BEGONIA. 



697 



EFFECTS OF VARIOUS REAGENTS. 



The reaction with chloral hydrate begins immediately. 

 Complete gelatinization occurs in about 81 per cent of 

 the entire number of grains and 88 per cent of the 

 total starch in 5 minutes; in more than 99 per cent of 

 the grains and total starch in 10 minutes. (Chart 

 D505.) 



The hilum becomes rather indistinct in all the grains, 

 unattended by the formation of a bubble in any. The 

 lamella? are not visible. The grain grows more refractive 

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

 grain to show this change is a rather narrow band of 

 starch at the margin which becomes somewhat more 

 refractive but not very much. Gelatinization begins 

 at the distal margin at 1 or 2 discrete points which are 

 first invaded by small cracks, and from these points it 

 spreads over the whole distal margin, and then rapidly 

 toward the proximal end, and usually more rapidly 

 around the margin than in the center of the grain. The 

 last part of the grain to be gelatinized is immediately 

 surrounding the hilum, and as the hilum swells this 

 usually is split into 2 or 3 pieces, which are widely 

 separated and gelatinized independently of one another. 



The gelatinized grains are much swollen, have moder- 

 ately thick capsules, and considerably distorted. 



Comparison of the chloral hydrate reactions between 

 B. socotrana and B. single crimson scarlet shows: 



The hilum is invisible, as are also the lamella?. The 

 grains become somewhat more refractive after the addi- 

 tion of the reagent than in B. single crimson scarlet. 

 Gelatinization, as in the latter, begins at 2 or 3 discrete 

 points on the margin and in the majority of the grains 

 proceeds as in B. single crimson scarlet, except that the 

 starch at the proximal margin is the last portion of 

 the grain to be gelatinized instead of that immediately 

 surrounding the hilum. In some of the grains the proxi- 

 mal end is gelatinized immediately after the distal end 

 and the last part to be gelatinized is that midway be- 

 tween the hilum and the distal end. This method is 

 not seen in B. single crimson scarlet. The gelatinized 

 grains are as much swollen and more distorted than in 

 B. single crimson scarlet, and have thin rather than thick 

 capsules. 



The reaction with chromic acid begins immediately. 

 Complete gclatinization occurs in about 44 per cent of 

 the entire number of grains and 85 per cent of the total 

 starch in 5 minutes ; in about 64 per cent of the grains 

 and 98 per cent of the total starch in 15 minutes. (Chart 

 D506.) 



Experiment repeated, showing 45 per cent of grains 

 and 86 per cent of total starch in 5 minutes. 



General Notes on Chromic Acid. The time reactions with 

 chromic acid are difficult to obtain with positive accuracy 

 because there is a tendency for bubbles to appear in the solu- 

 tion, which may break, and either carry the grains under 

 observation away from the field or force in new ones. Since 

 there is considerable solution of all or a large part of some 

 grains in all species with the exception of B. socotrana, when 

 the number in the field changes because of the above-stated 

 causes, it is impossible to be certain as to the original number 

 of grains which were present at the beginning of the reaction. 

 When changes are detected, and there is any considerable addi- 

 tion or subtraction, a new preparation must be made; and 

 unless the preparation is constantly under observation, slight 

 changes from shifting may occur, and hence to obtain a con- 

 stant many observations should be made and an average per- 

 21 



centage computed. In other experiments with Begonia starches 

 in which the percentages at 5 minutes have appeared to be 

 abnormally high, as in B. double white, the experiments have 

 been repeated with practically identical results. With the 

 latter starch the first experiment gave 75 per cent of the 

 grains and 97 per cent! of the total starch in 5 minutes, and 

 the second experiment 75 per cent of the grains and 96 per 

 cent of the total starch. The number of grains under 

 observation in the first was 200 and in the second 140. These 

 experiments were made on consecutive days. 



It will be noted in these experiments that B. socotrana 

 is very much slower in its time-reactions than all the other 

 specimens, and that, while the hybrid more closely follows those 

 of the seed parent, the influence of B. socotrana appears marked 

 at the 5-minute observation in all these starches with the excep- 

 tion of B. success. The time reactions at 5 minutes were re- 

 peated with B. double deep rose and B. success in order to test 

 the possibility of the number of grains changing because of the 

 shifting above mentioned during the reaction, but the resulting 

 percentages obtained were practically the same. (See note, 

 page 705.) 



The hilum becomes distinct in all the grains, un- 

 attended by the formation of a bubble in any. The 

 lamellse are indistinct or invisible. Gelatinization begins 

 at the hilum which swells rapidly and more in the direc- 

 tion of the proximal than of the distal end. Two fissures 

 are seen in many grains extending from either side of the 

 hilum about half the distance between the hilum and the 

 distal end, and the starch comprehended between them 

 is usually gelatinized without any fissuring or granule 

 formation. The resistant starch at the margin forms a 

 thick* homogeneous-looking band which is thicker at 

 the distal than at the proximal margin; this grows 

 thinner and more refractive and is dissolved at the proxi- 

 mal end. Toward the end of the reaction the rest of the 

 marginal band may be separated into 2 layers which 

 dissolve separately. 



Comparison of the chromic-acid reactions between 

 B. socotrana and B. single crimson scarlet shows: 



The hilum is as distinct as in B. single crimson scar- 

 let, and the lamellae are visible in all the grains, and 

 usually very distinct. Gelatinization begins at the hilum 

 which only swells slightly, instead of rapidly, and only 

 somewhat more in the direction of the proximal than of 

 the distal end. Two fissures extend from either side of 

 the hilum, and the starch comprehended between them 

 and immediately distal to the hilum is quickly divided by 

 two rows of slanting fissures. This phenomenon is never 

 seen in B. single crimson scarlet, the grain remains so 

 without further change, except that it grows more re- 

 fractive and is gradually divided into an outer homo- 

 geneous-looking layer and an inner granular mass. The 

 outer layer is divided at one corner of the distal end and 

 in some grains splits away from the inner granular por- 

 tion which may or may not be dissolved first. 



The reaction with pyrogallic acid begins immediately. 

 Complete gelatinization occurs in about 16 per cent of 

 the entire number of grains and 58 per cent of the total 

 starch in 5 minutes ; in about 50 per cent of the grains 

 and 88 per cent of the total starch in 15 minutes ; in 

 about 58 per cent of the grains and 92 per cent of the 

 total starch in 30 minutes; in about 66 per cent of the 

 grains and 95 per cent of the total starch in 45 minutes ; 

 in about the same percentage of the grains and 97 per 

 cent of the total starch in 60 minutes. (Charts D 507 

 and D508.) 



The hilum becomes distinct in all the grains, unat- 

 tended by the formation of a bubble in any. The lamella? 



