NOTES AND CONCLUSIONS. 



371 



are the same but modified in their applications in certain 

 important respects. In both investigations the histo- 

 logic properties, the iodine and aniline reactions, and 

 the gelatinization reactions with heat and various chemi- 

 cal reagents were studied, the chief differences being 

 in the method of recording the reactions with the chemi- 

 cal reagents, and in the kinds and concentrations of the 

 reagents. In the former research the quantitative dif- 

 ferentiations by means of the chemical reagents were 

 made by determining the time of the occurrence of com- 

 plete or practically complete gelatinization, and the 

 preparations of starch with the reagent were not ade- 

 quately protected from the air and evaporation. It was 

 found during the progress of this work that fictitious 

 values may be recorded owing to the existence in nearly 

 every form of starch of different kinds of grains which 

 vary in proportions and gelatinizabilities, together with 

 varying degrees of infiuence of the air (probably chiefly 

 or solely differences in oxidation), and effects that are 

 due to varying rapidi'ty and degrees of evaporation. 

 Such sources of fallacy have been practically eliminated 

 in the present research by making records of the progress 

 of gelatinization in regard to both the entire number of 

 grains completely gelatinized and the percentage of the 

 total starch gelatinized at definite time-intervals; and 

 by the prevention of oxidation and evaporation by seal- 

 ing the preparations. In nearly every form of starch 

 there are grains, usually very small, and also parts of 

 grains, that are quite resistant to reagents. The former 

 commonly represent much less than 5 per cent of the 

 total quantity of starch, and it has been assumed that 

 gelatinization is practically complete when 95 per cent of 

 the total starch has been gelatinized. The methods used 

 and their values in the differentiation of starches have 

 been set forth in full in the preceding memoir on pages 

 305 to 313, and supplementary statements are to be 

 found in the present memoir in Chapters II, IV, and V. 



The histologic method employed in this research is 

 the same in all respects as in the preceding investigation, 

 in the report of which it has been discussed with suffi- 

 cient fulness (page 307) . Its value has not only been sub- 

 stantiated but accentuated by the results of the present 

 study of the starches of parent- and hybrid-stocks. 



The polariscopic, iodine, and aniline methods are so 

 crude that the personal equation enters largely into the 

 determination of the values recorded, and while they 

 have proved of unquestionable usefulness they are so 

 inferior to the gelatinization method that they should 

 be given a very subordinate place. The polarization and 

 aniline mlethods are by far the least useful of all of those 

 used, yet the anilines will be found of much value in the 

 differentiation of different lamellse of individual grains, 

 as has been shown by the work of Denniston (see pre- 

 vious Memoir, page 56). lodiije, like the anilines, can 

 be used to great advantage in the study of the structure 

 of the starch grain. It is also of usefulness by showing 

 by variations in the color reactions differences in the 

 constitution of starches from different sources; of dif- 

 ferent kinds of grains of the same starch ; of the capsular 

 and intracapsular parts of the grains; and of the cap- 

 sules themselves. The method used in determining the 

 temperature of gelatinization is practically exact, as has 

 been shown by the fact that when the experiments are 

 made with proper care the figures recorded are quite as 



uniform as those obtained in the determination of the 

 melting-points of various substances. 



The gelatinization method by means of various 

 chemical reagents as here pursued has proven to be so 

 near exact that the records of repeated experiments 

 have, except very rarely, been found to be exactly or prac- 

 tically exactly the same, even though made at widely 

 different periods and with varying temperature and 

 humidity. Very rarely, for some inexplicable reason, a 

 more or less markedly aberrant record has been made. In 

 every instance this error was detected because of the 

 absence of agreement with what was positively indicated 

 by conditions. In fact, as was found in practice and as 

 will be obvious by the context, the records of the reactions 

 obtained by means of the various methods employed are 

 in the case of each agent and reagent, and of all collec- 

 tively, in a very large measure checks upon each other. 

 In other words, the values for the starch of a given spe- 

 cies serve as prototype or generic standard with which 

 the records of all other species and varieties of the genus 

 must conform, unless there are represented members 

 of subgenera or other subgeneric divisions. The closer 

 botanically the species or the varieties the closer will 

 the records collectively agree with the given standard. 

 Varieties of a species exhibit remarkable closeness, and 

 their values represent a species type. When members 

 of subgenera or other form of subgeneric division are 

 represented they may exhibit differences that are as 

 marked, and even more marked, than those of members 

 of closely related genera. 



It is to be borne in mind that the method of classi- 

 fication of the systematist is of an arbitrary character, 

 as is evident, for instance, in the shifting of species from 

 one to another genus, the remodeling of genera, families, 

 etc. This classifying and reclassifying that has been in 

 progress for generations continues at the present time, 

 and even now the most generally accepted classification 

 can not he accepted as being more than tentative. If, 

 therefore, the results of these investigations seem to be 

 or are not in accord in isolated instances with the classi- 

 fication of the systematist it does not follow that the 

 former are wrong. As evidence of the mutual checking 

 of the records one need examine only the very similar 

 curves of the starches of the closely related members of 

 7m (Charts B 30 to E 33) and Richardia (Chart E 40) ; 

 the dissimilar curves of the starches of members of 

 subgeneric divisions, such as the hardy and tender 

 species of Crinum (Charts B 7 to B9) ; the dissimilar 

 curves of the starches of members of subgenera of Be- 

 gonia (Charts B 36 to B 39) ; the similar curves of 

 the starches of the closely related genera Amaryllis and 

 Brunsvigia (Chart B 1), and of Gladiolus and Tritonia 

 (Charts E 34 and E35); and the dissimilar curves, 

 usually highly characterisi^c, of the starches of various 

 genera of the same and different families that are shovm 

 in this series of charts (B 1 to E 46), as a whole. These 

 similarities and dissimilarities are in degree variable in 

 accordance with what in general should be expected, or 

 what is at least in accord with unquestionable botanical 

 classification. 



The differentiation of starches by heat, as in the 

 temperature of gelatinization method, is to be recom- 

 mended as being of much value, both quantitatively and 

 qualitatively. It was shown in the preceding investi- 



