GENUS CASTANEA. 



431 



P I GV 



5 



PS CI P* CA 

 "^ PC P3 



Curve of Reaction-Intensities of Starch of Castanea 

 americana. 



The grains varj' in size from that of the smaller, which are 3 by 2p., to the larger, which are 

 usually 1-1 by 10^, rarely 10 by 12ju in length and breadth. The common size is about 9 by 6/t in 

 length and breadth. 



Polariscopic Properties. The figure is usually eccentric and not always distinct throughout. The 

 lines intersect at an oblique angle, are frequentl}' bent, and sometimes bisected. In some grains the 

 figure is in the form of an elongated line having bisected ends of the bean type. Occasionally the 

 figure is centric, and the lines intersect at right angles. 



The degree of polarization is fair to high, frequently 

 varying in the same aspect of a given grain, one quadrant 

 often being lower than the other three. 



With selenite the quadrants are, as a rule, fairly 

 well defined, usually unequal in size, and irregular in 

 shape. The colors are, on the whole, fairly pure; the 

 blue is generally pure, but the yellow is often slightly 

 impure. 



Iodine Reactions. With 0.25 per cent Lugol's solu- 

 tion the grains color a fairly deep blue-violet, which 

 becomes very deep in 2 minutes; with 0.125 per cent 

 solution the grains are colored a very light blue-violet 

 which becomes quite deep in 2 minutes. After heating in 

 water until the grains are completely gelatinized, the solu- 

 tion becomes a reddish-blue and the grains a deep blue with 

 reddish tint on the addition of iodine. When the grains 

 are boiled for 2 minutes and then treated with iodine, the 

 solution and the grain-residues assume a deep blue with 

 a reddish tint. With an excess of iodine the solution 

 and grain-residues become deeper in color, and the capsules color a deep heliotrope to a wine-red. 



Staining Reactions.- With gentian violet the grains do not stain at once, l)ut in 30 minutes 

 they are slightly colored. 



With sajranin the grains do not stain immediately and in 30 minutes there is only a trace of 

 color in some grains. 



Tetnperature Reactions. The temperature of gelatinization is 58.5 to 60 C, mean 59.25. 



Effects of Various Reagents. With chloral hydrate-iodine reaction Ijegins immetliately. A few 

 grains are gelatinized in 20 seconds, the majority in 40 seconds, and all but rare resistant grains in a 

 minute, gelatinization in these being complete within iK to 2 minutes. Occasionally either a dark 

 spot or ring appears at the hilum and rarely either a dark line or slit-like structure in the central 

 part of the grain. Gelatinization usually begins at the distal end and proceeds rapidly over the 

 grain, accompanied by uniform swelling. The ring and slit-like structure become irregular in out- 

 line and are finally obscured as gelatinization and the accompanying deep-blue coloration ad\'ance 

 towards this region. In the grains with excrescences, which frequently appear at either end, gelat- 

 inization starts at both ends and proceeds towards the mitldle until the entire grain is finally 

 involved. The old-rose color so often observed in this reaction precedes the deep-blue coloration 

 during gelatinization. The gelatinized grains are swollen, but retain the general shape of the un- 

 treated grain. They are of a deep reddish-blue color, usually Avith a lighter, elongated mesial line; 

 and excrescences if present are also of lighter tint. 



Reaction with chromic acid begins at once and all the grains are dissolved in 10 seconds, except 

 very rare resistant grains, which may take 20 seconds. The grains swell rapidly, gelatinization is 

 almost instantaneous, the capsule bursts, and all parts are dissolved. The reaction is so rapid that 

 details of the process can not be determined. 



The reaction with pyrogallic acid begins at once, and all but very rare resistant grains are gelat- 

 inized in 10 seconds, the latter being gelatinized in 15 to 20 seconds. The grains swell rapidly 

 and gelatinization is almost instantaneous, so that it is imj)ossible to ascertain the details of the 

 process. The grains are completely gelatinized, with the exception of the outermost layers, which 

 are nuich swollen and somewhat distorted, but retain the general shape of untreated grains. 



With ferric chloride the swelling begins in a few grains in 30 seconds. A small number are 

 gelatinized in a minute, the majority in 2 minutes, and all but a few resistant grains in 5 minutes. 



