466 



STARCHES OF AROIDEiE. 



Chart No. 90. 



P I GV T 

 S 



CI CA PA FC 



PS CI PA 

 ~ POPS 



The reaction with Purdy's soItUion begins in 2 minutes. At the end of 15 minutes all the grains 

 are affected, but after 45 minutes only one-fifth are completely gelatinized, and at the end of an 

 hour the reaction has not progressed further. The hilum and lamella; are very distinct. The inner 

 part of the grain becomes fissured by longitudinal fissures extending in from the distal end and by 

 transverse fissures having the direction of the i)rincipal lamellse, forming rows of granules. The 

 outline of the grain appears wavy and irregular. The hilum swells slightly and refractive lines 

 appear in each side, dividing the inner part from the margin, but these lines are not so prominent 

 as with other reagents. Swelling proceeds inward from the distal end, the grain swells laterally 

 and then l)ecomes gelatinous, the granules disappearing and the margin clearing later. The gelatin- 

 iited grains are large, crumpled, and lobulated. 



STARCH OF PITH OF DIEFFENBACHIA ILLUSTRIS. (Plate 19, figs. 109 and 110. Chart 90.) 



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

 always isolated. They are very irregular in shape, the fundamental type elliptical, with a marked 

 tendency for lateral curvature, the degree of bending ranging from a slight curvature to 45° or 

 more, thus giving rise to forms varying from elliptical to the boomerang-shaped. The proximal end 

 may be the narrower or the broader, and the distal end is often flattened. There are some T-shaped, 

 ovoid, oval, round, and various irregular forms. On the whole there is a greater variety of shapes 

 than in other Dieffenbachia starches. The T-shaped, 

 boot-shaped, boomerang-shaped, ovoid, and irregular 

 grains are flattened, but the elliptical forms are round 

 or nearly so, also often showing irregularities from every 

 aspect; from the end they appear round, oval, or some- 

 what irregular. 



The hilum is a fairly distinct, small, non-refractive 

 spot, occasionally showing a slight transverse fissure, usu- 

 ally eccentric about one-third to two-fifths of the longi- 

 tudinal axis and placed to one side of the median line. 

 Multiple hila were not noted. 



The lamelbe are distinct rings, ellipses, or segments 

 of rings or ellipses, which are probably continuous; in the 

 elliptical grains they are usually flattened at the distal 

 end, sometimes wavy. In boot and T shapes and in the 

 irregular forms there are two or more sets of lamellae, sec- 

 ondary sets being superposed on the primary. The lamel- 

 lae vary in distinctness, size, and spacing in the same grain, 

 those making up the secondary and tertiary sets being 

 wider and further apart. The sets differ also in distinct- 

 ness, varying in number from 15 on the smaller grains to 48 on the larger, the average being about 30. 



The grains vary in size from 7 to 60;^, the common size being about 35/^. They are commonly 

 one-fourth to one-half as broad as long. 



Polariscopic Properties. — The figure is very eccentric in the elongated grains and in the round 

 forms slightly eccentric. The lines are distinct with ragged edges. In grains with secondary lamellse 

 the figure is very variable in form. 



The degree of polarization is high, higher than in D. seguine var. nobilis, not so high as in D. 

 seguine var. maailata; it varies in different grains and according to the position of the grain, and 

 is highest when the grain is seen from the end. 



With seleniie the quadrants are well defined, but very irregular in shape and size. The colors 

 are fairly pure, but better than in D. seguine var. nobilis. 



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

 with 0.125 per cent solution they color lightly. The depth of color is in both reactions greater than 

 in grains of D. seguine var. nobilis. After heating until all the grains are gelatinized the solution 

 and the grains are very deeply colored with iodine. The gelatinized grains are somewhat crumpled, 

 but many retain some of the original form. After boiling 2 minutes, the solution was colored very 

 deeply and the grain-residues less deeply with iodine. With excess of iodine, the capsules are colored 

 red and much crumpled, some being reduced to granular masses. 



Curve of Reaction-Intensities of Starch of 

 Dieffenbachia illustris (pith). 



