CHAP. Lxxxviii MAT- VEGETATION 319 



The mat-vegetation of Polar countries and that of Central European 

 and other mountains display so close an oecological agreement that the 

 two cannot be treated apart. Yet mat-vegetation should perhaps be 

 subdivided into 



Mat-grassland mainly of Gramineae. 



Mat-herbage mainly of dicotylous perennial herbs. 



As a first step towards the formation of mat-vegetation we may re- 

 gard that of the snow-patches} These are, according to C. Schroter,- gently 

 inchned, fiat or concave, spots that occur on mountains and in Polar 

 countries and are saturated with water from melted snow. If they be 

 depressions within which the snow remains lying for a long time, then 

 there is gradually deposited a thick, black, humus, which owes its origin 

 to the snow. For this carries down from the air a quantity of organic 

 dust ; in addition, particles are deposited by the wind ; thus the snow is 

 copiously ' manured '. This habitat is sharply characterized by lowness 

 of temperature, abundance of humus, and permanent saturation of the 

 soil ; and the community of plants settling upon it in Switzerland is 

 extremely constant and is composed of only a few species, and, above all, 

 of Salix herbacea, with which are found Alchemilla pentaphylla, Gnapha- 

 lium supinum, Ligusticum Mutellina, Plantago alpina, species of Soldanella, 

 Sibbaldia procumbens, and others. 



Arctic Mat-grassland. 



In mat-vegetation of arctic countries grasses often preponderate over 

 other Monocotyledones or over Dicotyledones. Brotherus mentions 

 luxuriant mat-grassland in Kola consisting of Poa pratensis and Festuca 

 rubra, in addition to which there are many perennial herbs, including 

 species of Trollius, Ranunculus, Cochlearia, Geranium, Melandryum, and 

 Cerastium, Rubus Chamaemorus and R. arcticus, Cornus suecica, also 

 species of Archangehca, Matricaria, Solidago, and Rhinanthus. Similar 

 mat-grassland is stated to occur in Nova Zembla, and recurs in Greenland, 

 near Eskimo dwelhngs, also in Iceland. On this island cultivation often 

 I has played a part, inasmuch as the application of manure is a factor of 

 great moment. As Thoroddsen says, ' The welfare of the country depends 

 on its grass.' Here the commonest species include Anthoxanthum 

 odoratum, Alopecurus geniculatus, Aira caespitosa, Poa trivialis, P. praten- 

 sis, and Agrostis alba ; there is, of course, an admixture of monocotylous 

 ind dicotylous perennial herbs. 



But travellers do not sharply distinguish between those fields that are 

 mainly clothed with grasses and those that are largely covered with 

 dicotylous herbs. By the term ' pasture ' is obviously meant a field which 

 lias a fresh-green, close, and low vegetation suitable for grazing purposes. 



Mat-herbage. 



In arctic mat-grassland there is probably always a greater or less 

 admixture of monocotylous and dicotylous perennial herbs. Where the 

 dicotylous herbs gain the mastery over the grasses there arises a different 

 type of vegetation which one may designate mat-herbage, herb-field, or, 



' See p. 257. ' C. Schroter, 1904-8. 



