Development of the Vegetation*of New York State 23 
that all these forms are bound together by ties of common 
descent. 
From these groups our State has derived its plant popula- 
tion or flora. See page 45. 
2. As To Growth Forms or the Working Units of Vegeta- 
tion and How They Work. 
Recalling our idea of vegetation development as the mass 
movement of plant life in taking possession of the land, and 
bearing in mind the concrete case cited where the glacially 
prepared terrain comprised in New York State was invaded 
by vegetation and the results arising from it, it is of course 
trite to remark that vegetation is a very complex organization 
— complex in somewhat the same sense as a people or a 
nation. To get closer to the details of vegetation work one 
must consider the working units, or as one may say, the 
growth forms. It is sufficient characterization of some of 
them to mention merely the group name as bacteria, fungus, 
moss, liverwort, to suggest the réle these play in vegetation 
work.! Yet of course there is differentiation of form and 
manner of living among these, so that with respect to fungi 
for example, there are those which play an indispensable role 
in the forest soil, in the disintegration of dead tree trunks as 
well as those which play a destructive part as parasites retard- 
ing the development of the whole vegetation community by 
disease. In the more highly differentiated plant groups, 
however, the group name — fern, club-moss, conifer — does 
not necessarily carry the idea of growth form (though to be 
sure in these special cases just cited the types in our vegeta- 
tion are in each group of much the same growth form) and 
vastly less so do the terms angiosperm, monocotyledon, di- 
cotyledon or even the family group name in most cases, butter- 
cup family, rose family, legume family, etc., suggest a special 
type of plant structure nearer than the broad name cormo- 
1 Assuming of course that the reader has some knowledge of the 
structure and life habits of such plants as bacteria (of decay, of fer- 
mentation, of disease), algae (water silk, water-felt, etc.) , fungi (mush- 
room bearing fungi, molds, rusts, smuts, ete.), lichens and so on. 
