Floristik, Geographie, Systematik etc. 459 



Warming, E., Oecology of Plant s. Prepared for publi- 

 cation by M. Vahl, Percy Groom andj. Bayley Balfour. 

 (Oxford, Clarendon Press. 1909. 422 pp.price 8/6 net.) 



The original "Plantesamfund" published in 1895 was translated 

 into German in 1896 and 1902 with little alteration. The present 

 book is as Prof. Warming says "practically a new one", since it has 

 been revised throughout with the assistance of Dr. Vahl in Copen- 

 hagen and the English editors. As the original work is familiär to 

 most botanists, it will be sufficient to indicate the principal ehanges. 

 These consist of extensions which include most of the more recent 

 literature, and in the re-casting of portions in order to present the 

 facts more in unison with current opinion. The result is that this 

 most useful work has been greatly improved, and that many of the 

 original features which were rough and incomplete have disappeared. 

 The Introduction includes an important addition on growth-forms 

 (Lebensformen) in which there is a historical summary of the work 

 of recent authors (Drude, Krause, Pound and Clements, 

 Rankiaer, Warming), with a new Classification of the principal 

 growth-forms. Section I — Oecological Factors and their action — 

 has been brought up to date. Sect. II — the communal life of orga- 

 nisms — is only slightly altered, but the section (Kap. 6) on "Ver- 

 einsklassen" has been transferred to another place. The adaptations 

 of aquatic and terrestrial plants (Sect. III) is new; in it are brought 

 together the parts of the original work which dealt with morpholo- 

 gical and other features of water-plants and land-plants. The advan- 

 tages of this new arrangement are obvious, since a clear concept 

 of these adaptations is necessary, and in the original book the facts 

 were not well arranged for rapid reference. Following on this 

 (Chap. XXXIV) the author discusses oecological Classification, inclu- 

 ding the views of recent authors (Schimper, Clements, Gräb- 

 ner, etc.), but he maintains that "the most potent and decisive 

 factor is the amount of water in soil". This therefore becomes the 

 basis of a scheme of oecological Classification, which although ad- 

 mitted to be provisional is in some respects a distinct and noteworthy 

 advance; the original four groups — hydrophytes, xerophytes, halo- 

 phytes, mesophytes — are now extended into thirteen, as follows: 



A. Soil very wet, 



1. Hydrophytes (water-plants) 



2. Helophytes (marsh plants). 



B. Soil physiologically dry, 



3. Oxylophytes (on sour soil) 



4. Psychrophytes (on cold soil) 



5. Halophytes (on saline soil). 



C. Soil physically dry, climate of secondary importance, 



6. Lithophytes (on rocks) 



7. Psammophytes (on sand and gravel) 



8. Chersophytes (on waste land). 



D. Climate dry, soil-properties dominated by climate, 

 9. Eremophytes (desert and steppe) 



10. Psilophytes (savannah) 



11. Sclerophyllous formations (bush and forest). 



E. Soil physically or physiologically dry, 



12. Coniferous formations (forest). 



F. Soil and climate favour mesophilous formations, 



13. Mesophytes. 



A chapter (XXXV) is devoted to subdivions of the oecological 



