410 Dawson— Bearing of Devonian Botany on 
Art. LIL—On the bearing of Devonian Botany on Questions 
as to the Origin and Katinction of Species ; by Dr. J. W. 
Dawson. 
[The theoretical views contained in this section, though necessary to give 
completeness to the subject, are not suitable for an official report, and are, there- 
fore, printed separately by the author, for circulation to those who may be inter- 
ested in them as matters of science. ] 
Fossru plants are almost proverbially uncertain with refer- 
ence to their accurate determination, and have been regarded 
as of comparatively little utility in the decision of general ques- 
tions of paleontology. This results principally from the : 
mentary condition in which they have been studied, and from 
the fact that fragments of animal structures are more definite 
and instructive than corresponding portions of plants. 
that, with reference to such points, the evidence of fossil plants, 
when properly studied, is, from the close relation of plants to 
ose stations and climates, even more valuable than that of 
animal fossils, ss 
It is necessary, however, that in pursuing such SON 2 
nen c forms, whether with reference to a single 
geological period, or to successive periods; and ced 
¢ for stating here some general principles, whic b 
rtant for our guidance, with reference to the 
oA eas floras which form the subject of this memoir. 
(1.) ists proceed on the assumption, vindicated by e* 
ical purposes, the same assumption with “ag 
