REACTION-INTENSITIES Willi EACH AGENT AND REAGEN] 



L69 



A given starch may exhibit like or unlike reai I 

 with different reagents, and the curves vary as mm 

 do those of different starches with the same reagent, so 

 that there may be mo I varied forms of the different 

 Tins feature will be found to be well exhibited 

 when the curves of the reactions of am given starch of 

 any one of the generic groups are compared, for in- 

 stance, the curves of Amaryllis belladonna (Chart 1> l to 

 D?l). The curve in the chloral-hydrate reactio is of 

 the f form, having an inclination of about 50 , so thai 

 the upper end i- at the termination of the 60-minute 

 interval. The curve of the chromic-acid reaction is of 

 the / form, but it. terminates at the end of the 30-minute 

 interval, giving it an inclination of about 30°, which 

 indicates a very much more rapid gelatinization. It will 

 be seen, however, that during the first '< minutes the 

 percentage gelatinized in both reactions is practically 

 the -am.' (12 am! Hi pci' cent, respectively), that the 

 gain in the chromic-acid reaction occurs during the next 

 Hi minutes; and that the quantities gelatinized during 

 tin" interval between L5 ami 30 minutes are the same in 

 both reactions. The pyrogallic-acid and chloral-hydrate 

 curves hear a close resemblance; but the former is lower 

 throughout, especially at the end of the 5-minute inter- 

 val, indicating a more marked early resistance to this 

 reagent than to chloral hydrate. From this point on- 

 ward to the end of till minutes the curves run Very closely 

 parallel. 



In 11 of the 21 experiments with different reagents 

 the curves belong to the form of circumlinear type that 

 is characterized by progressively decreasing increments of 

 starch gelatinized during additional increments of time. 

 These curves vary markedly in character. In some the 

 increment of starch gelatinized during the fust 5 minutes 

 is very disproportionate to the quantities subsequently 

 broken down, as is noted particularly in the reactions of 

 potassium sulphide, sodium hydroxide, calcium nitrate, 

 and strontium nitrate (Charts D 10, D 11, DM, and 

 D16), in each of which about OS per cent of the total 

 starch was gelatinized in 5 minutes. In the sodium- 

 sulphite reactions the increments of gelatinized starch 

 are lid, 1 1. 1, 3, and 2 per cent. In the other reactions 

 of this group, including those of potassium iodide, so- 

 dium salicylate, uranium nitrate, copper nitrate, and 

 cupric chloride (Charts D 8, D 13, D 15, D is, and 

 1)19), the curves exhibit various modifications in com- 

 parison with the foregoing. In the mercuric-chloride 

 reactions the curve is of a modified / form, tending, in 

 fact, like the accompanying Brunsvigia josephinai curve, 

 to he rectilinear, hut at an angle of about 18 c as com- 

 pared with about 26° for the latter. In the reaction- of 

 nitric acid, sulphuric acid, hydrochloric acid, and potas 

 sium hydroxide (Chart- D 1. D 5, D 6, and 1)7), the 

 curve is rectilinear and almost vertical, while in the 

 barium-chloride reactions (Chart D 20) it is rectilinear 

 and almost horizontal. 



Starches of members of a genus tend, as a rule, in 

 then- reactions with each reagent to yield curves that are 

 of or incline to the same type and type form, except when 

 there are subgeneric representatives or widely separated 

 species, in which case it may he found that there is or is 

 not relationship in the characters of the curves, an 

 peculiarity may also apply to the curves of hybrids in 

 relation to those of its parents. For instance, taking 



■ he i bloral hydi : of the 



(Charts 1» :;i". . D 35 :. I) 367, and D 373) th 

 ance of C and type form is obvious ; of 



starches of Nerim (( harts D 190, I) 211, and h 

 the curve of the five parental starches are of the/ I 

 hut vary in their courses sufficiently for easy differentia- 

 tion; of th.' starch.- of < ■ C. longifolium 

 and ( mpared with those of ( cum, 

 i'hi re we have subgeneric or the i neric 

 representatives (( han D 127, D I 18, and D L69), the 

 curves of the first three conform to a given type-form, 

 while the curve of the latter is of an entirely dill. 

 type; of the starches of Begonia, where similarly 

 separated starches are represented \,y those of the seed 

 parent on the one hand and by the starch of /•'. 

 (pollen parent) on the other (Charts \> 163, 1' 

 D 533, and D539), the curve- are close! ii; of 

 the starches of Amaryllis and Brui 

 recognized genera are represented, the i m 

 alike (('hart D 1). Varieties that are oti'sprit. 

 closely related parental stock, as in Hippeastrum (Charts 

 D 22, D 43, and D 64), tend to show marked clo 

 the curves and this may also he seen not only in cl 

 related species, as in Phaius (Chart D 574) and Iris 

 (Chart D421 ), hut also in closely relate ' as in 

 Gladiolus and THtonia ((hart- D463and D484). 1 

 ciirws of hybrids show, as will he po uted out | articu- 

 larly hereafter, the most varied relationships to the 

 parental curves, varying between identity and great 

 dissimilarity. 



Taking the reactions of all of the parent;! 1 

 with any given reagent and comparing them with those 

 of other reagents, it becomes apparent that those of cadi 

 reagent represent a group in which there are both -inn 

 larities and dissimilarities ; and that the different groups 

 as such exhibit similarities and dissimilarities, 

 tions collectively of each group being quite as or even 

 more distinct from those of another group a- are those 

 of members of the same group; that the more closely 

 related the starches the more marked the tendency gener- 

 ally to closeness of the curves, yet sometime 

 or wholly unrelated starches may exhibit almost if not 

 identical curves with a given reagent. In a word, the 

 peculiarities of these reactions are of such 

 as should logically be expected if we arc dealing with 

 stereoisomers forms of starch. 



The starches of the hybrid and parents usuallj take on 

 within a brief period after t he beginning of gelatini: 

 definite n hit ion -hips, which ma\ he the same or differei t 

 in the reactions with different reagents. That is. if 

 shortly after the beginning of the reaction the positions 

 of the three curves should he in the order of irtti 



of react i\ ity, s I parent, pollen parent, and hybi 1 1 



est, intermediate, and lowest), this relationship usually 

 tends to be continued during the entire period of 

 tinization, but with /arying degrees of separation of the 

 curves. The hybrid curve may hen- any r. 

 to one or (he other or both parental curves that 



■r or lower than either, or intermediate, or the same 



a- r the other or both. Rarely the parental curves 



cross (Chart D169), or the hybrid cur 



or the other parental curve (Chart I'M'). The 1 



curves tend usually to follow closely t 



but they may differ as much or more from th 



