﻿294 BOTANICAL GAZETTE [april 



The most interesting of the chapters is the one which presents the 

 dynamics of the heath formation. Graebner combats with great vigor the 

 rather common view that heaths represent areas once forested, in which refor- 

 estation has been prevented directly or indirectly through the agency of man. 

 He argues that most heath areas show no tendency to return to forests, when left 

 quite free to do so, and that in many cases heaths even encroach upon forests. 

 As already noted, the chemical nature of the soil is believed to be inimical to 

 tree growth, and the Oristeiii of the heath subsoil adds to the difficulty. The 

 author departs from most commonly accepted views in regarding the climate 

 as fundamentally responsible for the condition of these heathy soils. The 

 most usual origin of the heath is from forests in which the soil has been made 

 gradually poorer in necessary salts, partly by the trees themselves but more 

 especially by leaching. The latter process is thought to be greater in north- 

 western than in northeastern Germany, because of greater rainfall. Hence 

 the heath prevails westward under original soil conditions that bring forth 

 forests eastward. The heath may originate on naked sand through a series 

 of stages, the first of which is characterized largely by algae and moss 

 protonemata. Graebner also shows how heath moors may originate, giving 

 three cases: development from water, from naked soil, and from forests. 

 The heath may develop from these moors, if for any reason they become dry. 

 Sections are devoted to the soil species and climatic features of the heath 

 region. 



The second part of the book treats of the various types of heaths, which 

 the author divides into four groups, (i) Heaths proper, including Calluna, 

 Tetralix, Empetrum, and Sarothamnus heaths ; (2) grass heaths, dominated by 

 xerophytic grasses; (3) forest heaths, mostly dominated by pines; (4) Wein- 

 gaertneria heaths. The final section deals with the relation of the heath to 

 other formations. This volume is easily the most readable of those which have 

 been thus far published, and it is to be hoped that other volumes which deal 

 with definite formations will follow soon, — H. C. Cowles. 



Vegetation pictures. 



Karsten and Schenck^ have inaugurated a valuable series of illustra- 

 tions of the world's vegetation, of which two numbers have thus far 

 appeared. Each number contains six excellent heliotypes, representing 

 characteristic plant formations in various parts of the world. Full descrip- 

 tive text accompanies each picture, so that reference to various original 

 monographs is scarcely necessary. The first number, prepared by Schenck, 

 deals with southern Brazil, presenting views of the tropical rainy forest, 

 myrmecophilous trees, palms, epiphytes, and Araucaria woods. Karsten has 

 given out the second number, which contains views from the Malay archi- 

 pelago, presenting the Nipa formation, tree ferns, rainy forest and street 



3KARSTEN, G.. and Schenck, H., Vegetationsbilder. 4to. Jena; Gustav Fischer. 

 1903. Subskriptionspreis iedes Heft von 6 Tafeln M 2,^0. Einzelne Hefte M 4- 



