448 



STARCHES OF AROIDE^. 



The hilum is a very distinct, light, round spot, generally in the median line and somewhat eccen- 

 tric, usually deeply fissured. In many instances the fissures extend throughout the greater part of 

 the grain. The 3-armed fissure is the most common. The main fissures frequently are subdivided. 

 Occasionally there is a fissure consisting of a single line which is transverse or longitudinal. 



The lamelUe are fairly distinct, rather fine, regular, concentric rings, some much coarser and 

 more distinct than others; commonly one is especially distinct near the hilum. They are circular 

 near the hilum, but those near the margin tend to follow 

 its outline. They vary in number from 8 to 15. 



The grains vary in size from 4 to 3(5/i- The common 

 size is 22ju. 



Polariscopic Properties. The figure is very distinct 

 and generally slightly eccentric. The lines are broad and 

 ragged and of about the same distinctness throughout 

 their length, commonly tending to broaden as they ap- 

 proach the margin. 



The degree of polarization is fairly high, higher when 

 the grain is viewed from an end, and higher than in Arum 

 cornulum. 



With selenite the quadrants are fairly well defined, 

 usually regular in shape, but unequal in size. The colors 

 are as a rule pure. 



Iodine Reactions. With 0.25 per cent Lugol's solu- 

 tion the grains color at once quite deeply a blue-violet; 

 with 0.125 per cent solution they tint readily, the color 

 deepening cjuickly. After heating in water until the 

 grains are completely gelatinized, the solution is some- 

 what colored on the addition of iodine, while the gelatinized grains usually become deeply colored, 

 some lightly. After boiling 2 minutes the solution is colored blue deeply, and the grain-residues a 

 violet with an excess of iodine. 



Staining Reactions. With gentian violet the grains begin to stain in 2 minutes and at the end 

 of 30 minutes are fairly deeply to deeply colored. This reaction is of the same intensity as that 

 of Arum cornutum. 



With safranin the grains stain very slightly in 2 minutes and after 30 minutes they are very 

 slightly stained, but not so deeply as Arum cornutum. 



Temperature Reaction. The temperature of gelatinization is 63.5 to 65 C, mean 64.25. 



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

 almost all the grains are darkened in 10 minutes. A few grains are affected only at the corners 

 of the facets. The hilum is distinct, especially if it be fissured. The lamellae are somewhat obscured, 

 not particularly so. The margin becomes slightly clearer, then darkens, generally first around the 

 facets and then around other parts. The dark color spreads inward, often appearing to advance 

 more along certain radial lines than others, until the whole grain is darkened, accompanied by a 

 very shght swelling, especially of the corners of the facets, with no irregular protrusions. The 

 gelatinized grains so formed are not very large and are of uniform color, except that some show 

 a large, light, inner space representing the swollen hilum. Large light fissures often occupy the 

 position of the fissures in the normal grain. 



Reaction with chromic acid begins in 30 seconds and is over in 7 minutes. The hilum and 

 lamellae become distinct. The grain becomes traversed throughout by very fine striae radiating from 

 the hilum, which become more and more distinct as the hilum swells. Any fissures present at the 

 hilum disappear. The inner portion of the grain is transformed into a gelatinous mass, and the 

 more resistant outer starch forms a thick marginal ring with fine striations and alternate refractive 

 and non-refractive bands. The grain becomes spherical and the marginal band gradually grows 

 thinner, clearer, and quite homogeneous. This band or capsule now invaginates in several places, 

 one part is dissolved and the granular contents are poured out and dissolved, followed by solution 

 of the rest of the capsule. 



With pyrogallic acid reaction begins in VA minutes and is over in 13 minutes. The hilum and 

 lamellae are distinct. Fine striie radiate from the hilum as this part swells; as they grow more 



