HOOKS AND CURRE'NT LITERATURE 267 



Cycads, Dicotylodonous Woody Lianes, Grass-trees, Dicotyledonous 

 Stem-succulents, Perennial Grasses, Dicotyledonous Cushion Plants, 

 Geophilous Bulbous Plants, Saprophytes, Parasites, Amphibious 

 Plants, etc. Following this systematic presentation the author considers 

 it important to cUscuss the whole subject in a section devoted to ex- 

 planations and additions, where the preceding argument is clinched b}^ 

 descriptive matter treated under vegetative propagation, effective 

 distributional power of plants by means of seeds, and the exhibition 

 {Schaustelhmg) of flowers. 



The second section of the book treats of climatic influences, ])erio- 

 dicity and leaf characters. It deiils with the physiognomic effect and 

 organization of the leaf, as well as with matters of plant nutrition. Here 

 the author deals with the duration of the leaf, bud formation and protec- 

 tion, light and leaves, transpiration, etc. In the pages devoted to cli- 

 matic periodicity the author recognizes 18 climatic groups or climatic 

 geographic zones. This classification is intensely scientific and lends 

 itself to use in discussions of phytogeography amongst the botanic 

 elite, but for ordinary use in the class room and for other ordinary 

 purposes, the system is too cumbersome and the names are too long and 

 bulky for general acceptance. However, Drude has done ecologists 

 a service in drawing attention to the facts that he has presented in 

 this section of his work. The climatic groups are arranged under 

 four series with the prefi-xes iso-, tropo-, etesial-, and helio-. The 

 first has uniform annual light, temperature and rainfall, the second an 

 alternation of wet and dry seasons, the third a dry hot summer and 

 a winter with little light, while the fourth has a winter with little light, 

 effective in the production of a rest season. Phenology and other mat- 

 ters of climatic influence are presented in this section, together with 

 Professor Drude's views on the general phenomenon of periodicity in 

 relation to climate. He holds that periodicity is inherent to plants, 

 and that this inherent periodicity is the result of the exposure of plants 

 to millions of years of climatic periodicity. 



The third section is devoted to physiographic ecology. The ecolo- 

 gist must deal with the difficult problem of why species unite into cer- 

 tain communities and why they have the physiognomy which they pos- 

 sess. The author treats of the edaphic influences of soil, ground water, 

 bacteriologic soil content and the influence of lime and acids. The 

 work of G. Kraus published in 1911 (Boden and Klima auf kleinstem 

 Raum) is mentioned specifically. He quotes Jaccard's law on the dis- 

 tribution of species in alpine meadows and pastures and deals with the 



