CURRENT LITERATURE. 



Ecology of Plants. By Eug. Warming. Assisted by Martin 

 Vahl. Prepared for publication in English by Percy Groom and 

 Isaac Bayley Balfour. Oxford, Clarendon Press. 1909. 



The scope of ecological inquiry is so well defined by Warming 

 that it seems worth while to quote it here: "To find out which 

 species are commonly associated together upon similar habitats; 

 to sketch the physiognomy of vegetation and the landscape; to 

 answer the questions : why each species has its special habit and 

 habitat, why the species congregate to form definite communities, 

 why these have a characteristic physiognomy." The last questions 

 are the really difficult tasks of ecology and their solution leads to 

 the investigation of the problems concerning the economy of 

 plants, the demands they make upon their environment, and the 

 means that they employ to utilize the surrounding conditions and 

 to adapt their external and internal structure and general form for 

 that purpose. 



The result of such activities on the part of the plant is the 

 growth form, or in other words, the growth form is the expres- 

 sion of the degree of the external and internal adaptation of a 

 plant to the natural conditions in which it lives. On this basis the 

 author makes six classes of growth forms, as follows : Hetero- 

 trophic, parasites and saprophytes evidently derived from self- 

 sustaining plants; aquatic; muscoid; lichenoid (mosses and 

 lichens being separated by their method of nutrition), and, sixth, 

 all other self-sustaining plants. The latter class is divided into 

 annuals and perennials. The subdivision of the perennials is 

 based upon such points as the duration of the vegetative shoot, the 

 length and direction of the internodes, the position and structure 

 of the renewal buds, the duration of the leaves, the adaptation of 

 the nutritive shoot to the conditions of transpiration and the 

 capacity for social life. Following these lines, the author groups 

 the perennials into four sub-classes, renascent herbs, rosette plants, 

 creeping plants and plants with erect long-lived shoots (sub- 

 divided into cushion plants, undershrubs, soft stemmed plants, 



