320 MESOPHYTES SECT, xvi 



because it mostly occurs on slopes, herb-slope. 1 It is more widely distributed 

 than typical grassland in Polar countries and on high mountains ; indeed 

 one may encounter communities in which grasses scarcely develop at all. 

 Such richly-flowered, fresh-green herbage occurs commonly in Greenland 

 in sheltered spots, where the soil remains uniformly moist, and not only 

 in the lowlands but sometimes also at considerable altitudes. It is low, 

 dense, and soft, while its perennial herbs are largely rosette plants. 

 In addition to perennial herbs, such dwarf-shrubs as Salix herbacea, 

 S. polaris, and Cassiope hypnoides, are mingled with grasses. Fresh- 

 green mosses, including Hypnum and Aulacomnium, also play a part. 2 

 The same type of community reappears in Iceland, in Scandinavia, and 

 in Finland. 



Oases in Tundra. Oases in tundra obviously represent examples 

 of richly-flowered taller mat-herbage. They have been described by 

 Middendorff 3 as present in Siberia, for instance on the slopes bounding 

 the river Taimyr, where they are sheltered from raw winds and where the 

 soil is a black humus. Caltha palustris, Geum glaciale, species of Poten- 

 tilla, Ranunculus, Polemonium, Eritrichium, Oxytropis, Pedicularis, 

 Saxifraga and Delphinium, and Papaver nudicaule, together with many 

 other tall perennial herbs, with their numerous flowers and gay tints, 

 cause these oases to stand out as bright spots relieving the general desola- 

 tion. Similar vegetation is described by von Baer and Heuglin as occurring 

 in Nova Zembla. Nathorst's slopes 4 on Spitzbergen, Kjellman's flower- 

 field 5 in Siberia, and Pohle's flower-mats 6 in Kanin, are oecologically allied 

 types of vegetation, and perhaps are luxuriant fell-fields. The ' oases ' 

 and the ' flower-carpet ' described respectively by Middendorff and von 

 Baer appear to differ from the mat-herbage of Greenland and the other 

 places mentioned by their taller and less close vegetation, between which 

 one can easily see the dark soil. How rich such herbaceous communities 

 may be is proved by the fact mentioned by Heuglin that in Nova Zembla 

 there were about fifty species of plants growing on a tract only a few square 

 yards in extent. And Stefansson mentions mat-vegetation in the Vatn 

 valley in the north of Iceland, where twenty-four species occurred on 

 a square ell. 



In mat-herbage the leaves of the herbs may be large and luxuriant, 

 as in Alchemilla vulgaris and species of Ranunculus and Potentilla ; this 

 is due to the great atmospheric humidity, the long duration of the weak 

 light, and to the fact that the soil is sheltered, well-lighted, and rich in 

 humus. With the exception of certain species of Gentiana, the species 

 are perennial, and green only during the vegetative season. Concerning 

 growth-forms it may be noted that the caespitose habit with a persistent 

 primary root or with a vertical multicipital root-stock seems to prepon- 

 derate, but that travelling shoots also occur ; we have, however, only 

 little information on these matters. Rosette-shoots are very general. 7 



1 Warming, 1887; Rosenvinge, 1889-90. * Warming, loc. cit., p. 38. 



3 Middendorff, 1867. * ' Sluttningar.' 



5 ' Blomstermark.' * ' Blumenmatten.' 



7 In regard to arctic mat-vegetation, the following works should be consulted : 



Middendorff, 1867; von Baer, 1838; Nathorst, 1883 a; Kjellman, 1882, 1884; 



Warming, 1887; Rosenvinge, 1889; Pohle, 1903 ; Cajander, 1903, 19050; A. Cleve, 



1901; C. Schroter, 1904-8; Brockmann-Jerosch, 1907; Heuglin, 1874; H. Jonsson, 



1905; Stefansson, 1894. 



