The grains vaiy in size from the smaller, which arc 8 by 8/.1, to the larger, which are 

 48 by 34/^ and 42 by 27fi in length and breadth. The common size is 30 by 20/i in length and 

 breadth. 



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

 cut. It appears generally to consist of a single mesial line which is l)isected at each end. Some of 

 the grains show what appears to be a confusion of figures, probably caused by the fissures. The 

 lines composing the figures are broad, clear-cut, sometimes bent and otherwise irregular. 



The degree of polarization is high and does not vary much in different aspects of the same 

 grain. It is slightly less than in P. vulgaris. 



With selenite the quadrants are, as a rule, well defined, irregular in form, unequal in size, and 

 sometimes subdivided. The colors are commonly pure. 



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

 to a pinkish-violet; with 0.125 per cent solution they all color fairly. The color is slightly less than 

 in P. vulgaris. After heating in water until all the grains 

 are completely gelatinized, the solution and the gelatin- 

 ized grains color deeply on the addition of iodine. After 

 boiling for 2 minutes the solution colors very deeply and 

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

 with an excess of iodine. 



Staining Reactions. VfWh gentian violet and safranin 

 the grains begin to stain very lightly at once and in 30 

 minutes are very lightly stained, slightly less than in 

 P. vulgaris. 



Temperature Reaction. The temperature of gelatin- 

 ization is 79 to 80.5 C, mean 79.75. 



Effects of Various Reagents. With chloral hydrate- 

 iodine a few small grains begin to react in 30 seconds. 

 About one-fifth of the total number are completely gela- 

 tinized in 10 minutes, two-fifths in 30 minutes, and one- 

 half in an hour. The reaction is qualitatively the same 

 as in Vicia. 



With chromic acid some grains begin to react in 30 

 seconds and are completely dissolved in 2 minutes. The 



other grains begin to react in 1 to 2 minutes, and the reaction is over in all in 8 minutes, 

 reaction is qualitatively the same as in Vicia. 



The reaction with pyrogallic acid begins in most grains in a miimte and is over in 4 minutes. 

 The reaction is qualitatively the same as in Vicia. 



The reaction begins in a few grains in 2 minutes with ferric chloride, and a few are gelatinized 

 in 5 minutes, about one-fifth in 25 minutes, and one-third in 50 minutes, with no further reaction 

 in an hour. The reaction is qualitatively the same as in Vicia. 



With Purdy's solution some grains begin to react in a minute. About one-sixth are nearly 

 completely gelatinized in 15 minutes and about one-fourth in 45 minutes, with no further reaction. 

 The reaction is qualitatively the same as in Vicia. 



Curve of Reaction-Intensities of Starch of Phaseolus 

 lunatus var. (Henderson's Bush Lima Bean). 



The 



Differentiation of Certain Starches of the Genus Phaseolus. 



HiSTOiiOaicAL Characteristics. 

 Conspicuous Forms. 



P. vulgaris: Simple, usually isolated, often somewhat 

 irregular. Ovoid, oval, elliptical, reniform, and 

 round. 



P. lunalus: Same as in P. vulgaris. 



Hilum Form, Number, and Position. 



P. vulgaris: Usually obscured by irregular fissures. Posi- 

 tion centric or slightly eccentric. 



P. lunatus: Same as in P. vulgaris. Position centric or 

 slightly eccentric. 



Histological Characteristics. Continued . 

 Lanietlfe General Characteristics and Number. 



P. vulgaris: Fairly distinct, rather fine, continuous rings, 

 following the outline of the grain. 8 to 12 on the 

 larger grains. 



P. lunatus: Same as in P. vulgaris, but more distinct. 8 to 

 12 on the larger grains. 



Size. 



P. vulgaris: From 8 to 46m, commonly 30m. 

 P. lunatus: From 8 to 48m, commonly 30m. 



