Development of the Vegetation of New York State 21 
of peat and muck — should be placed the item of soil im- 
provement, first in the matter of aeration, drainage and con- 
stant moisture supply and second, because of the productive 
energy which had been added to the soil by this age-long ac- 
cumulation of the organic remains of forest life and the de- 
composition of them into simpler compounds capable of 
being absorbed by the living vegetation and of thus making 
the dead members contribute to the building up of new gen- 
erations of the living. 
A GENERAL REVIEW OF CLASSIFICATION, 
GROWTH FORMS AND PLANT ASSOCIATIONS. 
It will not be supposed because the end of the glacial 
epoch was taken as a landmark in measuring vegetation de- 
velopment that we should consider the vegetation story as 
opening with that chapter. On the contrary there is ample 
evidence to show that before the series of ice invasions of the 
northern continents set in, the earth’s vegetation had come 
to be essentially like that of the present. At any rate, the 
great groups of plants, algae and fungi, mosses and liver- 
worts, ferns, scouring rushes and club mosses, seed plants, 
including gymnosperms of the modern conifer types and 
angiosperms in great abundance and diversity were present, 
and there is reason to think that they were represented by 
essentially the same types of structure as at present — trees, 
shrubs, annuals, bulb and tuber bearing, grass and reed types 
and so on with the whole range of growth forms. No doubt 
the vegetation formed by these associated elements was es- 
sentially of present day aspect. 
But all these matters make it especially desirable for us 
to try to get back nearer to the beginning of the story of de- 
velopment of plant life and just at this point it is opportune 
to remind you of two or three items of current botanical doc- 
trine which it is well to have in mind while discussing in this 
brief summary the history of vegetation development. 
