432 



STARCHES OP CXJPXJLIFERiE. 



which latter are nearly always completely gelatinized in 8 to 12 minutes; very rarely a grain may 

 resist gelatinization for 28 minutes. A narrow translucent border is formed around the entire grain, 

 which appears darker than the main bodj' of the grain, and a dark spot is observed at the hilum. 

 Gelatinization, accompanied by a rapid distension of the capsule, usually begins at the distal end, 

 followed quickly by gelatinization at the proximal end, then spreading around the margin of the 

 grain. The central part of the grain is the last to undergo gelatinization. When the process is 

 near completion the most resistant starch is broken into rather large fragments which are finally 

 gelatinized. These fragments do not fly asunder forcibly in grains in which gelatinization is rapid, 

 while they do in the resistant grains. The gelatinized grains are so much swollen and distorted 

 that they do not retain the shape of the untreated grain. 



Reaction with Purdy's sohUion begins at once and a few grains are gelatinized in 20 seconds. 

 About half are gelatinized in a minute, about four-fifths in 2 minutes, and all but a few resistant 

 grains in 3 minutes, the latter perhaps taking 5 minutes, rarely 10. The hilum, if demonstrable, 

 swells, and a single longitudinal cleft, which may have a few radial fissures, is formed, along which 

 gelatinization proceeds. When the gi-ain has one or more excrescences, a separate center of gelat- 

 inization is formed in each, and sometimes a partition persists between these and the main body 

 of the grain after the reaction is complete. The grains are completely gelatinized, except the 

 outermost layers, and are swollen, but the general shape of the untreated grain is retained. 



STARCH OF CASTANEA SATIVA VAR. NUMBO. (Plate 12, figs. 71 and 72. Chart 70.) 



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

 which occur in clumps and in small aggregates. There are a few compound grains, usually of two 

 or three components. A few isolated grains have well- 

 marked pressure facets. The irregularity of the surface 

 and the location and structure of the protuberances are 

 the same as in C. americana. The conspicuous forms are 

 imperfect bean-shaped, ellipsoidal, ovoid, club-shaped 

 with pointed distal end, and triangular with rounded 

 angles. There are some pyriform, napiform, dome- 

 shaped, lenticular, conical, finger-shaped, and irregular 

 grains of indefinite form. 



The hilum is not usually demonstrable, but occasion- 

 ally it may be observed as a round, fairly refractive spot, 

 which is occasionally centric, but usually two-fifths to 

 one-fifth eccentric of the longitudinal axis. A small irreg- 

 ular cavity, a diagonal, or a short transverse fissure is 

 occasionally foimd at the hilima. A rather deep, central 

 cleft is often noted in grains with excrescences at either 

 end. A single longitudinal fissure frequently proceeds 

 from the hilum. Fissures are more often present and arc 

 deeper than in the grains of Castanea americana. 



The lamelloe are not very distinct, but are more often 

 demonstrable than in grains of C. americana. They have the same structure and character as in C. 

 americana. Occasionally 8 to 10 may be counted on the larger grains. 



The grains vary in size from the smaller, which are 3 by 2^, to the larger, which are 22 by 12ju, 

 rarely 30 by 12/t, in length and breadth. The common size is 14 by S/j. in length and breadth. 



Polariscopic Properties. — ^The figures are the same as in C. americana. The proportion of grains 

 in which the figure is of the bean type, consisting of an elongated line with bisected ends, is greater 

 than in C. americana. 



The degree of polarization is fair to quite high, but sometimes varying in the same aspect of 

 a given grain. The proportion of grains in which polarization is high is greater than in C. americana. 



With selenite the quadrants are well defined and are more clear-cut than in C. americana; 

 usually unequal in size and irregular in shape. The colors are generally pure; more often pure than 

 in the grains of C. americana. 



Iodine Reactions. — With 0.25 per cent Ivugol's solution the grains color a fairly deep blue- 

 violet, which deepens rapidly; with 0.125 per cent solution they color a very light blue-violet, which 



Curve of Reaction-Intensities of Starch of Castanea 

 sativa var. numbo. 



