PREFATORY NOTES. V 



that the erratic form of the Dieffenhachia grain is an expression more of differences 

 in incidental conditions than of the constitution of the plastids and the starch. 



It will also be noticed that in a given family, such as Iridacece, there may be 

 represented among the various genera many entirely different types of starch- 

 grains, with generally corresponding differences in the types of the reaction curves, 

 as is represented for instance in Iris (plates 63 to 67, figs. 373 to 397, chart 303) 

 and Freesia (plate 73, figs. 433 and 435, chart 310), in which both histological and 

 reaction types indicate an absence of generic relationship and suggest that Freesia 

 should not be classed with Iris (see Chapter VIII, page 340). Such instances as 

 the latter are of frequent occurrence, not only among Iridacece but also throughout 

 the research. Owing to the generally tentative character of botanical classification 

 and the very limited range and preliminary nature of this research further con- 

 sideration of the problem of correct classification must be postponed. 



QUANTITATIVE AND QUALITATIVE METHODS. 



The methods used in this investigation are both quantitative and qualitative, 

 and in effect chiefly the former, although considerable and even disproportionate 

 time and space have been given to the latter. The greater importance associated 

 with the quantitative side is, however, not to be taken as a measure of its relative 

 value, but as an indication of conditions which at the inception of the work misled 

 to the belief that comparatively Uttle was to be gained by the strictly qualitative 

 method unless the studies were carried out to a degree of refinement that seemed 

 absolutely prohibitory in a preliminary investigation of such scope as that of the 

 present. In all of the experiments, except a few with the latest starches studied, 

 very little attention was given to qualitative phenomena beyond the grossest 

 kinds of observations, and even in the latter really not more than is sufficient to 

 indicate how much is available by detailed examinations. Thus, in comparing 

 the records generally with those of the group made by Miss Bunting (which repre- 

 sent the later work) it will be found that phenomena are recorded in the latter 

 which have not had corresponding notice in the former. Subsequent to the com- 

 pletion of this report investigations have been made with a number of starches 

 in very much more detail, especially with starches from closely related species 

 and varieties, and particularly with the chemical reagents, with the result of find- 

 ing qualitative variations which often are of considerable importance, especially 

 in the differentiation and grouping of members of a genus. 



In the studies of each genus the qualitative reactions of each reagent with 

 one representative of that genus was taken as a type, and when the term "quali- 

 tatively the same," or a synonymous expression, is recorded it is intended to sig- 

 nify that the reactions qualitatively are of the same generic type, and not to imply 

 that there are not finer differences that may be expressive of individuahties of 

 species and varieties. In fact, as intimated, such differences can in most cases 

 be made out without difficulty, and oftentimes of a surprisingly distinctive char- 



