HIGHER AND LOWER PLANTS 279 
tend to be what they are not. When will all of these intricacies 
of nature’s secrets belong to commonplace facts ? The day is 
distant. And in the meantime my hour is drawing to a close; 
and, to return to my first statement of the evolution of the chem¬ 
ical elements, I would say that the studies 1 of Lecoq de Bois- 
baudron, Auer, Demarjay, and Crookes on didymium, and the 
latter’s researches on yttria, and more recently on the crimson 
line of phosphorescent alumina, 2 go to show that the mole¬ 
cules of these so-called elements are compound, and if I have 
dwelt at all upon this subject, in connection with plant life, it 
is on account of the indisputably serious nature of the inves¬ 
tigations in this field. The following concluding remarks of 
Professor Crookes’s address 3 show that the theory of the 
chemical evolution of plant compounds has an able ally. He 
says, “We cannot venture to assert positively that our so-called 
elements have been evolved from one primordial matter, but we 
may contend that the balance of evidence . . . fairly weighs 
in favor of this speculation. . . . The doctrine of evolution, as 
you well know, has thrown a new light upon and given a new 
impulse to every department of biology, leading us, may we 
not hope, to anticipate a corresponding wakening light in the 
domain of chemistry. I would ask investigators not neces¬ 
sarily either to accept or reject the hypothesis of chemical 
evolution, but to treat it as a provisional hypothesis; to keep 
it in view in their researches, to inquire how far it lends 
itself to the interpretation of the phenomena observed, and to 
test experimentally every line of thought which points in this 
direction.” 
From the above sketch I have attempted to show that the 
hypothesis of evolution may also apply to the chemistry of plant 
compounds, and that plant chemistry will be found, like any 
special study, to include many others. It is, however, excep¬ 
tional in its broad range, and the variety of its topics, like the 
variations of flower-species, may be cultivated to suit the taste 
of the investigator. 
1 Comp. Rend., t. civ, 1887, p. 165, M. Henri Besquerel. 
2 Chem. News , Jan. 21, 1887. 
3 Delivered before the British A. A. S., 1886. 
