Development of the Vegetation of New York State 165 
anced or equilibrium stage of our vegetation. According to 
this view, vegetation ceases to be the haphazard covering of 
the land with miscellaneous types of plants; it ceases to be 
the matter-of-course complement of our human welfare and 
becomes an orderly sequence of development somewhat in 
the same sense as the development of a single organism, as a 
tree for example, from the primitive stage of the fertilized 
egg to the fully differentiated body of the mature plant. If 
we should assume this to be an analogy then we should say 
of vegetation as of the developing tree that the general course 
of development has grown to be a fixed habit — the result of 
long environmental experience if you will— and that the 
daily or seasonal play of environment gets its response in the 
particular structure or habits of the organism or of vegeta- 
tion at any given stage of its development. But I do not 
wish to push any such analogy. I merely wish to show the 
force of the idea that vegetation development is a march of 
progress which involves the attainment of a highly advanced 
and relatively stable condition from primitive or pioneer be- 
ginnings. We have viewed this progress both in the large 
(theoretically) and in detail by the study of actual vegeta- 
tion stages. 
i. Review of Development in the Large. 
Geological records bear out these conclusions: 
(1) That before the Glacial epoch, the vegetation of North 
America was composed of essentially the same range of flor- 
istic elements (many species being identical with those of 
the present), of the same diversity of growth forms and the 
same general segregation into zonal relations — especially de- 
ciduous forest, conifer forest and arctic vegetation — as at 
present. 
(2) That the last great ice sheet must have obliterated 
vegetation from the northern half of the continent in eastern 
North America far enough southward to include practically 
the whole of New York State. 
