1921] CURRENT LITERATURE 403 
NOTES FOR STUDENTS 
Ecological concepts and nomenclature.—All recent discussions of the 
classification of vegetation make it evident that ecologists are far from agree- 
ment upon any one system. The been ows and confusion are 
deplored by both Tansteys and PAvitta The latter gives further 
emphasis to his former statement nen the species and the association con- 
stitute the two fundamental unities of ecology or geobotany, and his two main 
divisions of the subject are based on these unities. As each of these units 
may be considered from the floristic, the genetic, and the ecological viewpoint, 
there results six subdivisions of the science. Conside ering the desirable impli- 
cations of the term “phytosociology”’ when used to designate the study of plant 
communities, and translating PAvILLARD’s terms freely, the six subdivisions 
of ecology may be designated: (1) floristic geobotany, (2) genetic geobotany, 
(3) ecologic geobotany, (4) floristic phytosociology, ( > genetic phytosociology, 
and (6) ecologic phytosociology. The first three are devoted to the consideration 
investigation of vegetation. With this TANSLEY seems in agreement, and 
further holds that such a unit of vegetation should desis and usefully be 
regarded as an organic unity or quasi-organism. ANSLEY, however, would 
limit the application of the term “association” to mature units in relatively 
stable equilibrium with their environment. These are the climax associations 
or permanent associations of other ecologists. To transitory or developmental 
associations he would apply CLEMENTS’ term of “associes 
Being in agreement that the association is the fosilaneatal unit of phyto- 
sociology, TANSLEY and PavILLARD emphasize the importance of the study 
of its development, the former clearly recognizing the principal of “succes- 
sion” and the existence of both climatic and physiographic (edaphic) climaxes, 
and the latter devoting one of his subdivisions of the science (“genetic phyto- 
sociology”) to problems of the development of associations, although he 
points out that such studies are not often undertaken or appreciated in con- 
tinental Europe. TANSLEY insists upon the study of the morphology of asso- 
Ciations, that they are essentially topographical units, and are in the first 
instance to be determined empirically, while Pavittarp regards floristic 
composition as their most essential characteristic. This floristic composition 
includes not only accurate lists of the species, but also consideration of the 
ANSLEY, A. G., The classification of vegetation and the concept of develop- 
ment. Jour, Ecol, 8: kin: 1920. 
6 PavILL arn, J., Espéces et associations; essai phytosociologique. Montpellier. 
PP. 34. Oct. 1920. 
7 Bor. Gaz. 70:183-185. 1920. 
