28o Forestry Quarterly. 



succulent stemmed plants and woody plants with long-lived ligni- 

 fied stems). 



Having set forth as outlined above, the ground to be covered by 

 the volume, Warming proceeds to discuss in twenty-two chapters, 

 the factors of site, followed by seven chapters of remarkably clear 

 discussions of the adaptations to those factors. The larger por- 

 tion of the remaining chapters (lOO in all) describes the plant 

 formations of the earth. Warming's classification is based upon 

 both climate and soil as the following outline shows : 



A. Soil very wet; abundant water available, (i) Formations 

 in water; (2) formations in marsh. 



B. Soil physiologically dry ; water available only to a slight ex- 

 tent. (3) Formations on sour soil; sub-divided into low moors, 

 grass heaths, high moors, moss and lichen heaths (or tundra), 

 dwarf shrub heaths, and bushland or forest on acid soil. (4) For- 

 mations on cold soil, including chiefly the sub-glacial fell fields. 

 (5) Formations on saline soil, including salt swamps and deserts 

 and littoral swamp forest (Mangrove). 



C. Soil physically dry and its slight power of holding water de- 

 termines the vegetation. (6) Formations on rocks ; only herba- 

 ceous forms are given. (7) Formations on sand and gravel, in- 

 cluding dune heath, bushland and forest. (8) Formations on 

 waste land. 



D. Climate very dry and determines the character of the vegeta- 

 tion, the soil being of secondary import. (9) Formations of 

 deserts and steppes, including prairies. (10) Formations on 

 savannas, sub-divided into thorny savanna, true savanna and 

 savanna forest. (11) Sclerophyllous formations, sub-divided into 

 garique, maqui and sclerophyllous forest. 



E. Soil physically or physiologically dry. (12) Coniferous 

 forests. 



F. Soil and climate favorable to mesophyllous formations. 

 (13) Mesophytic formations, subdivided into arctic and alpinemat 

 grassland, meadow, pasture, masophytic bushland, deciduous 

 dicotylous forest and evergreen dicotylous forests. 



The four classes of plant formations of the previous Danish and 

 German editions of Warming's Oecology of Plants have been 

 extended to thirteen, resulting, as it seems to the reviewer, in a 

 greater clearness in conception and consequently in a more logical 

 grouping of plant habitats. A classification based upon both 



