CURRENT LITERATURE 



BOOK REVIEWS 



The vegetation of Lake Constance 



An admirable illustration of the intensive study inspired in his students 

 by Schroter is found in the elaborate and thorough monograph on the vege- 

 tation of the Untersee by Baumann. 1 The Untersee is one of the lower arms 

 of Lake Constance on the border of Germany and Switzerland, it being through 

 this arm that the Rhine leaves the lake. After an account of the geology, 

 geography, and hydrography, Baumann gives a most interesting account of 

 the different sorts of calcareous deposits, which here take an unusually impor- 

 tant part in soil formation, as noted years ago by Honsell. Calcareous tuffs 

 are formed in extensive amount through the agency of algae. These organ- 

 isms withdraw carbon dioxide from the calcium bicarbonate in the waters, and 

 the remaining calcium monocarbonate is deposited about the algae as a crust. 

 Later the plants die, leaving only the incrusting masses. In time these pro- 

 cesses result in the formation of extensive banks, of which the inner layers are 

 dead, whereas the outer layers contain living algae; these banks, therefore, 

 are precisely comparable to coral reefs. At times the calcareous deposits are 

 in grains, each grain representing the stratified calcareous accumulations about 

 an alga. The Island of Langerain has been formed mostly in this manner. It 

 is thought that these calcareous deposits have been accumulating continuously 

 since the ice age, and they are still accumulating. 



The great body of the work is devoted to a detailed study of the species 

 ecology of the characteristic plants. This represents a vast amount of valu- 

 able work, which will be of first importance to all students of the vegetation 

 of lakes and swamps. A chapter is devoted to the plant associations, which 

 are of the usual sort for such habitats. Only the larger plants are discussed 

 here, the plankton and the profundal benthos being omitted. The associa- 

 tions are considered under three main heads: the littoral benthos (" Uferflora "), 

 the pleuston, and the "Grenzflora" (that is, the flora between low and high 

 w f ater). These main divisions are of course subdivided. The subdivisions 

 of the littoral benthos from deep to shallow water (also in the successional order) 

 are the Characetum, the Potametum, the Nupharetum, the Scirpetum, and the 

 Phragmitetum. It is of interest to note that these associations are still almost 

 entirely natural, in spite of the many centuries of human occupation of the 

 region. The work closes with a short floristic chapter. — H. C. Cowles. 



1 Baumann, Eugen, Die Vegetation des Untersees (Bodensee), eine floristisch- 

 kritische Studie. pp. v+554. pis. 15. figs. jr. Stuttgart: E. Schweizerbartsche 

 Verlagsbuchhandlung. 19 1 1 . 



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