Aspects of Ecology. 
247 
areas, so as to relieve the pressure on the colour tints. The whole 
subject has not yet passed beyond the experimental stage, and 
what we require is suggestion and trial in various fields rather than 
a universal scheme. 
The description of the making of medium-scale formation 
maps by means of the plane table and camera, using a commanding 
elevation as a base of observation, is of great interest to workers 
in hilly districts; and the determination of the general outlines of 
regions, provinces and vegetational zones, by recording the range of 
typical dominant genera on provincial and continental maps, is also 
of importance, particularly to continental ecologists. 
Several pages are given to the technique of photography from 
the stand-point of the ecologist, all the necessary operations being 
treated of consecutively. We have no space to criticise this treat¬ 
ment in detail, but it may be said that many useful hints are given, 
and while it is quite possible to obtain good vegetation photographs 
in other ways, the beginner will do very well to follow Dr. Clements’ 
instructions till he has acquired enough experience to put him in a 
position to vary his practice with advantage should he so desire. 
The section on Formation and Succession Herbaria is, we 
think, admirable. As “ basal material for developing the subject of 
comparative phytogeography” their importance is fundamental, and 
for educational purposes they are of unique value. Comparative 
ecological phytogeography based on such herbaria is, in our opinion, 
of far more value as a mental discipline than taxonomy based on 
ordinary floristic herbaria. 
Development and Structure of the Formation. 
Having in the sections just reviewed dealt with the methods of 
investigation and record of the formation, Dr. Clements now passes 
on to consider the facts of its Development and Structure. His 
view of vegetation as an organism is as legitimate as the familiar 
idea of a human society from the same point of view. Both con¬ 
ceptions are useful and desirable so long as it is remembered that 
they are essentially analogical, that these quasi-organisms do not 
possess many of the essential features of real organisms. The 
incomplete correspondence of organisms and quasi-organisms is 
illustrated by the statement that “ the functions of a formation are 
association, invasion and succession ” ; since none of these occur 
as functions or normal activities in a stable or adult vegetation, it 
would be truer to regard by them as processes or activities of the 
