GENUS ARUM. 441 



crumpled. After boiling the preparation for 2 minutes, the solution is colored deeply, but the 

 grain-residues lightly or not at all upon the addition of iotline. On the addition of a slight excess 

 of Lugol's solution the capsules color a violet. 



Slaining Reactions. With genlinn violet the staining begins in .5 minutes and in 30 minutes 

 it is light. 



With safranin the staining begins in 1}/^ minutes, but at the end of 30 minutes the grains are 

 only lightly colored. With this stain the color of the grains is not as deep as that of A. cornutum, 

 but deeper than that of A. italicum. 



Temperature Reaction. The temperature of gelatinization is 70 to 71 C, mean 70.5. 



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

 all the grains are darkened and the reaction over in 8 minutes. The hilum becomes prominent, 

 but the lamelljp, except those especially distinct, are obscured. The grains are colored violet and 

 begin to darken, especially at the edges and corners of the facets. The whole margin becomes dark, 

 and this color spreads inward until the entire grain is colored. The grains swell somewhat during 

 this process and become gelatinous. The gelatinized grains formed are not very large; they are 

 rounded, and retain much of the original form. The color is uniformly a dark indigo, except for 

 a clear, light, round space at or near the swollen hilum. 



The reaction with chromic acid begins in 30 seconds and is over in 10 minutes. The hilum is 

 very distinct, but the lamellae not especially so. The hilum swells slightly, and fine stria; radiating 

 from the hilum appear on all throughout the grain. These striae become larger and more distinct, 

 often in a stellate form, as the hilum continues to swell. The undissolved part of the grain is pushed 

 out to the mai'gin, and there is formed a marginal band consisting of two layers, the inner being a 

 single layer of large, distinct, mdely separated granules, and the outer a comparatively thin, finely 

 striated band, which does not show the alternate refractive and non-refractive lines so plainly as in 

 some of the starches of other genera; this band becomes thinner and clearer as the grain continues to 

 swell, often growing much distorted by invaginations. P'inally, the capsule dissolves at one point, 

 allowing the inner granular matter to flow out and dissolve, followed by the solution of the cajisule. 



Reaction with pyrogallic acid begins slightly in 2 minutes and is over in 15 minutes. The hilum 

 becomes prominent, liut the lamella^ are not rendered more distinct. The hilum swells slightly 

 and fine striae appear, radiating from the hilum and becoming larger and more distinct. The non- 

 refractive lines radiating from the hilum to the corners of the facets now become very clear. The 

 hilum continues to swell slowly, the mass of the grain swelling at the same time. The more resistant 

 starch at the margin forms a band of two layers, one being in the form of a single row of granules, 

 the other a rather thin, homogeneous band which shows fine strife and indistinct, alternate refrac- 

 tive and non-refractive lines. The gelatinized grains are fairlj' large, not much distorted, folded, 

 or crumpled, and retain much of the original shape of the grain. 



With ferric chloride reaction begins in 2 minutes and is over in 30 minutes. The hilum is quite 

 distinct, but tlie lamellae are invisible. The margin becomes clear and darker, but the inner por- 

 tion of the grain appears lighter and opaque. The hilum begins to swell and two lines appear, 

 which run to the corners of the facets. The hilum swells slowly and fine striae arise throughout 

 the substance of the grain. A band formed at the margin consists of an inner single row of coarse 

 granules and an outer striated part formed of ungelatinized starch. This band becomes thinner, 

 clearer, and quite homogeneous. Or the grain may gelatinize quicklj^ and the hilum may swell 

 without becoming very prominent. The gelatinized grains are not much distorted. When the 

 process is slower, there is some sign of preliminary gelatinization of the margin, but this mode of 

 dissolution is rare. 



With Purdy's solution the reaction begins very slightly in 10 minutes. After 2 hours onl}^ about 

 half the grains are at all affected anfl very few are completely gelatinized. The hilum and lamellae 

 become very distinct. Often the only change noted was the swelling of the hilum and the appearance 

 of fine striae throughout. As this process progresses, the inner portion of the grain is gelatinized, and 

 the more resistant marginal portion forms a thick band, but the reaction does not go any further. 



ST.\RCH OF ARUM CORNUTUM. (Plate 14, figs. 79 and 80. Chart 77.) 



Histological Characteristics. In form the grains are simple and for the most part isolated; 

 nearly all show one or more facets. Small aggregates of two or three or more grains are seen, and 

 also rare larger aggregates. The pressure facets are not usually so sharply defined as in other Arum 



