Fundamental Units of Vegetation. 31 
(p. 29) dissatisfaction with Grisebach’s physiognomical definition of 
the formation, and held that whilst this might serve to distinguish 
classes of formations, a precise idea of the formation can only be 
obtained by taking into account the floristic composition. As there 
is a definite relation between habitat and the total floristic compo¬ 
sition, this aspect of the formation may be regarded as in accordance 
with much of the later work of ecological plant geographers. Drude 
applied his general ideas to the vegetation of the Hercynian hill- 
country of Central Europe, which he subdivided into twenty-seven 
formations. These he then subdivided into associations; for example, 
the halophyte formation (p. 48) he subdivided into “ Salzsumpf- 
Bestand,” “ Salztrift-Bestand,” and “Trockne Salsolaceen- Flur.” 
In connection with the descriptions of British moorland associations, 
the “ montane Grassmoor-Formation (Warming) ” is especially 
interesting. This formation (p. 44) Drude subdivided into the 
following associations:—“ Sumpfwiesen-Bestand,” “ Binsenmoor- 
Bestand,” “ Wollgras- und Riedmoor-Bestand (“ Griinmoore ”),” 
and “ Torfsumpf-Bestand ” ; and the first three of these appear to 
be very closely related to some of the associations which occur on 
British upland peat moors. Although Drude at the outset of this 
communication stated that his object was the deepening of floristic 
studies, he by no means overlooked the importance of the habitat. 
He laid down (p. 28) the general principles that formations should 
be based on all conditions of existence (soil, water, atmospheric 
moisture) and on the associated species, and that the alternation of 
various principal and subordinate species within the same formation 
gives rise to the various associations (Bestande). 
Warming (1895: 3-10) was so impressed with the confusion 
which had overtaken the term “ formation ” that he recommended 
its disuse. The wider meaning Warming thought might be indicated 
by the word vegetation ; and for a plant-community of no assigned 
rank he used the term Plantesamfund (Pflanzenverein). The term 
“ formation,” however, had become so firmly rooted in ecological 
and phytogeographical literature that even the weight of Warming’s 
authority was insufficient to cause its extirpation ; and the trenchant 
treatment of the “ formation ” by Drude in the following year 
(coincident with the appearance of Knoblauch’s German translation 
of the Plantesamfund) gave the term a new lease of vitality. 
In his Deutschlands PJlanzengeographie (1896), Drude again 
emphasized the habitat, and stated (p. 281) that the plant-covering 
of a country is expressed in the arrangement according to definite 
