460 STARCHES OF AROIDE^. 



inward and transverse fissures appear, causing the inner portion to become granular. The granules 

 are arranged in regular lines, corresponding with those of the lamellae. The marginal parts become 

 more distinct, finely striated, and indistinctly banded. The hilum swells greatly and the granules 

 generally disappear, sometimes leaving a finely granular mass at the distal end of the grain. Later, 

 the margin clears, or the distal end may swell, the granules at this part disappearing and the swell- 

 ing extending upward. The hilum is the last part to swell, followed by clearing of the margin around 

 the hilum. The gelatinized grains are very large, somewhat crumpled, and lobulated. The proxi- 

 mal end is smooth and rounded and the distal end crumpled and lobulated. 



Reaction with ferric chloride begins in 2 to 5 minutes and is over in 25 minutes. The hilum 

 becomes distinct as a dark spot or bubble, and the lamellae disappear. The periphery of the grain 

 becomes clear and darker, causing the inner part to appear light and opaque. In this lighter por- 

 tion the lines of the lamellae reappear. The distal end now becomes gelatinous and longitudinal 

 striae extend inward. In swelling, the gelatinized starch spreads out widely on all sides. If there 

 are two sets of lamellae this process usually begins at the distal end of the secondary set. Gelatiniza- 

 tion proceeds and the inner portion becomes granular just above the swelling portion as the process 

 advances up the grain. The hilum is finally included and in expanding extrudes the proximal margin, 

 which is finely striated and shows indistinct bands. Occasionally the hilum swells first and the 

 other part of the grain becomes gelatinized afterwards, the inner portion being coarsely granular 

 and the periphery finely striated. The gelatinized grains are very large, commonly ovoid in form, 

 and much folded and lobulated at the distal end. They retain little of the original form of the grain. 



Reaction with Purdy's solution begins in some grains in 2 minutes and about half of the grains 

 are only partially gelatinized in iK hours. Both hilum and lamellae become very distinct. The inner 

 part of the grain is divided by longitudinal and transverse fissures. The margin is distinct and 

 striated. Swelling may begin at either end, or in the central portion of the grains, causing the 

 formation ultimately of an oval mass. The granules formed attending the fissuration above referred 

 to gradually disappear as the grain swells, followed by a clearing of the margin. The gelatinized 

 grains are very large and somewhat folded, and retain but little of the original form. 



STARCH OF CORTEX OF DIEFFENBACHIA SEGUINE VAR. MACULATA. 

 (Plate 18, figs. 103 and 104. Chart 87.) 



Histological Characteristics. — In form the grains are both simple and compound, and are iso- 

 lated. Like the pith starch the grains are irregular in shape and exhibit many forms, the multi- 

 pUcity of which is due to lamellar deposits upon the original or primary grain. The conspicuous 

 forms are round, ovoid, oval, elliptical, T-shaped, boot-shaped, boomerang-shaped, and transitional. 

 Seen from the edge, the grains of the round and elliptical types appear of the same thickness as 

 width, but those of irregular form and the T and boot shapes, etc., are somewhat flattened. From 

 the end the grains appear round or oval. In preparing the cortex starch much of the pith was 

 included, so that there is a considerable admixture of the latter starch. The pure cortex starch, 

 Hke that of D. seguine var. rwbilis, shows a marked tendency to the elliptical form and a consequently 

 lessened tendency for the appearance of the round and freak types so conspicuous in the starch 

 of the pith. 



The hilum is a distinct, relatively large, round, non-refractive spot, less often fissured than even 

 the pith starch. It is usually eccentric about two-fifths to one-fifth of the longitudinal axis of the 

 elongated grains and commonly in the median line, generally at the larger end in grains of ovoid 

 and related forms. It is never double. 



The lamellai are very distinct regular and irregular rings or ellipses or segments of circles or 

 ellipses, commonly following the outlines of the margin, except those near the hilum, and occasionally 

 wavy. The boot and T shapes and related forms have two or three sets, the additional sets being 

 added to the primary set. The lamellae vary in distinctness, size, and spacing in the same grain 

 and in different grains, and where there are two or three sets those of the additional sets are usually 

 larger, coarser, and more distinct. If the grains have one set of lamellae, those near the margin are 

 usually the more distinct. The number ranges from 15 on the small to 48 on the large grains, the 

 average being about 30. 



The size varies from 7 to 52/<. The common size is 27ti. 



Polariscopic Properties. — The figure in the elongated forms is very eccentric and generally 

 distinct and clear-cut. The lines are broad, ragged, and irregular, with the same general char- 



