170 



REACTION-INTENSITIES OF STARCHES. 



curves as do the latter from each other (Charts D 241, 

 D 277, and D 343). When there are two hybrids of the 

 same parentage, the curves may differ quite as much or 

 more i'rom each other, as the parental curves dili'er from 

 each other. (Charts D 1 to D 21.) 



PERCENTAGES OF TOTAL STARCH AND ENTIRE NUMBER 



OF GRAINS GELATINIZED AT DEFINITE 



TIME-INTERVALS. 



(Charts D 635 to D 688; also D 261, D 268, D 290, D 296, D 302, 

 D 308, D 314, D 320, U 326, D 332, D 338, D 344, D 350, D 351, 

 D 357, D 365, D 366, D 508, D 530, D 530, D 542.) 



The curves of the percentages of total starch and the 

 entire number of grams completely gelatinized tend in 

 general to correspond in their courses; but both may 

 differ in varying ways, relatively and absolutely, in 

 accordance with the kind of starch and the reagent, 

 excepting, of course, when the reactions, are too fast 

 or too slow for definite differentiation. 



When starch is gelatinized it passes into an imperfect 

 or pseudo-solution, and the grains, like solid particles 

 or masses of other substances passing into solution, show 

 differences in solubility of both grains in their entirety 

 and parts of individual grains. Some grains may 

 undergo complete gelatinizatiou, while others do not 

 exhibit any obvious change ; and other grains show very 

 variable proportions that have undergone a breaking- 

 down. These peculiarities have been observed in all 

 kinds of starch with the same reagent. They are con- 

 stant for the same starch with the same reagent ; variable 

 with the same starch with diiferent reagents; and variable 

 with different starches with the same reagent. The 

 behavior of each starch with the different reagents is, as 

 a whole, so characteristic and specific as to be diagnostic. 

 These several points will be found to be well illustrated 

 if there be taken a number of starches that are represen- 

 tative of different generic and subgeneric divisions, plot- 

 ting in curves the data of the reactions of one of the 

 starches with one reagent, and supplementing this group 

 with curves of the reactions of a few arbitrarily selected 

 starches with several reagents. Thus, taking the pyro- 

 gallic-acid reactions (Charts D 635 to DG-19), it will 

 be found that the curves of the percentages of total starch 

 and the entire number of grains completely gelatinized 

 differ widely; that the two curves of each starch tend 

 in general to correspondence in their courses; that the 

 degree of correspondence varies from marked closeness 

 to an almost lack of any likeness; and that the degree 

 of separation of the curves varies in the different starches 

 and also during the progress of the reactions. It is 

 obvious that the farther the separation of the curves 

 the smaller relatively the percentage of the entire num- 

 ber of grains completely gelatinized, and the higher rela- 

 tively the proportion of the total starch gelatinized in 

 the partially gelatinized grains. 



In some of the starches it will be seen that during 

 the progress of the reactions the increasing height of the 

 curve of the percentage of total starch gelatinized is 

 almost if not directly proportional to the increase in 

 percentage of the entire number of grains completely 

 gelatinized in other words, the total per cent gela- 

 tinized is not appreciably or but little contributed to by 

 the amount of gelatinization in grains that have under- 

 gone only varying degrees of partial disorganization; in 



others, there will be found the reverse, the major por- 

 tion of the percentage of total starch gelatinized being 

 yielded by grains that have been only in part, but to vary- 

 ing degrees, broken down; in others, there are various 

 gradations between the former. These peculiarities are 

 constant with each starch with each reagent, except in 

 very rare instances, indicating thereby that they are in 

 part expressions of inherent constitutional properties 

 of starch molecules that differ in accordance with the 

 plant source. In reactions that are completed within 2 to 

 5 minutes or so, or which are so slow that a very small 

 percentage of the starch is gelatinized by the end of 60 

 minutes, the differences between the two percentages 

 may be so small as to be undetectable, or if detectable 

 of little or no value in demonstrating this peculiarity. 

 This is found, for instance, in Lilium tcnuifolium (Chart 

 D 644), 99 per cent of the total starch is gelatinized in 5 

 minutes, 93 of this 99 per cent being contributed by grains 

 completely gelatinized and the remaining 6 per cent of 

 grains being only partially gelatinized, and 1 per cent 

 unaffected. Additional instances are found, but in the 

 opposite direction, in the reactions of Hwmanthus katlier- 

 ince (Chart D639), Iris iberica (Chart D684), and 

 liicliardia albo-maculata (Chart D 652). 



Taking, in turn for comparative purposes, several 

 selected charts of this series, and beginning with those 

 of LiUum tenuifolium (Chart D 644) and Hcemanthus 

 katherince (Chart D639), which represent opposite ex- 

 tremes of reaction-intensities, and wherein the two per- 

 centage curves in each are almost identical, variations 

 in the courses of these curves will be found that are 

 coupled with variations in the degree of separation of 

 the curves during the progress of reactions, each chart 

 being in one or both respects different from the other 

 charts, and therefore characteristic of starch plus rea- 

 gent. In Cymbidiwn lowianum (Chart D 657) the reac- 

 tions occur rapidly, gelatinization being practically 

 complete in 15 minutes, 98 per cent of the total starch 

 being gelatinized in 5 minutes, of which quantity 87 

 was made up of the starch of completely gelatinized 

 grains; while in Richwrdia albo-maculata only 11 

 per cent of the total starch was gelatinized in 60 

 minutes, of which quantity 6 per cent was made 

 up of the starch of grains completely gelatinized. In 

 some of the other charts gelatinization is shown to pro- 

 ceed with fair to moderate activity, but during the earlier 

 part of the 60-minute period the proportion of gelatinized 

 starch contributed by grains that are entirely broken 

 down is decidedly less than that by the partially gela- 

 tinized grains. This peculiarity is well illustrated, for 

 instance, in Iris iberica (Chart D 646), Iris tro- 

 jana (Chart D647), and Phaius grandifolius (Chart 

 D655). In Iris iberica, at the end of 5-minute 

 period, 20 per cent of the total starch was gelatinized, 

 of which quantity only 2 per cent was contributed by 

 grains that were entirely gelatinized; at 15 minutes the 

 figures are 62 and 30, respectively; at 30 minutes, 81 

 and 42, respectively; at 45 minutes, 86 and 53, respec- 

 tively ; and at 60 minutes, 54 and 90, respectively. Simi- 

 lar data are recorded in the other two charts, the 

 proportions in each varying at the different periods 

 at the end of 60 minutes, in 7m iberica, 54 : 70, in I. tro- 

 jana, 63: 96, and in Phaius grandifolius, 28: 67, of the 

 gelatinized starch was contributed by the grains that 



