REVIEWS 351 



be regarded as halophilous or psammophilous." The importance of the recognition 

 of physiological dryness co-existing with physical wetness is insisted on through- 

 out the book, as it was by Schimper. Hence peat-bog plants are no longer treated 

 under hydrophytes ; though, even in his earlier work, Warming stated quite fairly 

 the relations of the structure of what have been termed "bog xerophytes" to 

 their habitat. Warming, however, still retains his term " mesophytes," and 

 refuses to admit what many ecologists regard as indisputable, that Schimper's 

 term " tropophytes " {i.e. plants which are hygrophilous in summer and xerophilous 

 in winter) represents an advance on previous conceptions. Warming also re- 

 iterates his contention that the physical characters of the soil are more important 

 than the chemical. 



In Warming's present work, thirteen ecological classes are given. The classi- 

 fication of the major units of vegetation is undoubtedly less simple and clear 

 than the earlier one, and it is more than doubtful whether the loss in simplicity 

 and clearness is counterbalanced by any gain in accuracy. The attempt to 

 place every plant in a verbal class with the termination " -phyte " is probably 

 foredoomed to failure ; for, as Schimper has shown, many plants come in one such 

 class during one period of the year and in another such class during another 

 period ; and, as Warming himself has shown, certain plants possess some 

 structures characteristic of one such class and other structures characteristic of 

 another. Even in the present scheme, certain plants come in two of the classes. 

 The class Chersophytes is hopelessly unnatural, including such diverse plant 

 communities as Alpine " meadows," " Montenegrin expanses of poor grassland 

 occurring on stony ground," " alvar- vegetation " of Sweden, a peculiar type of 

 "waste herbage" in Madeira, and " bushland on dry soil," such as " Hippophaeta" 

 and "similar thorn bushland," Chodat's "garide," " palm bushland," and "fern- 

 heath," which is "likewise a kind of bushland and is produced by the widespread 

 bracken-fern"! "Coniferous formations," as an ecological class, cannot possibly 

 be admitted ; for it represents a confusion of the floristic and ecological points of 

 view, and a wholly unnecessary confession of the failure of the application of 

 certain definite ecological principles. The last class, "mesophytes," would appear 

 to be indefinable except in terms of itself. To the reviewer, it is clear that a 

 formal classification of the major units of vegetation on the lines attempted by 

 Warming and Yahl is either impossible or premature. In spite of this defective 

 classification, there is under each class a very valuable discussion on the nature 

 and requirements of various sub-classes, in addition to the more general treatment 

 of " growth-forms" (the " plant forms" of some authors) and of ecological factors 

 in the first three sections of the book. The book, like its predecessor, concludes 

 with a section on the struggle between plant-communities, in which the author 

 briefly states his opinions concerning the origin of species. 



The terminology used in this book with regard to the various plant-communities 

 is most unfortunate. For this terminology Warming probably cannot be held 

 wholly in fault. How many British botanists or even British ecologists could 

 state the significance of the following terms : " Elfin-scrub," " fell-field," " fell- 

 heath," "fern-heath," "grove-dell-formation," "high-moor," "low-moor," "orchard- 

 scrub," " sand-field," and " succulent steppe " (sic) ? Most of these terms can only 

 be regarded as quasi equivalents obtained by the simple process of literal trans- 

 lation. " Skill in interpretation and in apt expression " does not here force itself 

 obtrusively on the reader's mind. It may be fully acknowledged that this matter 

 of ecological nomenclature is a difficult one, particularly with regard to the 

 finding of good equivalents in different languages. It may, however, be suggested 



