“ The Oecology of Plants.” 
2 19 
Europe and America, and the publication of Schimper’s “ Pflanzen- 
geographie auf physiologischer Grundlage ” in 1898 and of Professor 
Clements’ “ Research Methods in Ecology ” in 1905 have marked 
great strides in that development. The subject is no doubt, as 
Professor Warming remarks (Preface, p. vi.) still in its infancy, but 
it is at least out of its swaddling clothes. And the task of writing a 
general text book of ecology which shall be both comprehensive 
and atthe same time clear and consistent in treatment, has become, 
if not, indeed, impossible, at least far from easy. The scope of 
plant-ecology is enormous, and while particular observations have 
multiplied with great rapidity, the development of correlating 
principles has hardly kept pace. The subject, as Clements has 
pointed out, has developed very unequally. There has been much 
cultivation of the surface phenomena, and too little penetration to 
deeper levels. Into the causes of this we need not enter here, but 
the fact has a considerable bearing on the present work. The great 
feature of the “ CEcologische Pflanzengeographie ” was the consistent 
treatment of plant-communities in relation to the water of the 
environment, as seen in their primary classification into mesophytes, 
xerophytes and hydrophytes, with halophytes standing apart, though 
closely allied to the xerophytes. This classification was a particularly 
happy one for the purpose of developing the subject fifteen years 
ago, but it was of course provisional, and in the present work has 
given place to a much greater number of classes, in which the old 
simple relation to water is largely lost. At the same time the 
inclusion of very numerous descriptions of and allusions to local 
plant-communities in different parts of the world, about most of 
which we know very little, has led to a considerable loss in the 
quality of unity of treatment and “ Uebersichtlichkeit ” which were 
such conspicuous features of the original work. These drawbacks 
were no doubt inevitable in view of the development of the subject 
we have noted, unless indeed a new principle or principles of 
treatment could have been found. We already have a finely 
illustrated and comprehensive treatment of the vegetation of the 
world in Schimper’s “ Plant Geography,” and it is perhaps doubtful 
if anything on similar lines will serve, at present, any very useful 
educational purpose, though as a book of reference for the professed 
student of ecology the present work, with its abundant citation of 
the most recent investigations, must be of considerable value. 
The general plan remains the same as in the earlier work. 
Following upon the Introduction, which is much longer, and contains 
a treatment of “ growth-forms,” there is a section devoted to the 
discussion of ecological factors and their action, and then one on 
the communal life of organisms and on plant-communities. A new 
section follows, on the adaptations of aquatic and terrestrial plants, 
and on ecological classification ; and then the plant formations are 
treated under thirteen classes instead of the original four. Finally, 
as in the earlier work, there is a section on the struggle between 
plant-communities. The list of literature extends to thirty-two 
pages and contains considerably over a thousand titles, including 
many works which are not referred to in the text. 
The more extended treatment of growth-forms in the Introduction 
is welcome. A short history of the attempts to classify these is 
given, culminating with the author’s own discussion published last 
