716 STARCHES OF IRIDACE.E. 



deeply and the grain-residues fairly. On the addition of an excess of iodine the capsules color a 

 red-violet, and most of them are seen to retain some blue-reacting starch. 



Staining Reactions. With gentian violet the grains begin to stain very faintly in 2 minutes 

 and in 30 minutes they are very lightly stained. 



With safranin the grains begin to stain very lightly at once and in 30 minutes they are fairly 

 stained. 



Temperature Reaction. The temperature of gelatinization is 78 to 79 C, mean 78.5 



Effects of Various Reagents. With chloral hydrate-iodine reaction begins in most grains in 2 

 minutes; about one-fifth are gelatinized in 20 minutes, one-half in 35 minutes, and three-fourths in 

 1}4 hours. The reaction begins at the corners and edges of the facets at the distal end, which darken 

 and swell slowly and shghtly ; this process usually extends about the entire margin of the grain and 

 then inward over the whole interior of the grain. The line of demarcation between the gelatinized 

 and the ungelatinized portions is never very marked. The gelatinized grains are not large, are of 

 uniform dark color, and retain much of the original form of the grain. 



The reaction with chromic acid begins in a minute and is over in 7 minutes. The hilum swells 

 and from it fine striae radiate in all directions. The inner portion of the grain is converted into a 

 gelatinous mass, the whole grain swells, and the fine striae become coarse and very distinct. The 

 resistant marginal starch forms a band or ring of granules which surrounds the inner, gelatinous 

 mass, becomes thinner and transparent, and is fuially dissolved at one point, usually the corners of 

 one of the facets; gelatinized starch flows out and is dissolved and the remainder of the band slowly 

 passes into solution. 



Reaction with pyrogallic acid begins in many grains in a minute; all are partially gelatinized 

 in 8 minutes, two-thirds completely in 18 minutes, and nearly all in 30 minutes. The reaction 

 begins at the hilum, which swells slightly, and fine striae radiate from this point. The inner portion 

 is then changed into a gelatinous mass and the marginal area forms a band very distinctly striated. 

 The grains swell slowly and to a great size, and the marginal band grows thinner and transparent 

 until it becomes a very thin, homogeneous envelope. The gelatinized grains are large, but not much 

 distorted, wrinkled, or folded, and retain much of the original form. 



With ferric chloride the reaction begins in a few grains in a minute. About two-thirds are 

 gelatinized in 15 minutes and all in 45 minutes. The reaction usually consists in swelling of the 

 hilum, followed by progressive gelatinization from the interior outwards. This process is accom- 

 panied by a steady, slow swelling; but in some grains the corners of the facets at the distal end become 

 gelatinous and swell before the process begins in other parts, after which the reaction is the same 

 as that described above. The gelatinized grains are large, not distorted, wrinkled, or crumpled, 

 and retain much of the original form of the grain. 



Reaction with Purdy's solution begins slightly in a very few grains in a minute. There is no 

 further change. 



STARCH OF GLADIOLUS PRIMULINUS. (Plate 69, figa. 409 and 410. Chart 273.) 



Histological Characteristics. In form the grains are simple and isolated. There are no aggre- 

 gates and few clumps. Most of the grains are marked by one or more pressure facets. The surface 

 of the grains is regular but varied in form, owing to variation in the number, form, and arrangement 

 of the facets. Small grains, chiefly round or polygonal, are very abundant. The conspicuous forms 

 are polygonal and much varied, owing to the peculiarities of the pressure facets; also spherical, 

 hemispherical, and sugar-loaf forms and their modifications. The grains are not flattened, and owing 

 to the abundance and other properties of the pressure facets appear of different shapes when ob- 

 served from different aspect. 



The hilum is a fairly distinct, comparatively large round spot, centric usually. It is never 

 fissured and no multiple hila were observed. 



The lamellce are invisible. 



The grains vary in size from 2 to 14/i. The common size is lOjtt. 



Polariscopic Properties. The figure is usually centric, distinct, and clear-cut. Sometimes one 

 or more of its lines are broader and not so clear-cut as the others. The lines are not bent or other- 

 wise distorted, but are sometimes placed at varying distances from one another. 



The degree of polarization is fair. It does not vary much in different grains of the same size, 

 nor in varying positions of the same grains. It is not so high as that of the grains of G. byzantinus. 



