REACTION-INTENSITIES WITH EACH AGENT AND REAGENT. 



153 



very much higher sensitivity than the former; while 

 with potassium hydroxide there are three gradations of 

 sensitivity. The reactions of Iris persica var. purpurea 

 difEerentiate it from the first three members of this 

 genus. Another feature is seen in the very striking 

 differences in Begonia; in the first Begonia both reac- 

 tions are very high and the same, while in the second the 

 potassium-hydroxide reaction is similarly high and the 

 sodium-hydroxide reaction is low and far separated from 

 the former. 



Potassium sulphide and sodium sulphide (Chart 

 B 34) elicit reactions which as a whole are quite different 

 from those recorded in the preceding charts, but are 

 nevertheless in entire support of the fundamental pecu- 

 liarities that have been found to be set forth by the 

 reactions of each pair of reagents thus far studied — that 

 is, an independence of each reagent in its reactions that 

 is due to both concentration and kind of solute ; an inde- 

 pendence of the reactions of each starch that is dependent 

 upon differences in stereoisomeric forms; and an inde- 

 pendence of the course of each curve to such a degree 

 that there may not only be most variable quantitative 

 differences but also inversion, yet with a manifest ten- 

 dency to conforming with the peculiarities of a prototype 

 (say the nitric-acid curve). Probably the first feature 

 that will attract attention is the very marked differences 

 in the behaviors of Amaryllis and Brunsvigia with these 

 closely related reagents, the former exhibiting a very 

 high reactivity with potassium sulphide and a moderate 

 reactivity with sodium sulphide, thus showing a very 

 wide difference in reactivity, there being 97 per cent of 

 the total starch of Amaryllis gelatinized in 3 minutes 

 and only 91 per cent of the total starch of Brunsvigia 

 in 60 minutes; whereas with sodium sulphide the reac- 

 tivities of both starches are very nearly the same, 90 and 

 96 per cent, respectively, in 60 minutes being recorded, 

 Amaryllis throughout the course of the reaction showing 

 only slightly less reactivity than Brunsvigia. 



It will be noted that the two curves here are entirely 

 different from those of the three preceding charts (Charts 

 B 31, B 32, and B 33), which also so differ from each 

 other that each chart is very definitely individualized. 

 The reactions of the sulphides are the same or practically 

 the same in Brunsvigia josephince, Hippeastrum titan, 

 H. ossultan, Hmmwnthus josephince^ Crinum zeylanicum, 

 Lilium martagon, L. tenuifolium, L. chaJcedonicum, L. 

 pardalinum, and Begonia single crimson scarlet. The 

 potassium-sulphide reactions are higher in Amaryllis bel- 

 ladonna, HcBmanthu,s puniceus, Nerine crispa, N. how- 

 deni, N. sarrdensis var. corusca major. Begonia socotrana, 

 and Phaius grandifoliv^; and lower in Hippeastrum 

 dceones, Crinum moorei, G. longifolium, Napcissus tazetta 

 grand monarque. Iris iberica, I. trojana, I. cengialti, I. 

 persica var. purpurea. Gladiolus tristis, Tritonia pottsii, 

 and Miltonia vexillaria. For the most part the curves are 

 well separated, this feature being particularly accen- 

 tuated in Amaryllis belladonna, Crinum moorei, Nerine 

 crispa. Iris persica var. purpurea, and Begonia socotrana. 

 Hamanilius katherince and H. puniceus are not nearly 

 so well differentiated as in the preceding charts; the 

 hardy and tender Crinums are well differentiated, as 

 in the previous pairs of reactions. The Irids show nearly 

 the same reactivities with potassium sulphide, while three 



show nearly the same reactivities with sodium sulphide, 

 but higher than with potassium sulphide, and one a very 

 much higher reactivity than the first three with sodium 

 sulphide and a corresponding difference in relation to 

 potassium sulphide, showing a marked subgeneric sub- 

 division such as was noted with other reagents. In 

 Gladiolus and Tritonia the potassium-sulphide curves are 

 well below the sodium-sulphide curves, the difference in 

 each being about the same. In Begonia the differentia- 

 tion of the two starches is very striking. In Phadus and 

 Miltonia the generic differences are pronounced, not 

 only in regard to the degree of separation of the curves, 

 but also in respect to the inversion of the curves. The 

 high reactivities shown in Amaryllis belladonna, Nerine 

 crispa, and Begonia socotrana with potassium sulphide 

 in comparison with the moderate to very low reactivities 

 with the other reagent, together with the very opposite 

 in Crinum moorei. Iris persica var. purpurea, and Mil- 

 tonia bleuana, are striking manifestations of differences 

 in the molecular constitution of starches from different 

 plant sources. 



The reaction-intensities of potassiujn iodide and po- 

 tassium sulphocyanate (Chart B 35) present very much 

 closer relationships than do those of any of the pairs of 

 reagents thus far considered, yet here also are found 

 the fundamental peculiarities that have characterized all 

 of the comparisons brought out in the preceding charts. 

 The reactivities of these reagents are the same in Eceman- 

 thus hatherincB, Crinum moorei, C. zeylanicum, C. longi- 

 folium, Lilium martagon, L. tenuifolium, L. chalcedoni- 

 cum, L. pardalinum, and Begonia single crimson scarlet. 

 , The reactions of potassium iodide are higher than those 

 of potassium sulphocyanate in Amaryllis belladonna and 

 Brunsvigia josephince, and lower with all of the remain- 

 ing starches, except the group noted. The curves show 

 for the most part a marked concordance in their up- 

 and-down movements, but the degree of separation of 

 the curves is quite variable and there are inversions only 

 of Amaryllis and Brunsvigia. 



A comparative examination of the curves of the reac- 

 tions of sodium hydroxide and sodium salicylate (Chart 

 B 36) brings out one very exceptional feature that is 

 associated with the latter reagent, and various features 

 that are in harmony with characteristics that are com- 

 mon to the other charts. The marked limitations of the 

 reactions of sodium salicylate are most striking and 

 peculiar to this reagent. In only two reactions (those 

 with Crinum zeylanicum and Begonia single crimson 

 scarlet) is there a departure from the narrow limits of 

 the upper six abscissae (a trifle more than one-fourth 

 of the highest and lowest limits of reaction-intensities). 

 This limitation greatly restricts the value of the reagent 

 in the differentiation of starches from different plant 

 sources, yet there are in some instances marked to very 

 marked differentiation, especially of subgeneric groups. 

 The differences in the reactions of the two species of 

 Hcemanthus are not of themselves sufficient to definitely 

 indicate subgeneric division, but rather well-separated 

 species ; in Crinum the two hardy forms are well differ- 

 entiated from the tender form; in Iris the first three 

 stand definitely apart from the fourth; and in Begonia 

 there are striking differences between the two starches. 



