116 
types of insects, scarcely at all with the ultimate effects of these 
operations. This point of view, however, colors the whole 
tone of the book, as one might expect from the exposition quoted 
above. It is not the effects upon the distribution of plants 
that it is aimed to present, so much as the individual response 
of the organs of plants to external environmental factors. It 
may be questioned by some, that in view of the distributional 
phase of ecology which has hitherto appropriated so much 
attention, it should not have received more notice from the 
author of the present work. That it has not indicates, at least, 
a significant trend in modern ecology. 
After a short chapter on germination in its relation to ecologi- 
cal problems, Professor Cowles takes up the much discussed 
and perhaps much overdone question of ‘Plant Associations." 
As an antidote for the association-idea run riot, to which we 
have unfortunately become accustomed, this chapter is the 
most effective imaginable. Coming as it does from an authori- 
tative American ecologist, it should serve to check those who 
have written as though the minute description of somewhat 
similarly constituted vegetation areas, was the end and aim of 
ecology. One very necessary concomitant of the study of 
plant associations, Dr. Cowles has probably intentionally 
omitted, perhaps because the book was intended for under- 
graduate use. But it seems doubtful if one can intelligently 
study the associations of plants, without taking into account 
the ancestral history of the species or genera under consideration. 
This, of course, involves larger problems of geographical dis- 
tribution, center and periphery of distributional frequency, 
climatic factors, and the geological history of the area treated. 
In bringing to a close this somewhat brief outline of this 
work, scholarly in its treatment, broad in its outline and com- 
- prehensive in its ideas as to the fundamentals of plant ecology, 
as the author has by his treatment conceived that science, it is 
a pleasure to record the fact that it will undoubtedly be a stand- 
ard book on the subject for years to come. А bibliography 
and an index complete the usefulness of the work for the student. 
I have found only a single error of fact, on page 495, where 
the wholly marine Zostera is stated to be a salt marsh plant. 
Trin abd > Se ror PPP 
occ or 
