Development of the Vegetation of New York State 83 
the three northern continents would seem to le in the Terti- 
ary period. Speaking broadly, then was a time when the 
factors which stimulate plant response appear to have 
reached a degree of intensity, or of effective working together, 
sufficient to call forth what seems from the remote time of 
the present a marvelous bursting forth of plant energy, espe- 
cially in number of new species and diversity of growth 
forms. Among these factors must be reckoned favorable, 
diversified climate, the presence of new and favorable terrain 
and the combination of effective means of reproduction as 
represented in the, then, new type of plant —the angio- 
sperm — and particularly the floral structures of this group. 
It is certain that in the Miocene, for example, the climate 
was mild as far north as present arctic regions and that a 
heavy forest including many of our familiar genera — even 
apparently the same species in many cases — extended into 
the far north. Indeed, with forests on Greenland, Grinnell 
Land and Northern Alaska and with correspondingly mild 
climate in Europe and Asia this forest could extend, and evi- 
dently did extend, on into Europe and Asia.* Then could take 
place the free intermingling or migration of species between 
these continents which the present status of vegetation pre- 
supposes. Perhaps this close floristic relation is shown even 
more vividly than the present status shows it by certain 
species “* Miocene relicts ” in America but represented from 
Europe-Asia only by fossil forms (the species having mean- 
time become extinct there). Thus Taxodium distichum, at 
present in swamps of our southern states, was found fossil 
by Heer from Greenland to the McKenzie River and in 
Alaska and on the Island of Sachalin north of Japan.’ 
Numerous other species including one of Sequota (of which 
we have living Seguova gigantea (big trees) and S. semper- 
virens (red-wood). In the genera of this category were also 
Tiriodendron, Magnolia, Liquidambar, Sassafras and Nyssa. 
That is, all these now are represented by one or more species 
1Chamhbertin and Salisbury, loc. cit.. III, page 281. 
2 Harshberger, loc. cit., p. 174. Citations of papers by Heer, Engler, 
Gray and others will be found here and especially under the full bibliog- 
raphy, pp. 45-92. 
