NATURAL SELECTION AND PLANT EVOLUTION 181 
so far, i aac fossil ng is unable to dogmatize as to how 
this or that species has bee ved. 
ane more as ies the complete life- ram! of a 
number of closely related species of fossil plants, may, like 
our far better-informed brother zoologists, amily to erat how 
Natural Selection has Ww ee zal Fo r the present we t have 
t we m 
better to speak of Natural Bélastion: fiat as an agent bu tas the 
result (correlated with physical selection of oe: with at es 
changes it consists) of the struggle for existen 
Indeed, Evolution itself is, rightly considered only the out- 
come of the adjustment of the organism t environment * 
5 anmlogeilll & "pink of the eee of Peake” man— 
differentiate, for sake of comparison, between genetic aed mental 
or psychic processes; the Siok” thatly Sana included in the 
former in any ideal philosophy, which must ever the mentor 
wa intermediary, , 
at least not a ity causa, as some would have it) by these adapta- 
useful adaptations—it i indeed we are warranted in drawing any 
such distinction—we may, -anpteemreent apes tentatively then of 
the work of ecleotion: whether tural or physical. In 
reality, in many of the cases in bid aly Sivan selection can 
The action of organism upon organism is, however, abun- 
dantly exhibited, in the Carboniferous Period, in the mode of 
deposition of the plants comprising the flora at that time. For 
we find at many horizons, where deposition 7m situ m. ay well be 
argued to have taken place for long —— without abaastlo that 
there is a predominance of certain types of an arborescent char- 
acter. By the mere Me ee extent of growth there is a 
restriction in the dist _ of not only — and genera, but 
whole orders. Thus we find the well-known revailing 
almost to the peslaatod st others, which linger a into entirely 
different conditions. The humid but warm climate was entirely 
unsuited to Walchia or Voltzia, which persist into post-Carbo- 
ha 
* The exi ee divergent, or of retrogressive, forms 
bears = ara whilst t of progressive — testifies to eter 
conus of sole rcesiige and the natural progress of perfection from rom eine to 
