Development of the Vegetation of New York State 29 
set free by the activity of forest fungi and especially of bac- 
teria becomes available energy for the further development 
of the community. 
Thus we are brought again to realize that vegetation de- 
velopment is an orderly thing; i. e., it is development in a 
real sense, determined by factors quite analogous to but per- 
haps more vaguely defined than those which determine the 
course of development of the adult plant from the seed or the 
embryo of the seed from the fertilized egg. Also the com- 
plex character of the climax forest society is further em- 
phasized in the contrast between those dominant members — 
trees — which contribute most to make the physical environ- 
ment of the forest and the fungi and bacteria at the opposite 
end of the scale, which by regulating forest floor sanitation, 
make the continuance of the community possible. 
LANDMARKS IN THE GEOLOGICAL HISTORY OF 
VEGETATION. 
We may now open the geological record with the apprecia- 
tion that the history of the evolution of the natural groups of 
the plant kingdom, the differentiation of growth forms in the 
vegetation and the problems of plant association were largely 
worked out at a period which seems very remote when meas- 
ured by the relatively brief period of human history. We 
may not here go into the record fully but merely measure 
progress by selecting again periods that will serve as land- 
marks. J have attempted to state briefly and with a view to 
their bearing on our present purpose what I understand to 
be a fair statement of the views of geologists and paleobotan- 
ists as embraced in the current teaching of these scientists. 
The Plant Life of the Coal Period. The Age of Ferns and 
their Allies. 
The Carboniferous period, as it used to be called, makes a 
good beginning point because it stands out more conspicu- 
ously by reason of its popular association with the origin of 
the world’s great coal supplies. If we regard coal as of veg- 
