GENERA ARIS^MA AND DRACTTNCULUS. 447 



Effects of Various Reagents. — With chloral hydrate-iodine the reaction begins in a minute. About 

 half the grains are darlcened in 5 minutes and nearly all are gelatinized in 30 minutes. The hilum 

 becomes more distinct as a dark spot or fissure. The lamellae appear as they do ordinarily. The 

 whole grain is colored violet; then the faceted end begins to darken, with slight swelling. This 

 process extends over the whole grain, advancing quickly along the margin on each side, and the 

 entire grain finally becomes dark. There may be slight swelling after this. The gelatinized grains 

 are not very large, and are uniformly dark, except a central, round, clear, lighter space representing 

 the swollen hilum. 



Reaction with chromic acid begins in 30 seconds and is practically over in 5 minutes. The 

 hilum and lamella become very distinct. Fine striae radiate from the hilum and become more and 

 more distinct. The hilum swells, and subsequently the whole grain. The ungelatinized starch is 

 pushed out to the margin, where it forms a ring having two layers. The inner layer consists of coarse 

 granules, and the outer of striated refractive and non-refractive bands, which may or may not be 

 distinct. The marginal part becomes thinner and lighter as the grain continues to swell, and finally 

 invaginates at one or two places. One part of the capsule is dissolved, usually at one of the corners 

 of the facets, the granular inner contents are poured out, and with the capsule quickly dissolve. 



Reaction with pyrogallic acid begins in 30 seconds and is over in 25 minutes. The hilum and 

 lamellae become distinct. The grain is divided by fine striae which radiate from the hilum. The hilum 

 swells slowly at first, pushing out the ungelatinized starch to the margin. A very thick ring is thus 

 formed, which has the commonly observed two layers, refractive and non-refractive, both very promi- 

 nent. This ring becomes thinner and clearer, and the grain-wall or capsule frequently invaginates, 

 often at the proximal end as this end swells. Finally, a large round or ovoid gelatinous mass forms, 

 often retaining much of the original form and showing very little folding or crumpling. 



With ferric chloride reaction begins in a minute and is over in 30 minutes; a few grains are not 

 fully gelatinized even at the end of this period. The hilum is prominent as a dark spot or fissure. 

 The lamellae are not entirely obscured. The hilum swells, often fine striae radiate from it, and there 

 may be formed a characteristic banded, striated ring at the margin, though this band is not so dis- 

 tinct as it is with other reagents. If the reaction is slow there may be a preliminary gelatinization 

 of the margin. The gelatinized grains are large and not much folded or crumpled, and retain much 

 of the form of the original grain. 



The reaction with Purdy's solution begins in 30 seconds. After an hour all the grains are affected, 

 although very few are entirely gelatinized. The hilum and lamellae become very distinct. Fine 

 striae appear which radiate from the hilum and become wider and therefore more distinct as the 

 hilum swells. As the hilum swells, the inner portion of the grain is changed into a gelatinous mass. 

 The more resistant starch at the margin forms a very distinct ring of two layers, the outer being 

 distinctly striated and showing alternate refractive and non-refractive concentric bands. As the 

 reaction proceeds, this ring becomes thin and clear. The swollen grains are large and not greatly 

 folded, crumpled, or distorted. Often the reaction stops at some intermediate stage. 



GENUS DRACUNCULUS. 



The members of the genus are tuberous plants which are usually sold under the name Arum 

 dracunculus, but the genus differs from the true Arums in certain morphological characteristics. 

 Only two species are known, both native to the Mediterranean region. One of them, D. vulgaris 

 Schott, is to some extent cultivated, notwithstanding its horribly ill-smelling flowers. From this 

 species the starch was obtained. 



STARCH OF DRACUNCULUS VULGARIS. (Plate 15, figa. 85 and 86. Chart 80.) 



Histological Characteristics. — Inform the grains are simple and usually isolated; all are marked 

 with pressure facets, showing that in the plant they must have been in aggregate form. The facets 

 are generally regular in shape and with sharply defined edges. They vary in number from one to 

 four, rarely five or six. The most conspicuous forms are the ovoid, dome-shaped, hemispherical, 

 and triangular; also polygonal, spherical, and various irregular forms. It is not uncommon for 

 the dome-shaped and hemispherical forms to have three facets at base grouped about a common 

 center. Rarely, spheres are seen with one or two small, indistinct facets on the surface. The grains 

 vary in different aspects in accordance with the form, number, and arrangements of the facets; 

 on end they usually appear round. 



