REACTION-INTENSITIES WITH EACH AGENT AND REAGENT. 



167 



reagent; that the reactions of a given starch may vary 

 with different agents and reagents within wide limits; 

 that there is a manifest tendency to groupings of reac- 

 tion-intensities of different starches that are, on the 

 whole, very closely in harmony with the plant groupings 

 of the systematist; that the most variable relationships 

 exist between the starches in their reaction-intensities, 

 as regards sameness, intermediateness, excess and delicit 

 of reaction-intensity development of the hybrid in rela- 

 tion to the reactions of the parents ; and that the differ- 

 ences in the reactions are conditioned by differences of the 

 starch molecule, by the characters of the agents, and by 

 molecular constitution and concentration of the reagents. 

 The comparative studies of the reactions with the chemi- 

 cal reagents have as their sole basis values that are ex- 

 pressed in terms of percentage of starch gelatinized in 

 60 minutes or less. There was no note regarding dif- 

 ferences that were recorded in the comparative percent- 

 ages, of the entire number of grains and total starch 

 gelatinized at definite time-intervals, and only the most 

 casual references were made to peculiarities observed 

 in the progress of curves of the reactions from period 

 to period ; yet both of these features are found to be of 

 great importance, alone and in conjunction with the 

 findings presented in the foregoing sections, in the de- 

 termination of generic, species, varietal, parental, and 

 hybrid peculiarities of starches. The reaction-intensi- 

 ties of different starches with different reagents recorded 

 in Part II, Chapter I, include the percentages of both 

 the entire grains and total starch gelatinized at definite 

 time-intervals. The data of the total starch gelatinized 

 have been tabulated in Section 3 of each of the Compari- 

 sons of the Starches of the Parent- and Hybrid-Stocks 

 in Chapter III, and they are here presented with few 

 unimportant exceptions in the form of Charts D 1 to 

 D 634 which admirably exhibit both intensity and 

 progress of the reactions, and render comparisons of the 

 behavior of both starches and reagents very satisfactory. 

 Additional charts (Charts D 635 to D691) have been 

 introduced to show the relationships between the per- 

 centages of entire grains and total starch gelatinized at 

 given time-intervals. There will also be found among 

 Narcissus, Lilium, and Begonia a few charts that show 

 differences between these percentages, and a few addi- 

 tional charts to bring out certain generic peculiarities. 



These charts are so very numerous and the curves so 

 exceedingly varied that detailed descriptions and com- 

 parisons are rendered impracticable because of necessary 

 limitations of space, although it will be perfectly mani- 

 fest, after even a superficial survey, that the results of 

 such a study would prove of great value in many direc- 

 tions ; yet very much that is of more than mere passing 

 interest, value and suggestiveness can be brought out by 

 even casual examination. 



PERCENTAGE OF TOTAL STARCH GELATINIZED AT 

 DEFINITE TIME-INTERVALS. 



(Charts D 1 to D 634.) 



The curves of total starch gelatinized vary widely 

 and the number and forms of types recognized are purely 

 arbitrary. In some instances the curve is nearly or 

 absolutely rectilinear, but in most cases it is circumlintar 

 and varied, but suggestive usually of an ellipse, hyperbola 



or parabola or some modification of one of the three. 

 The rectilinear curves are presented in the form of three 

 types or what may tentatively be regarded as three modifi- 

 cations or forms of a single type : 



(a) A form that is characterized by an immediate, 

 very rapid and continually rapid rise of the curve at an 

 angle approximating about 1 to 2 with the verti- 

 cal, thus representing a complete or practically com- 

 plete gelatinization in 1 or 2 minutes. This curve 

 should probably be circumliuear inasmuch as it is likely 

 that during equal increments of time larger increments 

 of the starch are gelatinized during the earlier than later 

 periods of the reactions, but the time-intervals here are 

 too short for such determinations. This belief is sup- 

 ported by the fact that when the reactions of the same 

 starch but with a weakened reagent are somewhat less 

 rapid, as when complete gelatinization occurs at the end 

 of 5 minutes, this variation is noted and the circumlinear 

 character of the curve is quite marked, the increments 

 of gelatinized starch falling very rapidly and dispro- 

 portionately after the first minute. This form of curve 

 is illustrated in the Amaryllis-Brunsvigia-Brunsdonna 

 group in the reactions with nitric acid, sulphuric acid, 

 hydrochloric acid, and potassium hydroxide (Charts D 4, 

 D 5, D 6, and D 7). It will be seen that in some of the 

 reactions the line is straight and in others curved. 



(&) Another form of the rectilinear type presents a 

 curve that is almost if not entirely rectilinear, but having 

 an inclination that rarely is less than an angle of 80 U 

 with the vertical, which is equivalent to a maximum of 

 approximately 15 per cent of the total starch gelatinized 

 in 60 minutes. This form of curve is associated usually 

 with weak gelatinizing reagents and exceptionally re- 

 sistant starches. It will very frequently be found in the 

 study of these charts that while a given starch may show 

 such a curve with one reagent, a curve of the first form 

 or of an entirely different type may be exhibited with 

 another reagent. Such a curve is well typified in the reac- 

 tions of Brunsdonna sanderos alba with sodium sulphide, 

 cobalt nitrate, cupric chloride, barium chloride, and mer- 

 curic chloride (Charts D 12, D 17, D 19, D 20, D 21). 



(r) A third form of the rectilinear curve links in its 

 varied positions the first and third forms, and were it not 

 that the first two forms are very common and the third 

 form relatively rare, there would be no good reason for 

 the recognition of three forms. This form is illustrated 

 in the reactions of Brunsvigia josephina with mercuric 

 chloride (Chart D21), of Crinum Jcircape with sodium 

 sulphide (Chart D 1 159), and of Nerine bowdeni with 

 uranium nitrate (Chart D 225). 



The circumlinear type of curves is divisible into three 

 forms : 



(a) One form shows that gelatinization begins and 

 proceeds rapidly, there being progressively or practically 

 progressively decreasing increments of starch gelatinized 

 with additional increments of time. This form is illus- 

 trated in the reactions of Amaryllis belladonna with 

 sodium sulphide (Chart D12). This form of curve is 

 very common, perhaps the most common of all. An 

 examination of this series of charts ( Charts D 1 to 

 D 634) will elicit most varied and modified gradations in 

 both directions from what may properly be regarded as 

 a true hyperbolic form. 



