6 BOTANICAL GAZETTE [SEPTEMBER 
seem to meet with general approval in this country at least. In 
this case there is the additional objection that the more familiar 
and convenient term is restricted in use to a minority of cases. 
3. That the double aspect, abstract and concrete, approved for 
the association be recognized also for the formation. The abstract 
concept of the formation, indicated by the use of the definite article, 
would thus correspond with the Brussels Congress description, and 
would constitute the formation abstract as a sort of ecological 
species. The formation concrete might then be regarded simply 
as any association complex, characterized by a dominant association 
but including all adjacent associations, whether mature or imma- 
ture, and other more or less anomalous or unidentified communities 
connected with them. Thus the formation concrete in general 
would correspond to NicHots’ physiographic formation, although 
the habitat is omitted from the definition, and contiguity made 
the basis on which the communities are united in the formation. 
Individual formations may be named either from the dominant 
association or from the physiographic nature of the area occupied. 
4. If a unit above the formation is desired, it will be found con- 
venient to associate the formations of a region in a larger group, 
which NicHots (6), following Scutmper, has characterized as a 
climatic formation. TANSLEY has demonstrated the inadvisability 
of the term, but the fact remains that the concept is a convenient 
one, especially for field use, and the writer suggests that the term 
“formation complex,”’ or simply “complex,” be used for this con- 
cept. If it be objected that complex is equally applicable to lower 
grades of units, and is actually in use with them, a special term, 
such as ‘“‘aggregate,”’ might be employed. It does not seem advis- 
able to use the term formation, even if qui ied by a descriptive 
adjective, for two classes of units of different grade. Indeed this 
concept may be identified sufficiently by general expressions already 
in use, such as vegetation, formations, or even forest (as in ‘‘ vege- 
tation of Connecticut,” “‘formations of the Great Lakes region,”’ 
“temperate deciduous forest,” etc.). 
On the whole, it seems advisable to follow TaNsLey and NICHOLS 
in emphasizing the vegetational content of the community and 
regarding the habitat as the sum total of the environmental factors, 
