REACTION-INTENSITIES WITH EACH AGENT AND REAGENT. 



169 



A given starch may exhibit like or unlike reactions 

 with different reagents, and the curves vary as much as 

 do those of different starches with the same reagent, so 

 that there may be most varied forms of the different 

 types. This feature will be found to be well exhibited 

 when the curves of the reactions of any given starch of 

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

 stance, the curves of Amaryllis belladonna (Chart D 1 to 

 D21). The curve in the chloral-hydrate reaction is of 

 the / form, having an inclination of about 50°, so that 

 the upper end is 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 5 minutes the 

 percentage gelatinized in both reactions is practically 

 the same (12 and 10 per cent, respectively), that the 

 gain in the chromic-acid reaction occurs during the next 

 10 minutes; and that the quantities gelatinized during 

 the interval between 15 and 30 minutes are the same in 

 both reactions. The pyrogallic-acid and chloral-hydrate 

 curves bear 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 60 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 first 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, D 14, and 

 D16), in each of which about 98 per cent of the total 

 starch was gelatinized in 5 minutes. In the sodium- 

 sulphite reactions the increments of gelatinized starch 

 are 66, 14, 4, 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 18, and 

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

 parison vwth the foregoing. In the mercuric-chloride 

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

 fact, like the accompanying Brunsvigia josephince curve, 

 to be rectilinear, but at an angle of about 18° as com- 

 pared with about 26° for the latter. In the reactions of 

 nitric acid, sulphuric acid, hydrochloric acid, and potas- 

 sium hydroxide (Charts D4, D 5, D 6, and D 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 

 their 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 be found that there is or is 

 not relationship in the characters of the curves, and this 

 peculiarity may also apply to the curves of hybrids in 

 relation to those of its parents. For instance, taking 



the chloral-hydrate reactions : of the starches of Liliiim 

 (Charts D 347, D 354, D 367, and D 373) the concord- 

 ance of both type and type-form is obvious; of the 

 starches of Nerine (Charts D 190, D211, and D 232), 

 the curves of the five parental starches are of the / form, 

 but vary in their courses sufiiciently for easy differentia- 

 tion; of the starches of Crinum moorei, C. longifolium 

 and G. powellu compared with those of C. zei/lanicum, 

 where we have subgeneric or the equivalent of subgeneric 

 representatives (Charts D 127, D 148, and D 169), the 

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

 while the curve of the latter is of an entirely different 

 type; of the starches of Begonia, where similarly well- 

 separated starches are represented by those of the seed 

 parent on the one hand and by the starch of B. socotrana 

 (pollen parent) on the other (Charts D 463, D 527, 

 D533, and D539), the curves are closely similar; of 

 the starches of Amaryllis and Brunsvigia, where two 

 recognized genera are represented, the curves are much 

 alike (Chart Dl). Varieties that are offspring of 

 closely related parental stock, as in Hippeastrum (Charts 

 D 22, D 43, and D 64), tend to show marked closeness in 

 the curves and this may also be seen not only in closely 

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

 (Chart D421), but also in closely related genera, as in 

 Gladiolus and Tritonia (Charts D 463 and D484). The 

 curves of hybrids show, as will be pointed out particu- 

 larly hereafter, the most varied relationships to the 

 parental curves, varying between identity and great 

 dissimilarity. 



Taking the reactions of all of the parental starches 

 with any given reagent and comparing them with those 

 of other reagents, it becomes apparent that those of each 

 reagent represent a group in which there are both simi- 

 larities and dissimilarities ; and that the different groups 

 as such exhibit similarities and dissimilarities, the reac- 

 tions collectively of each group being quite as or even 

 more distinct from those of another group as 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 sometimes distantly 

 or whollj' unrelated starches may exhibit almost if not 

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

 peculiarities of these reactions are of such characters 

 as should logically be expected if we are dealing with 

 stereoisomerie forms of starch. 



The starches of the hybrid and parents usually take on 

 within a brief period after the beginning of gelatinization 

 definite relationships, which may be the same or different 

 in the reactions with different reagents. That is, if 

 shortly after the beginning of the reaction the positions 

 of the three curves should be in the order of intensity 

 of reactivity, seed parent, pollen parent, and hybrid (high- 

 est, intermediate, and lowest), this relationship usually 

 tends to be continued during the entire period of gela- 

 tinization, but with varying degrees of separation of the 

 curves. The hybrid curve may bear any relationship 

 to one or the other or both parental curves — ^that is, be 

 higher or lower than either, or intermediate, or the same 

 as one or the other or both. lUirely the parental curves 

 cross (Chart D169), or the hybrid curve crosses one 

 or the other parental curve (Chart D 89). The hybrid 

 curves tend usually to follow closely the parental curves, 

 but they may differ as much or more from the parental 



