49 
Fundamental Units of Vegetation. 
of ecology and plant geography indicated in this paper. The mono¬ 
graphers of the wider areas have still to concentrate attention on a 
natural grouping of formations, the investigators of the very re¬ 
stricted areas on the factors of the habitat and on the responses 
made by the vegetation to these factors. Formations themselves 
require to be carefully delimited ; and the associations of each 
formation need detailed study from the points of view of zonation, 
alternation, succession, and floristic composition. The study of 
vegetation touches on physiology at many points, hut at present there 
is not and cannot be any essential identity between them: it needs 
the systematise hut it is in no sense a branch of taxonomy. 
Vegetation must be studied from the standpoints of its develop¬ 
ment, its structure, and its activities; and the object of this study 
is the elucidation of the relationships of vegetation to the factors 
of the habitat. 
LITERATURE REFERRED TO. 
Beck von M., G., 1901. “ Die Vegetationsverhiiltnisse der illyrischen Lander” ; 
in Engler u. Drude, Veg. d. Erde, IV; Leipzig. 
„ 1902. “ Uber die Umgrenzung der Pflanzenformationen ” ; 
in Osterr. Bot. Zeitsclir., LII. 
Blackman, F. F., and Tansley, A. G., 1905. “Ecology in its Physiological 
and Phytogeographical Aspects”; in New Phytologist, 
IV. (Review of Clements’ “ Research Methods in 
Ecology.”) 
Bonpland, A., 1S07. See Humboldt and Bonpland. 
Brockmann-Jerosch, H., 1907. “ Die Flora des Puschlav (Bezirk Bernina, 
Kanton Graubiinden) und ihre Pflanzengesell- 
schaften ” ; Leipzig. 
Brown, F. B. H., 1905. “A Botanical Survey of the Huron River Valley, III: 
The Plant Societies of the Bayon at Ypsilanti ” ; in 
Bot. Gaz., XL. 
Cajander, A. K., 1903. “ Beitriige zur Kenntniss der Vegetation der Alluvionen 
desnordlichen Eurasiens. Die Alluvionen desunteren, 
Lena-Thales ” ; in Act. Soc. Sc. Fettn., XXXII. 
Celakovsky, L., 1869-1874. “ Prodromus der Flora von Bohmen ” ; Prag. (Cited 
in Loew, 1879). 
Clements, F. E., 1898; 1900. See Pound and Clements. 
„ 3902. “ A System of Nomenclature for Phytogeography”; 
in Engler’s Bot. Jahrb., XXXI., Beibl., 70. 
„ 1904. “The Development and Structure of Vegetation”; 
Lincoln, Neb., U.S.A. 
„ 1905. “Research Methods in Ecology”; Lincoln, Neb., 
U.S.A. 
Cowles, H. C., 1899. “The Ecological Relations of the Vegetation on the 
Sand Dunes of Lake Michigan”; i n.Botan. Gaz., 
XXVII. 
1901. “ The Physiographic Ecology of Chicago and vicinity: 
a Study of the Origin, Development, and Classification 
of Plant Societies ” ; in Botan. Gaz., XXXI. 
