SemekeENT LITERATURE 
BOOK REVIEWS. 
Methods of ecological investigation. 
ONE OF THE most important recent contributions to the literature of ecology 
is a work on the development and structure of vegetation, from the hand of 
Dr. CLements.* The object of this and a forthcoming volume is to present 
in a systematic and detailed manner the methods of ecological research that 
have been employed by the author for .a number of years in the prairies and 
Woodlands of Nebraska, and in the mountains of. Colorado. The principles 
enunciated here were formulated as working hypotheses in 1898, and have since 
been submitted to rigorous field tests. The present paper deals in particular 
with the biological side of vegetation, while the forthcoming work is to be concerned 
more with the physical aspects. 
The fundamental phenomena of vegetation are regarded as invasion and suc- 
“ssion (dynamic), zonation and alternation (static), and association, the latter 
“presenting the stage to which vegetation has been brought. A section is devoted 
to each of these topics, and in each case there is given a historical survey of the 
phenomenon, followed by a keen analysis, and a bibliography. One may classify 
*soclations with relation to stratum, light, water, etc., but of these CLEMENTS 
ongly emphasizes the dominance of the water factor. He inclines not to accept 
ScHIMPER’s edaphic an 
pe tons are both climatic and e aphic. Invasion consists of the movement 
cy and establishment (ecesis) of species. In discussing this topic, a 
T of t 
“rms are introduced applying to the plant member that migrates, the 
of the contrivance which facilitates migration, and the agent involved. 
olygenesis (theory of po 
accepts j 
. enn (on denuded soil). Some excellent terms are introduced, indicat- 
tl sad ¢ me of movement in the succession, xerotropic, mesotropic, and hydro- 
The ¥ application is obvious. 
cute, a ives laws of succession, which will be admitted at once in most 
ugh it is likely that some may require modification. Zonation has been 
iy alternation 
slightly except b 
rn 
wey of N mf E.. The development and structure of vegetation. Botanical 
at eb: ee 
2. 1904, mia Studies in the Vegetation of the State, III. 8vo. pp- 175- 
1904) 
326 
