770 



DATA OF PROPERTIES OP STARCHES OF PARENT- AND HYBRID-STOCKS. 



The lamella are not generally demonstrable. The 

 surface of the grain, with the exception of a few large 

 scattered grains, is either homogeneously refractive, or 

 the main body is hetcrogeneously refractive, and is 

 usually completely surrounded or bounded at the proxi- 

 mal end and sides by a narrow more refractive border 

 in which usually but 1, rarely 2 or 3, lamellae are demon- 

 strable. The heterogeneous type with refractive border 

 is much more frequent than the homogeneous type. 



The size varies from the smaller which are 6 by 5/i, 

 to the larger which are 38 by 36/*; commonly about 24 

 to 22/i in length and breadth. The size of the scattered 

 large grains is not given as it would be misleading in 

 comparative study with other species. 



POLARISCOPIC PBOPERTIES. 



The figure varies from centric to quite eccentric. The 

 figure is not clean-cut in most of the grains, the lines 

 not being distinct. In such grains a narrow band at 

 the margin is arranged either in the form of a square 

 or rectangular box which is always pierced at the corners, 

 and sometimes as well at 1 or more points on the sides. 

 In the few scattered grains in which the figure is distinct, 

 the lines vary from moderately fine to coarse and either 

 intersect at right angles, obliquely, or are so arranged 

 as to form a mesial line with bisected ends. The lines are 

 more frequently straight but may be either bent or 

 bisected. Occasional double or multiple figures are 

 observed. 



The degree of polarization varies from low to very 

 high (value 55). In most grains there is a great varia- 

 tion in the same aspect of a given grain since it is either 

 very low or lacking in the mesial portion and usually 

 high in a narrow band at the margin. A few scattered 

 grains occur in which the polarization is high to very high 

 throughout the quadrants. 



With selenite the quadrants in most of the grains are 

 not well defined with the exception of a narrow border 

 at the margin, while in a few scattered grains they are 

 very sharply defined. They are usually unequal in size, 

 and sometimes irregular in shape. The colors are usually 

 impure ; the impurity generally indicated by a purplish 

 and orange color, although a greenish tinge appears in 

 some of the scattered grains with sharply defined quad- 

 rants. The colors in these scattered grains are more 

 frequently pure. 



Iodine Reactions. 



With 0.25 per cent Lugol's solution the grains imme- 

 diately color a light to moderate (value 40) reddish violet, 

 which quickly becomes moderate to moderately deep with 

 slightly bluer tint, the scattered large grains usually be- 

 ing deeper and bluer in tint than the typical smaller 

 grains. With 0.125 per cent Lugol's solution most of the 

 grains color very_ light to light with rare moderate reddish 

 violet, most of them become moderate and still remain 

 reddish in tint, but a few become moderately deep and 

 bluish, among which are the scattered large grains, al- 

 though some of these also remain moderate and reddish 

 in tint. After heating in water until all the grains are 

 gelatinized and then adding 2 per cent Lugol's solution 

 most of the gelatinized grains become dark, and a few 

 light blue, all with reddish tint, so that most of them 

 appear a deep purple. Some of the scattered large grains 

 are of a very deep purplish-blue. The solution is bluish 

 green. If the preparation is boiled for 2 minutes, and 



then treated with an excess of 2 per cent Lugol's solution, 

 the typical grain-residues become a light blue, and the 

 scattered large ones a deep blue, all with reddish tint ; the 

 capsules color a wine-red to a deep brownish-red, and 

 the solution is a deep bluish-green. 



Aniline Reactions. 



With gentian violet the grains stain immediately 

 very lightly to moderate, more of the former, and in half 

 an hour they become moderate to moderately deep, with 

 a slight predominance of former (value 55) . The typical 

 grains are usually lighter at the entire margin of rounded 

 grains and at the distal margin of the slender forms. 

 A few large scattered grains occur in which 1 lamella 

 stains more deeply, cutting off a distal marginal border 

 from the main body ; this border occasionally also appears 

 deeper in color. 



With safranin the grains immediately become light 

 to moderate, fewer of the latter, and in half an hour they 

 are moderate to moderately deep, with a majority of the 

 latter (value 60). The grains stain a little more deeply 

 with safranin than with gentian violet. A variation in 

 the depth of the areas of the different types of grains is 

 the same as with gentian violet. 



Temperature Reactions. 

 The majority of the grains are gelatinized at 74° 

 to 76° C, and all are gelatinized at 75° to 77° C, 

 mean 76° C. 



Effects of Various Reagents. 



The reaction with chloral hydrate begins immediately. 

 Complete gelatinization occurs in about 45 per cent of the 

 entire number of grains and 65 per cent of the total 

 starch in 5 minutes; in about 60 per cent of the grains 

 and 75 per cent of the total starch in 15 minutes; in 

 about 76 per cent of the grains and 88 per cent of the 

 total starch in 30 minutes; in about 78 per cent of the 

 grains and 90 per cent of the total starch in 45 minutes ; 

 in about 80 per cent of the grains and 92 per cent of the 

 total starch in 60 minutes. (Chart D 619.) 



The hilum is usually not visible, but occasionally 

 appears as a large refractive spot, in which a bubble 

 sometimes forms. The lamella? are not visible. A nar- 

 row refractive band is slowly formed about the margin 

 of the grain and recedes before the advance of gelatiniza- 

 tion from the margin. The material of the grain usually 

 assumes a pitted appearance before gelatinization begins, 

 and gelatinization may begin either in the interior of the 

 grain or at prominent points of the distal margin. In 

 the first-named grains gelatinization of the whole grain 

 proceeds with great rapidity, and much swelling; in the 

 second-named grains the distal marginal starch gelati- 

 nizes and gelatinization proceeds toward the proximal 

 end. The ungelatinized material separates in successive 

 layers, suggesting a lamellar structure, which is not other- 

 wise demonstrable. Gelatinization as a rule proceeds 

 more rapidly along the margin than in the interior of the 

 grain, and therefore the gelatinized marginal starch may 

 completely surround the more resistant inner starch. 

 The most resistant starch is usually found just distal 

 to the hilum if the hilum is visible, otherwise in the 

 central portion of the grain. The gelatinized grains are 

 large and much distorted, and do not retain much of 

 the original form of the grain. 



