516 



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



part. The number counted on some of the larger grains 

 varies from 6 to 12, usually 9. 



The size of the grains varies from the smaller which 

 are 4 by 4/i, to the larger broad forms which are 30 by 

 40/i, and the larger slender forms which are 40 by 34/i, in 

 length and breadth. The common sizes are 22 by 24/*, 

 24 by 24/* and 22 by 18/*. 



Polariscopic Properties. 



The figure is usually distinct, but in a moderate num- 

 ber of grains it is somewhat indistinct. The lines are 

 rather broad and not very clear-cut, they usually intersect 

 at an acute angle which is not very variable in different 

 grains. There are sometimes 5 lines, and the lines are 

 occasionally bisected, but they are rarely bent or other- 

 wise irregular. The figure is usually a cross but occasion- 

 ally takes the form of a conjugate hyperbole. 



The degree of polarization varies from low to very 

 high, and most of the grains have a moderate degree of 

 polarization (value 50). There is often some variation 

 in the same aspect of a given grain. 



With selenite the quadrants are usually not well de- 

 fined and commonly unequal in size and regular in shape. 

 The dolors are generally not pure, the yellow being less 

 pure than the blue. A few of the grains have a greenish 



tinge. 



Iodine Reactions. 



With 0.25 per cent Lugol's solution the grains at 

 once stain a light to moderate violet tinged with blue 

 (value 40). The color deepens with moderate rapidity 

 until it is very deep, becoming more bluish in tint. All 

 the grains are equally stained. With 0.125 per cent 

 Lugol's solution the grains color pure violet very lightly, 

 and the color deepens with moderate rapidity until they 

 are deeply colored. After heating in water until all 

 the grains are gelatinized, and then adding 2 per cent 

 Lugol's solution, the gelatinized grains all color a mod- 

 erate to moderately deep indigo; the solution is colored 

 a moderately deep indigo-blue. If the preparation is 

 boiled for 2 minutes, and then treated with an excess of 

 '.' per cent Lugol's solution, most of the grain-residues 

 color a moderate indigo-blue, and a few light indigo ; the 

 capsules color a red or a reddish violet; and the solution 

 a very deep indigo-blue. 



Aniline Reactions. 



With gentian violet the grains all color very lightly 

 at once, and in half an hour they are light to moderately 

 colored (value 30) . The grains are all stained with equal 

 intensity, and there is no variation in the same aspect 

 of the individual grains. 



With safrmin the grains all color very lightly at 

 once, and in half an hour they are moderately colored 

 (value 45). The grains are all stained with equal in- 

 tensity, and there is no variation in the same aspect of 

 the individual grains. 



Temperature Reactions. 

 The temperature of gelatinization of the majority 

 of the grains is 73° to 74° C, and of all is 77° to 

 78° C, mean 77.5° C. 



Effects op Various Reagents. 

 The reaction with chloral hydrate begins in rare 

 grains in 2 minutes. Complete gelatinization occurs in 



less than 0.5 per cent of the entire number of grains and 

 total starch in 5 minutes; in about 3 per cent of the 

 grains and 6 per cent of the total starch in 15 minutes; 

 in about 16 per cent of the grains and 24 per cent of the 

 total starch in 30 minutes; in about 20 per cent of the 

 grains and 28 per cent of the total starch in 45 minutes ; 

 in about 27 per cent of the grains and 34 per cent of the 

 total starch in 60 minutes. (Chart D 259.) 



The Jiilum is not distinct, except in a rather large 

 minority of the grains in which a small bubble is formed, 

 which remains unchanged until the reaction is nearly 

 completed. The lamella? are at first indistinct, but grad- 

 ually become moderately distinct in most of the grains. 

 The grains grow somewhat more refractive in appearance 

 after the addition of the reagent, and the first part to 

 show the increased refractivity is a rather narrow band 

 of starch at the margin of the grains. Gelatinization 

 in all the grains, except those which are lenticular in 

 shape, begins at various points, usually the ends of pro- 

 tuberances on the distal margin, and from these points 

 extends to two or three marginal lamellae which have 

 been separated from the rest of the grain, except a small 

 portion at the proximal end. The rest of the grain 

 now assumes a pitted appearance and, as gelatinization 

 proceeds inward, is invaded by fissures which separate 

 granules from the ungelatinized starch. In this man- 

 ner gelatinization progresses until the hilum is reached, 

 the bubble first swells, then shrinks, and finally dis- 

 appears, and the hilum swells and the material at the 

 proximal end which is the last to react is quickly gela- 

 tinized. The lenticular grains are first divided into two 

 parts by a broad refractive fissure in the long axis of the 

 grain and then gelatinization begins at the margin at 

 cither end of this fissure and proceeds smoothly toward 

 the center, in which is the hilum. When this is reached 

 the hilum swells suddenly and the hitherto ungela- 

 nized portion immediately surrounding it is quickly 

 gelatinized. 



The gelatinized grains are much swollen and have 

 moderately thin capsules. They are very much distorted 

 and do not retain any resemblance to the form of the 

 untreated grain. 



The reaction with chromic acid begins in 1 minute. 

 Complete gelatinization occurs in less than 0.5 per cent 

 of the entire number of grains and 7 per cent of the total 

 starch in 5 minutes; in less than 0.5 per cent of the 

 grains and 65 per cent of the total starch in 15 minutes ; 

 in about 27 per cent of the grains and 80 per cent of 

 the total starch in 30 minutes; in about 44 per cent of 

 the grains and 95 per cent of the total starch in 45 min- 

 utes ; in about 60 per cent of the grains and 98 per cent 

 of the total starch in 60 minutes.* (Chart D 260.) 



*This reagent gelatinizes the mesial portion much more rapidly 

 than the margin, as is very generally the case with starches with 

 this reagent. The margin is much more resistant in some grains 

 than in others, hence the differentiation of the starches is much 

 more marked in the percentage of complete gelatinization than in 

 the total gelatinization. The amount of starch at the margin varies 

 considerably in different grains; this represents one-third, one-fourth, 

 one-fifth to about one-twentieth of the entire grain, and hence, while 

 in some starches the percentage of the grains gelatinized is quite low, 

 that of the total starch is high. There was found to be such a 

 difference in the complete gelatinization of JV. pociicua oryialus and 

 the other members of this set that the experiments with this re- 

 agent were repeated with practically absolutely identical results. 



