GENUS MU8A. 



773 



not show saccular projections from the proximal end. 

 the two ends gelatinize first, then the central part. 



Another method of reaction is one in which 



P I GV T P 

 S 



aartNo. 321. 



GV s T CI CA PA rc P S CI PA CA 



STARCH OF MUSA CAVENDISHII OBTAINED FROM THE GREEN FRUIT. 

 (Plate 79, figs. 471 and 472. Chart 321.) 



Histological Characteristics. — Inform the grains are simple, and they are isolated with the excep- 

 tion of a few clumps. No pressure facets were observed. Grains are much flattened and the margin is 

 generally more or less irregular, owing in part to depressions and rounded protuberances and nipple- 

 like projections, as in the case of the stalk starch. The conspicuous forms are the ovoid to the clam- 

 shell-shaped. There are also rounded triangular, straight or bent, elongated elliptical, elliptical, 

 rod-like, pyriform, and various irregular forms. The grains when seen from the end or edge appear 

 as more or less irregular, elongated ellipses. 



The hilum is not very distinct. It is a comparatively small, round, non-refractive spot, situated 

 generally very eccentrically, and may be in, but usually to one side, of the median line. It is never 

 fissured, and it may be elongated in a transverse direction. Several grains with double hila were 

 observed. 



The lamelloe are very distinct, fine rings about the hilum and rather irregular arcs of cu-cles 

 beyond. They are often wavy, or otherwise irregular in outline, owing to the deviations of the sur- 

 face. Those near the distal end are more distinct and not 

 so fine as those near the hilum. The average number on 

 fairly large grains is from 30 to 45. 



The grains vary in size from 6 to TO/i. The common 

 size is 35^1. 



Polariscopic Properties. — The figure is usually very 

 eccentric, fairly distinct, and not well defined. Its lines 

 are apt to be very broad and dim, and may be somewhat 

 bent or otherwise distorted. If the grain is viewed from 

 the end or edge the figure is very clear-cut and distinct. 



The degree of polarization is low, but distinctly 

 higher than that of the starch of the stalk. It is ab- 

 sent at some points, and very low throughout in some 

 grains, which may be accounted for in part by the thin- 

 ness of the grains. It is quite high when grains are viewed 

 from the end or edge; in other words, in accordance with 

 the thickness of the starch. 



With selenite the quadrants are not well defined, 

 very unequal in size, and irregular in shape. 



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

 tion the grains color immediately and deeply a bluish-violet; with 0.125 per cent solution they color 

 lightly immediately, but the color deepens rapidly. The color in both these reactions is deeper than 

 that shown by the stalk-starch. After heating in water until all the grains are completely gelatin- 

 ized, the solution is slightly colored on the addition of iodine and some grains are colored deeply 

 and others lightly. Some of the latter show a violet-colored capsule. After boiling for 2 minutes 

 the solution is much more deeply colored but the grain-residues much less deeply. With a very 

 slight excess of iodine the capsules are seen to be colored a blue-violet and are much wrinkled and 

 crumpled, but none are disintegrated. 



Staining Reactions. — With gentian violet the grains begin to stain at once. After 30 minutes 

 the color is fairly deep, deeper than that shown by the stalk-starch. 



With safranin staining begins at once rather lightly, but after 30 minutes it is fairly imiform. 

 There is no difference in the staining of the fruit-starch and the stalk-starch. 



Temperature Reaction. — The temperature of gelatinization is 66.5° to 68.5° C, mean 67.5°. 



Effects of Various Reagents. — With chloral hydrate-iodine reaction begins in most grains in a 

 minute. All are darkened in 6 minutes. The hilum becomes more prominent. The lamella? after 

 a preliminary clearing are not entirely obscured. Irregular points on the margin begin to darken, 

 usually at the distal end of sides. The points become joined, as the process spreads, and the hilum is 

 approached. The process may stop on one side of the hilum and then spread inward until the whole 



Curve of Reaction-Intensities of Starch of Musa 

 cavendishii (green fruit). 



