252 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



which is fully illustrated, mostly by line-drawings. One other little 

 point we notice that the fern enthusiast will be sure to take exception 

 to — the statement that many varieties are not constant. This is 

 true if forms induced by the immediate surroundings of the wild plant 

 are called varieties, but not of many others. 



" Vegetation of the Peak District." By C. E. Moss. 8vo., 235 pp. 

 (University Press, Cambridge, 1913.) 12s. net. 



This is a valuable work of its kind, being a full description of the 

 " Associations " of plants of the country. It commences with a 

 general description of the Peak and its climatic conditions, the remain- 

 ing eight chapters dealing with the Woodland, Scrub, Grassland 

 Associations, those of rocks and screes, marsh and water, moorland 

 and cultivated areas. There are thirty-six excellent photographs 

 and two coloured maps. 



The book affords a good illustration of the primary part of modern 

 1 1 Botanical Geography . ' ' No student is to-day satisfied with collectin g 

 plants, quite irrespective of any interest in their natural surroundings. 

 Plant " Ecology," or the study of plants at home, implies observations 

 of every kind which constitute the " environment " of the individual 

 plant to be studied. As the latter is usually associated with others, 

 the " group " is to be studied to find out how it is they live together. 

 This leads to the study of the inorganic " factors," light, shade, 

 degree of water, soil, &c. 



Then follows a careful internal anatomical study to discover how 

 or why this is correlated with the external factors or conditions of life. 



M. Aug. Pyramus de Candolle appears to have been the pioneer 

 in Ecology, in his article on " Botanical Geography " (" Dictionnaire 

 des Sciences naturelles," vol. 18, 1820). He takes each factor, heat, 

 light, water, soil, atmosphere &c, and tabulates the details of plant- 

 structure under each ; and thus recognizes " stations " e.g. salt 

 marshes; fresh and stagnant water, &c. He recognizes the universal 

 struggle for existence, and how " the fittest " under the circumstances 

 survive. Thus " Car ex arenaria in sand chokes those which in clay 

 choke it." In fact his article might have been the model for Schimper's 

 " Plant Geography," for he too recognizes much more than the 

 " grouping of plants into separate floral districts. . . The essential 

 aim of geographical botany will be an inquiry into the causes of 

 differences existing among the various floras. . . Experience shows . . 

 that differentiations [of structure] are profoundly and rapidly modified 

 by changes in the environment, every one of which immediately 

 involves a change in the organization of the plants." This was 

 Darwin's alternative explanation of evolution, which is now widely 

 accepted by botanists as superseding his tentative theory of the Origin 

 of Species by means of Natural Selection. 



This side of Ecology, however, is practically untouched by Mr. 

 Moss, who, nevertheless, has done excellent work in the primary 

 department of Ecology. 



