GENUS DIOON. 



897 



The degree of polarization is high. There is a variation among the grains, some being much 

 higher than others. 



With selenite the quadrants are well defined, but generally unequal in size and uregular in 

 shape. The colors are usually pure. 



Iodi7ie Reacliom. With 0.25 per cent Lugol's solution the grains color a fau-ly deep reddish- 

 violet, which deepens rather slowly; with 0.125 per cent solution the grains color a light reddish- 

 violet, which tlei'iiens rather slowly. After heating in water until all the grains are completely gelat- 

 inized and then adding iodine, the solution is colored a deep indigo-blue, the gi-ains a deep blue 

 with a reddish tint, and the capsules a reddish-violet to an old-rose. After boiling for 2 minutes 

 the solution becomes more deeply colored, but the grain-residues of a much lighter color, on the 

 addition of iodine. With an excess of iodine the grain- 

 residues become a deeper blue and the capsules a deep 

 old-rose to a wine-red. 



Staining Reactions. With gentian violet the grains 

 begin to color immediately. In 30 minutes the smaller 

 grains, which are much more numerous, stain lightly, 

 while the larger ones are fairly colored. 



With safra7ii7i the grains begin to color immediately. 

 In 30 minutes the smaller ones are fairly colored and the 

 larger ones rather deeplj'. 



Temperature Reaction. The temperature of gelatin- 

 izatiou is 72 to 73 C, mean 72.5. 



Effects of Various Reagents. With chloral hydrate- 

 iodine the reaction begins immediately. Some grains are 

 gelatinized in a minute, nearly all in 13-2 minutes, and all 

 but rare resistant grains in 2 minutes. The reaction is 

 complete in all in 4 minutes. The grains are colored a 

 deep old-rose immediately and the hilum and fissures be- 

 come very dark. Gelatinization begins at the distal end, 

 accompanied by a deep bluish color which gradually spreads around the margin and then advances 

 rapidly towards the hilum from the distal end until the entire grain is gelatinized and deeply colored. 

 The gelatinized grains are swollen, but retain the shape of the untreated grain. 



The reaction with chromic acid begins immediatelj'. A few grains are dissolved in 30 seconds, 

 nearly all in a minute, and all but parts of a few resistant grains in 2 minutes; the reaction is complete 

 in these latter usually in 2] o noinutes, rarely 3J^^ minutes. The hilum swells rapidly, and as the 

 surrounding starch is gelatinized a mass of refractive granules appears and the outer lamellae be- 

 come very distinct and striated. The capsule ruptures at the distal end and solution of the exuding 

 contents and capsule rapidly follows, a small area of outer lamellae at the proximal end being the 

 last to disappear. 



Reaction with pyrogallic add begins at once. A few grains are gelatinized in 15 seconds and 

 all in 30 seconds. The hilum swells, and two longitudinal fissures, one on each side of the hilum, 

 extend towards the distal margin. The part of the grain between these fissures is quickly gelat- 

 inized and the distal end swells and becomes distorted. The outer lamellae at the sides and proxi- 

 mal end gTOW distinct and striated, and are more resistant, but soon gelatinize. The reaction is 

 so rapid that the details can not be accurately determined. The gelatinized grains are much swollen 

 and distorted. 



The reaction with ferric chloride begins in a few grains in 30 seconds. A small number are gelat- 

 inized in 1^2 niinutes, more than half in 3 minutes, nearly all in 5 minutes, and all but rare resistant 

 grains in 8 minutes. The reaction is usually complete in the latter in 10 minutes, rarely not until 

 20 minutes. The hilum and fissures become very distinct. A border which is lustrous and appears 

 transparent forms marginally. Gelatinization usually begins at the distal end, accompanied by 

 rapid distension of the capsule, and advances gradually towards the proximal end, at which point 

 the resistant starch is broken into several large, refractive granules that are finally gelatinized. 

 The gelatinized grains are much swollen and distorted. 



The reaction with Purdy's solution begins in a few grains in 30 seconds. A small number are 

 gelatinized in 5 minutes; about one-tenth are completely gelatinized and about half are partially 



Curve of Reaction-Intensities of Starch of Dioon edule. 



