40 
C. E. Moss. 
insisted (p. 232) that a salt marsh characterized by suffru- 
ticose Salicornias “ must be set apart from ” salt marshes 
characterized by herbaceous Salicornias “ as a separate forma¬ 
tion,” merely because the plant form in the two cases is 
different. Such paradoxes occur throughout the whole of 
Warming’s book; and indeed this Janus-like “formation” is 
inevitable if plant form be allowed to enter into competition with 
habitat in the determination of formation. Warming’s view might 
find some justification if definite plant forms were invariably 
related to definite habitats ; but it is quite certain that this is not 
the case. For example, on salt marshes in the south of England, it 
is no unusual thing to find associations characterized (a) by herba¬ 
ceous species of Salicornia, (b) by suffruticose species (5. radiccins 
and S. lignosa), and (c) by a mixture of these. To place these 
associations in separate “ formations,” however, simply because of 
the different nature of the plant forms, is to reduce the study of 
formations to an absurdity. 
This criticism is not intended to convey the meaning that the 
study of plant form is not desirable or even essential. On the 
contrary, such a study in the hands of ecologists and plant geographers 
has led to most useful results. It must, however, be emphasized in 
Warming’s own words (1909: 5, 6) that “we are yet far distant” 
from the “ ecological interpretation of the various growth forms,” 
that “ it is an intricate task to arrange the growth forms of plants 
in a genetic system,” and that among growth forms “ it is difficult 
to discover guiding principles that are really natural.” 
It is to be regretted that Warming has made so unfortunate an 
experiment at a time when the delimitation of the formation by the 
habitat was becoming generally adopted ; and it seems clear that 
the Brussels Congress should not recommend a view of the plant 
formation that has not yet been shown to be capable of a logical or 
consistent application. Apart from Warming’s new book, a clear 
lead, however, was distinctly indicated; and, in my judgment, the 
Congress would be justified on the grounds both of historical 
and present-day usage, in ignoring tl^it element of Warming’s 
definition of the formation which refers to plant form, and in 
recommending for adoption the view that the formation should be 
determined primarily by habitat. If the Congress cannot under¬ 
take this step, it seems clear that the matter should for the present 
remain in abeyance. 
