Development of the Vegetation of New York State 47 
ZONAL RELATIONS OF NEW YORK FLORA. 
The presence of temperature zones about the earth has been 
vividly impressed upon the mind by many circumstances. It 
may have been first when you began the study of formal geog- 
raphy. The earth was found to be girdled by belts or zones 
from the equator to the poles. A high mountain in the 
tropics was shown to be similarly belted from a tropical base 
through temperate slopes to a frigid summit. Perhaps there 
were pictures showing these zones with their characteristic 
animals and plants or the peculiar costumes and occupations 
of the people. 
This zonal differentiation of the earth with respect to 
temperature and particularly the differentiation of life zones 
corresponding to and indeed visibly marking the temperature 
zones, is fundamental elementary teaching. The vital point 
for our present consideration is that all this represents a his- 
tory of environmental change and of adaptation of living 
organisms to the differentiated environments. We learned 
from the geological record that in the Carboniferous period 
for example, the climate of the earth was uniformly tropical, 
supporting a uniform, tropical vegetation even within the 
polar regions. Beginning, apparently, in the later Jurassic 
period, there ensued a gradual differentiation of climate 
marked by increasingly lower temperature toward the poles 
and notably by yearly fluctuations of temperature —1. e. 
alternating warm and cold seasons. Coincident with this 
there came about a segregation of species adjusted to differ- 
ent degrees along the temperature scale from tropical climate 
to arctic climate. What this means will be clear from a 
selection of well known or fairly well known species of plants 
from different latitudes along the north-south seale. Thus, 
mahogany, palmetto, giant magnolia, sweet gum, tulip-tree, 
chestnut, sugar maple, white pine, red spruce, balsam, paper 
birch, Bank’s pine, dwarf birch, arctic willows, tundra heaths 
and reindeer moss. 
We started out you remember, with the idea of emphasiz- 
ing the developmental aspects of vegetation. We especially 
