GENUS DIEFFENBACHIA. 



459 



or a more or less close approach to this form. As some of the grains, such as the T, boot, and 

 allied forms, consist of two or more distinct parts, the figure may be peculiarly modified. 



The degree of polarization is very high, much higher than in D. seguine var. nobilis, varying 

 according to the aspect of the grain seen, and also in different grains. 



With selenite the quadrants are well defined, irregular in shape, and of unequal size. In the 

 grains with secondary and tertiary deposits the quadrants are of peculiar shapes according to the 

 modifications in form. The colors are pure. 



Iodine Reactions. — -With 0.25 per cent Lugol's solution the grains are colored deeply a blue- 

 violet; with 0.125 per cent solution the grains are colored fairly deep. In both reactions the color 

 is deeper than in the grains of D. seguine var. nobilis. After heating until the grains are completely 

 gelatinized, the solution colors an indigo and the grains 

 variably, some deeply and others lightly, with iodine. 

 The grains are large, somewhat distorted, but retain to 

 some extent their original shapes. After boiling for 2 

 minutes, the solution is colored more deeply, but the 

 grain-residues not at all, or a very faint blue. With ex- 

 cess of iodine the capsules color red. Many of the grains 

 are reduced to granular masses or are partly dissolved. 



Staining Reactions. — With gentian violet and with 

 safranin the grains begin to stain in a minute and after 

 30 minutes are stained deeply — more deeply than the 

 grains of D. seguine var. nobilis. 



Temperature Reaction. — The temperature of gelatini- 

 zation is 70° to 71° C, mean 70.5°. 



Effects of Various Reagents. — -With chloral hydrate- 

 iodine (piate 19, figs. 113 and 114) the reaction begins in 

 2 minutes. About half are darkened and gelatinized in 

 30 minutes, and all but one-sixth in an hour. The hilum 

 becomes distinct as a black spot, or if fissured it appears 

 in the form of irregular bubbles. The lamelliE become 

 distinct. The grains have at first a light violet tint which deepens, the distal end becomes dark, 

 and gelatinization proceeds from this point upward. Only occasionally does gelatinization begin 

 at both ends. In the T-shaped, boot-shaped, and related forms the distal end of both primary and 

 secondary sets of lamellae darken and gelatinize. Occasionally the distal end of the secondary set 

 alone, or with the proximal and the distal ends of the primary set, will darken and gelatinization 

 will proceed from these points. There may be small protuberances from irregular points on the 

 grain if the grain is slow in reacting. Most of the swollen grains present the alternate light and dark 

 banded appearance noted in the other starches of the genus and retain much of the original shape 

 of the grain. The hilum is marked by a clear, round spot surrounded by a narrow, clear, light ring. 

 The round ovoid and related forms have not the striated appearance observed in other forms. When 

 the reaction is complete the central parts of these grains are dark and traversed by fissures in one 

 or two directions, while at the proximal end there is usually a round light space representing an area 

 corresponding to the position of the hilum. 



The reaction with chromic acid begins in IK minutes and is complete in 5% minutes. The hilum 

 and lamellte become distinct. Longitudinal fissures extend in from the margin opposite the hilum 

 and partly divide the main bodj' of the grains. In the elliptical forms this part may be subdivided 

 regularly by transverse fissures and thus the grain mass is arranged in rows of granules similar 

 to the arrangement of the lamellse. In the irregular forms the granules seem to have no fixed 

 arrangement. The marginal parts are very distinctly marked with three or four finely striated 

 bands. When the grains are compound the two portions are separated by the banded margin of 

 the primary grain. The hilum swells together with other parts; the lower part of the grain is dis- 

 solved; then the inner granular portion; and finally, the marginal part near the hilum. Occa- 

 sionally both ends dissolve, leaving the central portion, which passes into solution later; rarely the 

 proximal end dissolves first. 



With pyrogallic add some grains are gelatinized in 1% minutes and all in 7 minutes. The hilum 

 and lamella; become very distinct; the distal end swells slightly; and longitudinal fissures extend 



Curve of Reaction-Intensities of Starch of Dieffenbachia 

 seguine var. maculata (pith). 



