25 8 PSYCHROPHYTES SECT, ix 



association, Silene acaulis-association ; Ranunculus glacialis-association, 

 Dryas-Potentilla nivea-association. 1 On high Scandinavian mountains 

 parched fell-fields that are poor in humus may take the form of dwarf- 

 shrub heath, 2 which represents a transition to the already mentioned 

 dwarf-shrub heath occurring on raw humus. 3 



Fell-fields of European Mountains. 



On European mountains fell-fields presenting the same physiognomy 

 occur up to the lower limit of perpetual snow and ice, and even higher 

 up, interspersed among the snow-fields, where the sun's rays and slope 

 of the soil bring bare places into existence. On the Alps fell-fields occur 

 both on limestone and on primitive rocks, each of which has its own 

 peculiar species. Particularly in limestone districts one finds accumula- 

 tions of rubble (talus) entertaining a definite herbaceous vegetation ; 

 the plants lie upon bare, periodically very dry rubble, in the form of 

 roundish tufts widely separated from one another and developed on all 

 sides from a single point. In the Tyrolese Alps, according to Kerner, 4 

 such talus is first colonized by some Cruciferae, including Arabis alpina 

 and Hutchinsia alpina, and by species of Saxifraga, Linaria alpina, Salix 

 retusa and S. herbacea, among which are found grasses, sedges, Dryas, 

 and subsequently Loiseleuria procumbens and the two species of Arctosta- 

 phylos. Loiseleuria may here and there acquire mastery over the others 

 and form an association. Mosses and lichens are of less significance than 

 in northern Europe and in Polar lands ; nevertheless Polytrichum septen- 

 trionale plays a great part along all places that have been long covered 

 by moraine-stones. 



The soil tends to a greater extent than in Polar countries to produce 

 xerophytes. The snow-fields on the mountains of Herzegovina, according 

 to G. Beck, 5 in summer have many spring-plants, which it is remarkable 

 to note are partly bulbous and tuberous plants, and include Scilla 

 bifolia, Muscari botryoides, Corydalis tuberosa, Anemone nemorosa, 

 Crocus Heuffelianus, Saxifraga, and Viola. This contrast to the fell-fields 

 of Polar countries must be attributed to greater dryness and heat in 

 summer. 6 



Very many genera are common to arctic countries, alps of the 

 northern hemisphere, and the alps of Java. 7 



Tropical Fell-fields. 



South America. On high mountains in South America we find exten- 

 sive fell-fields, which are termed paramos, in countries ranging from Ecuador 



3 See Hult, 1887, where these are termed formations. 



2 A. Cleve, 1901. 



3 Special reference should be made to the papers by Kihlman (1890), Hult 

 (1887), Warming (1887), Hartz (1895), T. Holm (1887), Nathorst (1883), Kjellman 

 (1882, 1884), G. Andersson (1900, 1902), Porsild (1902), A. Cleve (1901), Sernander 

 (1898), Pohle (1903), C. H. Ostenfeld (19086). 



4 Kerner, 1863. Beck von Mannagetta, 1890, 1901. 



6 Reference should be made to the papers published by Christ (1879), Kerner 

 (1869, 1886), Beck von Mannagetta (1901), Stebler and Schroter (1889, 1892), 

 Schroter, 1904-8, Ottli (1903), and Brockmann-Jerosch (1907). 



1 See Meyen, 1836. 



