1914] CURRENT LITERATURE 531 



The body of the work deals with the horizontal and vertical distribution 

 of the species. Of the 200 species, 11 only are rated as arctic, whereas 81 are 

 termed subarctic, and 108 boreal; of the last, 12 are even warm boreal species 

 extending south to the Mediterranean. In considering the vertical distribu- 

 tion, Jonsson terms the upper part of the shore, from the upper limit of algal 

 growth to the low-water mark of neap tide (almost coinciding with the lower 

 limit of the Fucaceae), the upper littoral zone. The lower littoral zone extends 

 from here to the usual low-water mark of spring tide. Then begins the vegeta- 

 tion that is constantly submerged. In the upper littoral zone there are 18 

 reds, 18 browns, 36 greens, and 6 blue-greens; the great bulk of the vegetation, 

 however, is composed of browns. Furthermore, 13 of the reds in the upper 

 littoral zone occur in shaded clefts, being proper to lower zones. In the lower 

 littoral zone there are 39 reds, 37 browns, and 17 greens; the relationship of 

 these is much closer to the submerged species than to the upper littoral species. 

 Of the submerged or sublittoral species, 39 are reds, 22 browns, and 3 greens. 

 It is possible that algae may occur as far down as 80 meters, but they are not 

 abundant below 60 meters. A third of the work is devoted to a detailed 

 account of the numerous algal associations of the three zones noted above, 

 the littoral associations being subdivided into those of the light and of the 

 shade. 



This valuable treatise closes with some notes on the duration of algae and 

 periodical changes. The perennial algae, such as Fucus and Laminar ia, have 

 only a very short period of rest, in spite of the long winter; some species hardly 

 rest at all. Pelvetia caniculata vegetates and fruits the year around. — H. C. 

 Cowles. 



Postglacial changes in German vegetation 



■ 



Hausrath, 3 professor of forestry at Carlsruhe, has issued an extremely 

 useful little book, which gives in compact form a summary of our knowledge 

 regarding landscape and vegetation changes in Germany since the Ice age. 

 One of the author's chief objects is to explain the present landscapes in terms 

 of past conditions. To give proper orientation to the reader, Hausrath 

 presents in brief fashion the ordinary fundamentals of phytogeography, 

 noting the various factors and formations that are in evidence in Germany. 

 It is interesting to note that nearly half the land of Germany is cultivated, 

 one-quarter forest-covered, and one-sixth pasture and meadow. The various 

 views concerning the climate of the Ice age and of subsequent times from the 

 Ice age to the days of the Romans are well set forth, as are the probable stages 

 in the re-establishment of vegetation immediately following the retreat of the 

 glaciers. A chapter is devoted to changes subsequent to Roman occupation, 



J Hausrath, Hans, Pflanzengeographische Wandlungen der deutschen Land- 

 schaft. Wissenschaft und Hypothese XIII. pp. vi + 274. Leipzig: B. G. Teubner. 

 1911. M v 



