GENUS DIEFFENBACHIA. 



461 



acteristics as in the pith starch. Owing to the peculiar optical effects produced by additions to the 

 primary grain, as in the T and boot forms, the figure may be much modified. In the round and 

 ovoid forms the figure is in the form of or an approach to a cross, as in the pith starch. 



The degree of polarization is high, lower than in the pith starch, highest when the grain is viewed 

 from the end or edge. 



With selenite the quadrants are sharply defined, but vary in shape and size, as in other Dieffen^ 

 bachia starches. The colors are pure. 



Iodine Reactions. — With 0.25 per cent Lugol's solution the grains color a deep blue-violet; 

 with 0.125 per cent solution they color quite readily. No differences could be noted between pith 

 and cortex starches in this reaction. After heating until all the grains are completely gelatinized, 

 the solution is colored indigo, while the grains stain deeply. The grains are large and somewhat 

 crumpled, but retain some of the original form. After boiling for 2 minutes the solution is colored 

 deeply and the grain-residues very lightly. With an excess 

 of iodine the capsules become reddish or reddish-violet. 

 They are not so readily reduced to granular masses as 

 the grains of D. seguine var. irrorata or D. illustris. 



Staining Reactions. — With gentian violet the grains 

 begin to stain in 2 minutes, but after 30 minutes are only 

 deeply stained. The pith and cortex starches are colored 

 about equally. 



With safranin the grains begin to stain in a minute, 

 some more deeply than others, and after 30 minutes are 

 fairly deeply stained. The cortex starch stains less deeply 

 than that of the pith. 



Temperature Reaction. — The temperature of gelati- 

 nization is 70° to 71.2° C, mean 70.6°. 



Effects of Various Reagents. — With chloral hydrate^ 

 iodine the reaction begins in Ij^ minutes in all the grains 

 and with three-fourths is over in an hour. The hilum be- 

 comes distinct as a dark spot or bubble. The lamellae are 

 not rendered more distinct. The margin opposite the 

 hilum darkens and protrusion begins. If there are two 

 sets of lamellae, the distal end of each set may darken, or the hilum and the distal end may at the 

 same time darken. Darkening and gelatinization spread over the whole grain from these points. 

 The gelatinized grains thus formed are marked by transverse lines, giving the grain a resemblance 

 to annelid worms, as before noted. The grains are not much distorted and are enlarged principally 

 longitudinally. Some forms show a dark fissured mass in the central portion near and sometimes 

 obscuring the swollen hilum. 



The reaction with chromic add begins in 30 to 60 seconds and all of the grains are dissolved 

 in 5 minutes. Both hilum and lamellte are rendered more distinct. The hilum swells somewhat 

 and a refractive line appears on each side, sharply defining the inner area of the grain. The latter 

 becomes divided into rows of granules by longitudinal fissures projected from the distal end in con- 

 junction with transverse fissures which appear in the lines corresponding to the most prominent 

 lamellae. The margin becomes very well defined and very wide, and shows several distinct, finely 

 striated bands. The hilum swells, the refractive lines at the side widen, and the grain begins to 

 dissolve, usually from the distal end, which widens out. The granules disappear from the distal 

 end up, followed by solution of the marginal part. Occasionally both ends dissolve, leaving the 

 central portion, which disappears slowly. 



Reaction begins with pyrogallic acid in 30 seconds and all the grains are gelatinized in 7 minutes. 

 Both hilum and lamelUe become distinct, and longitudinal fissures extending from the distal end, 

 together with transverse fissures, divide the inner part of the grain into a granular mass. The marginal 

 part becomes denser and shows fine striations and obscure bands. Gelatinization begins at the distal 

 end, and the grain becomes traversed by transverse fissures which give it the annelid appearance 

 described under the chloral hydrate-iodine reaction. The hilum and the granules swell, the granular 

 appearance vanishes, and the margin clears later. The gelatinized grains are very large and many 

 are much crumpled and lobulated. Some approach a more or less oval form and are smooth. 



Curye of Reaction-Intensities of Starch of Dieffenbachia 

 seguine var. maculata (cortex). 



