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 Hcematoxylon 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 Hcematoxylon 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. Sei. Nat., 
xiii. 
3 H. C. De S. Abbott, Proc. Acad. Nat. Sciences, Nov. 30, 1886. See ante, 
p. 171. 
