462 



STARCHES OF AROIDE^. 



Reaction begins with ferric chloride in IJ^ minutes and the grains are all gelatinized in 30 min- 

 utes. The hilum becomes distinct as a dark spot or bubble. The lamellae become intlistinct. 

 Gelatinization begins usually at the distal end; the marginal part becomes clearer and the inner 

 portion opaque. The hilum often swells before other parts of the grain. The inner portion becomes 

 faintly granular and separated by transverse fissures, corresponding to some of the lamellae. Near 

 the gelatinizetl parts faint longitudinal fissures appear. The marginal part becomes homogeneous, 

 occasionally faintly striated. The grain swells slowly, becoming gelatinized from both ends, gelat- 

 inization beginning at the proximal end usually later than at distal end. The gelatinized grains 

 thus formed are very large and somewhat folded and lobulated. 



With Purdy's solution reaction begins faintly in 2 minutes in a few grains and after an hour 

 half of the grains are partially gelatinized. Both liilum and lamellte are rendered very distinct. 

 Fissures extend inward from the margin at the distal end, at which point the grain swells into a 

 gelatinous mass. Transverse fissures appear, which, together with the longitudinal fissures, divide 

 the inner portion into rows of granules. Then the hilum may swell, followed by swelling of the distal 

 end; or both hilum and distal end may begin to swell at the same time. The granular inner por- 

 tion completely gelatinizes first, then the faintly striated marginal portion. The gelatinized grains 

 are large, lobulated, and somewhat distorted. 



STARCH OF PITH OF DIEFFENBACHIA SEGUINE VAR. IRRORATA. 

 (Plate 18, figs. 105 and 106. Chart 88.) 



Histological Characteristics. In form the grains are both simple and compound, and isolated. 

 The conspicuous forms are long ellipses, usually with both ends rounded, but sometimes the distal 

 end flattened. In addition there are also narrow elliptical or fusiform grains with pointed ends, 

 the latter being due to erosion. Occasionally an elliptical grain may be more or less hooked at one 

 end. There are a few round, ovoid, oval, T-shaped, boot-shaped, boomerang-shaped, and related 

 forms whose peculiarities of shape are due to secondary deposits of lamelke. The lower proportion 

 of grains having secondary deposits is very striking, and in this respect the grains are more like 

 those of D. scguine var. nobilis than those of D. seguine var. maculata and D. illustris. 



The hilum is a small, refractive spot, fairly distinct, and not fissured in any grain. It is eccentric 

 in the elongated forms about two-fifths the longitudinal axis, and is generally in the median line. 

 In grains having one end smaller than the other, the hilian 

 is usually at the smaller end, contrary to what is com- 

 monly observed in D. seguine var. maculata and D. seg- 

 uine var. nobilis. 



The lamellcB are distinct, regular or irregular circles 

 or ellipses, or segments of circles or ellipses, often flattened 

 and wavy. Only those about the hilum are circular and 

 most of them are segments of curves. The lamellae vary 

 in size and sjjacing in the same grain and in different 

 grains. In the boot shape and T shape and related 

 shapes, there are two or three distinct sets of lamelke, 

 which may be more or less distorted. The number of 

 lamellae varies from 15 on the small to 48 on the large 

 grains. The average is about 30. 



The grains vary in size from 5 to 40//. The common 

 size is 27/1. The grains are commonly one-fourth to one- 

 half as broad as they are long and about two-thirds as 

 thick as broad. 



Polariscopic Properties. The figure in the elongated 

 grains is very eccentric; it is distinct and fairly clear-cut. 



The lines are generally narrow and not clear-cut, often bent somewhat or otherwise distorted. As 

 the grains are transitional between the elongated and round forms, the figure becomes less eccentric, 

 so that in the few round forms it may be in the shape of a cross. 



The degree of polarization is fairly high, but lower than D. seguine var. nobilis, varying in differ- 

 ent grains and in different aspects of the same grain, highest when the grain is viewed from the end 

 or edge. 



Curve of Reaction-Intensities of Starch of Dieffenbachia 

 seguine var. irrorata (pith). 



