898 



STARCHES OF CTCADACEiE. 



gelatinized in 30 minutes. The hilum is swollen and the lamellae become more distinct and striated, 

 but in an hour there is no further progress. In the dome-shaped grains a longitudinal fissure passes 

 from each side of the hilum to the corners of the distal margin and the grain is gelatinized l)etween 

 these fissures and at the distal end before the outer lamellse at the sides and proximal end are 

 affected. In ellipsoidal and ovoid grains the hilum swells and a single longitudinal fissure passes to 

 the distal end. Gelatinization proceeds also more rapidly in these grains at the distal than at 

 the proximal end. 



GENUS ZAMIA. 



Zamia includes about 30 species, all natives of tropical and subtropical America. Florida 

 species, Z. floridana DeCand. and Z. pumila Linn, (both frequently sold as Z. integrifolia Ait.), 

 are important sources of a form of arrowroot known as comptie or Florida arrowroot (see Maran- 

 tacece, p. 471). Starch was prepared from a specimen of Z. integrifolia obtained from the Botanical 

 Garden of the University of Pennsylvania. 



STARCH OF ZAMIA INTEGRIFOLIA. (Plate 102, figa. 609 and 610. Chart 397.) 



Histological Characteristics. — Inform the grains are simple with the exception of some compound 

 grains of few components. There are a few aggregates and clumps. Well-marked pressure facets 

 are found on some grains. The grains are often irregular as the result of depressions on the surface, 

 of variations in the length of the sides, or of protuberances, chiefly in the form of a conical pro- 

 jection at the proximal end. The conspicuous forms are 

 the almost round, ovoid, ovoid with distal end squared, 

 dome-shaped, rounded triangular, and ellipsoidal. There 

 are also hemispherical, lenticular, and various incidental 

 forms. 



The hilum may be observed as a clear, round, or 

 elliptical spot, usually eccentric, even in some of the 

 almost round grains. The eccentricity has a range of 

 about one-sixth to two-fifths of the longitudinal axis. The 

 hilum may be fissured by two diagonal clefts, which in- 

 tersect and form a cross, or by an irregular group of 

 ragged fissures. A small round or lenticular cavity may 

 be observed at the hilum. 



The lamellce are not distinct, but in some grains from 

 8 to 14 may be counted. The lamellae directly around 

 the hilum, while usually not demonstrable, may be seen 

 in the rounded grains to form complete circular rings 

 throughout the grain. The outermost lamellae in the 

 rounded triangular and the dome-shaped grains have 

 the shape of the outline of the grain. 



The grains vary in size; the smaller are 6 by 5iu; the larger are 40 by 38/u in length and breadth. 

 The common size of the nearly round forms is 16 by 15/t, of the ovoid 32 by 18^, and of the dome- 

 shaped 20 by 16ju in length and breadth. 



Polariscopic Properties. — The figure is usually from slightly eccentric to quite eccentric, but it 

 may be centric in some of the round grains of medium size. Its lines are rather broad and frequently 

 intersect obliquely; they may be straight, but frequently are bent and otherwise distorted and some- 

 times bisected. 



The degree of polarization is high to very high. The proportion of grains in which the polari- 

 zation is very high is quite large. There may also be marked variations in the same aspect of a given 

 grain. 



With selenite the quadrants are well defined, but usually unequal in size and irregular in shape. 

 The colors are generally pure, but there is a decided greenish tinge in many grains. 



Iodine Reactions. — With 0.25 per cent Lugol's solution the grains color a light red-violet, which 

 deepens somewhat slowly, some grains becoming much deeper than others; with 0.125 per cent 

 solution they tend to color very lightly, the tint deepening very slowly. After heating in water until 

 all the grains are gelatinized and then adding iodine, the solution colors a deep indigo-blue and the 



Curve of Reaction-Intensities of Starch of 2Uiinia 

 integrifolia. 



I 



