414 STARCHES OF LEGUMINOS^. 



less resistant starch passes into a semifluid mass, whicli occupies the central part of the grain. The 

 more resistant starch forms a band at the margin which is l:)road and dense at the sides and rather 

 thin and not very dense at the ends. This band l^ecomes thinner and less dense, and finally dis- 

 solves at the ends. The semifluid mass within flows out and is completely dissolved, followed by 

 solution of the remaining portions of the band. 



The reaction with pyrogallic acid begins in all the grains in 30 seconds and is over in 7 minutes. 

 The hila or the fissures in the region of the hila liecome more distinct, and the less resistant starch 

 is changed into a semifluid, swollen mass whicli occupies the central part of the grain. The 

 more resistant starch forms a marginal band that is very broatl and dense at the sides, and 

 rather thin and not very dense at the ends. This starch also gradually becomes gelatinous. 

 The gelatinized grains are large and retain some of the original form. The capsules are often 

 WTinkled and crmnpled. 



Reaction with ferric chloride begins in some grains in 30 seconds and is over in 20 minutes. 

 The reaction originates at one or both ends of the gi-ain. The starch at these points becomes gela- 

 tinous and swells out irregularly', and the reaction proceeds over the whole grain until the opposite 

 end or the center is reached, when portions of ungelatinized starch are often split by fissures into 

 two or more pieces and are gelatinized independently of one another. This splitting off is probably 

 due to the great strain on the ungelatinized parts of the grain caused by the swelling and gelatiniza- 

 tion of the broken down portions. The gelatinized grains are large and do not retain much of 

 their original form. The capsule is often much wrinkled and folded. 



With Purdy's solution a few grains show some reaction in 3 minutes, and about half are gela- 

 tinized completely in 20 minutes. The reaction is incomplete at the end of an hour, and it has the 

 same appearance as that with pyrogallic acid. 



GENUS ARACHIS. 



Arachis is a small genus with 7 known species, all but one of which are natives of Brazil. A. 

 hypogcea is the best knowii and is now cultivated in many warm climates, especially in some of the 

 southern United States, and commonly known as the peanut or ground-nut. The seeds are rich 

 in a limpid oil and contain much starch. The specimen of the Virginia peanut which served as 

 our source of starch is jirobably an agricultural variety of A. Jiypogoea, known as the Jumbo peanut. 



STARCH OF ARACHIS HYPOG<EA (JUMBO PEANUT). (Plate 10, figs. 57 and 58. Chart 52.) 



Histological Characteristics. In for7n the grains are simple and usually isolated. Aggregates 

 are present which consist of two or more components not pressed so firmty together as in many 

 such masses observed in the starches from other sources, hence the separated components have not 

 clearly marked pressure facets, but merely slight flattening here and there. The aggregates may 

 be foimd as triplets or quadruplets, but more often they ajipear either in chains or irregular elongated 

 masses. The most conspicuous forms of the isolated grains are spherical and ovoid. Rarely rounded- 

 oval to elliptical grains are found, which somewhat resemble the more conspicuous grains of Vicia, 

 Phaseulus, etc. Dome-shaped and slightly triangular grains with rounded angles and incidental 

 forms are occasionally obsei'vetl. 



The hiluni frequently appears as a clear spot, centric or nearly centric, with sometimes one or 

 more fissures, or a rounded cavity, at this point. When two fissures are present they may form a 

 cross; and if several, they are usually arranged as a stellate figure. The rounded-oval to elliptical 

 forms usually have an elongated, central cleft, from which short, radiating fissures sometimes emerge, 

 this arrangement resembling that of tyjiical bean-type grains. 



The laniellw are usuallj' not distinct. In some grains to 8 rather fine, concentric rings were fount!. 



The spherical grains vary in size from G to 18//, the common size being 12fi. The rounded oval 

 are commonly 10 by 12/i, and the elliptical forms commonly 8 by 12/i. 



Polariscopic Properties. The figure is centric or slightly eccentric and very distinct. The lines 

 are rather thin and usually straight; the figure is in the form of a cross. 



The degree of polarization is high, with some variation in the different grains. 



With selenite the quadrants are well defined, connnonly equal in size and regidar in shape. 

 The colors are pure. 



Iodine Reactions. With 0.2.5 per cent Lugol's solution the grains color a rather deep violet, 

 which deepens rather quickly, becoming a deep purple in 5 minutes; with 0.125 per cent solution 



