404 BOTANICAL GAZETTE [MAY 
“sociological value of the species,’ and here perhaps lies the most valuable 
and suggestive portion of the French writer’s contribution. He asserts that 
the “sociological value” of species depends. upon their abundance, dominance, 
sorabnity, constancy, affiliation (fidélité), and genetic importance. When 
“abundance” and “dominance” are determined in a quantitative manner 
according to RAUNKIAER’s® methods, ‘“‘constancy” according to Du RIETZ, 
affiliation according to BRAUN-BLANQUET, and “genetic importance” accord- 
ing to PAVILLARD, the results will greatly clarify our concept of the association 
nd give a new importance to its floristic study. The “genetic coefficient’ 
expressing the relative importance of the species in the development of the 
association is perhaps the most important of these concepts and represents a 
decided contribution from PAVILLARD. 
ile there is practical agreement as to the importance of associations 
and little difference as to the use of the term, these two writers fail to agree 
when it comes to the consideration of units of a higher order. ANSLEY holds 
that the ‘‘formation” corresponds to habitat and cannot be satisfactorily 
characterized by life forms. He applies the term “formation” to a set of 
plant communities related developmentally and culminating in one or more 
associations. On the contrary, PAvitLarp regards life form as the only 
characteristic of a “‘formation,’’ which may thus be a community that is but 
a fragment of an association or one that contains several associations. He 
does not think that a satisfactory system of classification of plant associations 
is practicable in the present state of our knowledge. 
In attempting, in his admirable discussion, to harmonize the widely 
divergent opinions and the diverse attitudes of different ecologists, TANSLEY 
has been the first, perhaps, to appreciate fully the influence not only of differ- 
ence of training and of centers of interest but also of geographical situation. 
To himself it is not surprising that American ecologists, with their abundance 
of entirely natural areas, should belong to a school favoring a system based 
upon climatic climaxes and succession, or that those located in the middle 
west or northeast of the United States should appreciate the — of 
edaphic factors and distinguish their action from those of climatic 
similar consideration of the influence of geographical ae would 
probably have been useful to RoMELL? in explaining the segregation of Swiss 
and Scandinavian ecologists in the “inductionist” school, and the American 
ce English scientists in the “‘successionist” school. He shows, however, 
that some of the former, notably SERNANDER, have appreciated the dynamics 
of vegetation and employed many of the methods of the latter. His ‘plea for 
the use of hypotheses and of experimental methods is excellent, and the 
8 RAUNKIAER, C., Recherches statistiques sur les pasa oie Det. Kgl. 
Danske Videirksbernes Selskabe Biol. Meddeleser I, . 80. 
OMELL melee eh ne Physionomistique et batt sane Svensk Bot. 
eg 14: eit 19 
