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1897 | CURRENT LITERATURE 69 
a study of the mosses in the neighborhood of Smaalen, Norway.”® Mosses 
and other cryptogams are too often omitted or insufficiently considered in 
geographic studies. In this paper are described the various ecological 
factors, the different moss floras and their associations with varying soil con- 
ditions; the mosses are also separated into climatic groups. The prevailing 
rocks are granite, gneiss, and porphyry, the latter especially having a peculiar 
moss flora, largely conditioned by the calcareous nature of the porphyry. 
Grevillius has studied the vegetation of Jerutland near the boundary of N 
way and Sweden.” The author has made a study of the plant societies on 
the various rock types, such as aluminous shales, mica slate, limestone, 
quartzyte, sandstone and granite. The vegetation varies but little as the 
rock varies. The predominant vegetation throughout is the spruce forest 
with abundance of mosses and some birches. Such differences as appear 
where the rocks vary seem to be due largely to the differences in weathering, 
characteristic of the rock types. Sernander and Kjellmark describe the 
results of a peat moor study in the Swedish province of Nerike. % This study 
was prompted by the discovery of two northern species of Betula in the 
moors of Nerike. The paleontological evidence shows that the former flora 
of the region was driven out by an invasion of northern types, the invasion 
being due to increasing severity of climate. A return of more genial con- 
ditions resulted in the retreat of the northern forms; the species of Betula 
now present are taken to be relicts of this northern invasion. Nilsson has 
described coniferous forests in Sweden that have an abundant herbaceous 
vegetation.” Most coniferous forests in Sweden have the soil covered by 
mosses or lichens; in some cases grasses occur, but herbaceous forests have 
seldom been noted. The author describes woods in which there is an abund- 
ance of perennial herbs, grasses and mosses. Such woods are supposed to 
abundant ; it seems likely that the herbs are destined to disappear and that 
the ordinary mossy forest is the ultimate destiny. The author closes with a 
survey of the factors influencing the succession of plant societies ; one of the 
chief causes is the constant change of soil that results from plant life. Each 
species transforms the scil into a substratum that is disadvantageous to itself. 
Wittrock has made a study of the higher epiphytic vegetation of Sweden.” 
*°Det Kgl. Norske Videnskabernes Selskabs Skrifter. No. 1, pp. 1-168. 1896. 
See Bot. Cent. 69: 142- 144. 
7 Sveriges Geologiska Undersikning. Series C, No. 144. 4to. 16 pp. Stock- 
holm, 1895. See Bot. Cent. 69 : 289-290. 
8 Bull. Geol. Inst. Upsala, 2: No. 4. 28 pp. 1895. See Bot. Cent. Bei. 6:57 519. 
9 Tidskrift for wp apeuae PP. 193-209. Stockholm, 1896. See Bot 
Cent. teteg 6:515- 
aa ‘Bergan, Band II, Heft 6, 29 pp. Stockholm, 1896. See Bot. 
ey = 288-28 
