HIGHER AND LOWER PLANTS 259 
our well-established scientific facts would still be buried from 
sight. 
The chemical analysis of the dead plant and the study ol 
the chemical changes occurring in the living plant are among 
our means for some of these investigations; and much of all 
the knowledge derived from each field of chemical research 
may be utilized in aiding to unravel the mystery of these changes 
in the vegetable cell. 
In the mineral kingdom certain elements are invariably 
associated with others, as nickel with cobalt; and in plants 
not only do we find two or more compounds invariably present 
together, — i. e., tannin and starch in the tannin groups, lime 
and saponin in the pink family (CavyophyllacecR) / resins and 
saponin in all of the saponin-containing groups, and sugar 
and silica in the grasses ( Graminea ), — but also in certain 
plant groups we notice the predominance of special com¬ 
pounds, and their absence in other groups. The grouping of 
these compounds in definite association must bear some re¬ 
lation to their respective sequence and formation, and cannot 
be the result of accident. That the cinchona plant does not 
manufacture the alkaloids of the poppy, but each its own 
particular series of compounds, illustrates this. 
I have said, elsewhere, 1 2 “The chemical compounds of plants 
do not occur at random. Each stage of growth and develop¬ 
ment has its own particular chemistry. . . . The result of 
experiment shows that the presence of certain compounds is 
essential to the vigor and development of all plants, and par¬ 
ticular compounds to the development of certain plants.” 
It may be inferred that “plant chemistry and morphology 
are related. Future investigation will demonstrate this re¬ 
lation.” 
The theory of evolution, which underlies all mineral and 
organic forms, comprises the evolution of the component parts 
of the whole, and since the structural bases of minerals and 
plants are chemical compounds, their evolution must neces- 
1 Die Pflanzenstofe, by Hilger and Husemann, p. 542; E. v. Wolff, J. -pr 
Chem., li, 24; lii, 86; Wolff, Aschenanalysen, 1881, pp. 144, 145. 
2 “The Chemical Basis of Plant Forms,” p. 232, ante. 
