CHEMICAL BASIS OF PLANT FORMS 255 



tion of saponin in plants. The simpler compounds of which 

 this complex substance is built up, if located as compounds of 

 lower plants, would indicate the lines of progression from the 

 lower to the saponin groups. 



In my paper. 1 read in Buffalo at the last meeting of the 

 American Association for the Advancement of Science, vari- 

 ous suggestions were offered why chemical compounds should 

 be used as a means of botanical classification. 



The botanical classifications based upon morphology are 

 so frequently unsatisfactory, that efforts in some directions 

 have been made to introduce other methods. 2 



There has been comparatively little study of the chemical 

 principles of plants from a purely botanical view. It promises 

 to become a new field of research. 



The Leguminosae are conspicuous as furnishing us with im- 

 portant dyes, e. g., indigo, logwood, catechin. The former is 

 obtained principally from different species of the genus Indi- 

 gofera, and logwood from the H&matoxylon and Saraca indica. 



The discovery 3 of haematoxylin in the Saraca indica illus- 

 trates very well how this plant, in its chemical as well as bo- 

 tanical character, is related to the Hamatoxylon campechianum; 

 also, I found a substance like catechin in the Saraca. This 

 compound is found in the Acacias, to which class Saraca is 

 related by its chemical position as well as botanically. Saponin 

 is found in both of these plants as well as in many other plants 

 of the Leguminosae. The Leguminosae come under the mid- 

 dle plane or multiplicity of floral elements, and the presence 

 of saponin in these plants was to be expected. 



From many of the facts above stated, it may be inferred that 

 the chemical compounds of plants do not occur at random. 

 Each stage of growth and development has its own particular 

 chemistry. 



It is said that many of the constituents found in plants are 

 the result of destructive metabolism, and are of no further use 



1 Botanical Gazette, October, 1886. See ante, p. 168. 



2 Borodin, Pharm. Jour. Trans., xvi, 369. Pax. Firemy, Ann. Sci. Nat., 

 xiii. 



3 H. C. De S. Abbott, Proc. Acad.Nat. Sciences, Nov. 30, 1886. See ante, 

 p. 171. 



