nditions which control the synthesis and gradual formation 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[47] read in Buffalo at the last meeting of the American
Association for the Advancement of Science, various 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.[48]

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 important dyes,
e.g., indigo, logwood, catechin. The former is obtained principally
from different species of the genus _Indigofera_, and logwood from the
_Haematoxylon_ and _Saraca indica_.

The discovery[49] of haematoxylin in the _Saraca indica_ illustrates
very well how this plant in its chemical, as well as botanical,
character is related to the _Haematoxylon 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 middle 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 in the
plant's economy. This subject is by no means settled, and even should
we be forced to accept that ground, it is a significant fact that
certain cells, tissues, or organs peculiar to a plant secrete or
excrete chemical compounds peculiar to them, which are to be found in
one family, or in species closely allied to it.

It is a fact that the chemical compounds are there, no matter why or
whence they came. They will serve our purposes of study and
classif