3i8 MESOPHYTES sect, xvi 



These new communities are constantly struggling with one another, and 

 are equally difficult to diagnose and designate. Communities of cultivated 

 plants consist mainly of annual and biennial species, and are likewise 

 mesophytic communities ; but they are not treated in this work.^ 



Shade-plants belonging to the lower storeys of forest and bushland 

 are usually mesophytic in structure. 



Natural mesophytic communities may be classified thus : 



A. COMMUNITIES OF GRASSES' AND HERBS 



1. Arctic and Alpine mat-grassland and mat-herbage. 



2. Meadow. 



3. Pasture on cultivated soil. 



B. COMMUNITIES OF WOODY PLANTS 



1. Mesophytic bushland. 



2. Deciduous dicotylous forest : including monsoon-forest. 



3- Evergreen dicotylous forest: including antarctic forest, sub- 

 tropical rain-forest, tropical rain-forest, palm-forest. 



CHAPTER LXXXVIIL ARCTIC AND ALPINE MAT-GRASSLAND 



AND MAT-HERBAGE 



In Polar countries and above the tree-limit on many mountains there 

 occur on the slopes green tracts of monocotylous and dicotylous herbs. 

 This vegetation, though it may be allied as regards flora to the adjoining 

 fell-fields, nevertheless always includes a number of other species, because 

 the external conditions are more favourable to plant-life. Dwarf-shrubs 

 and undershrubs are absent or rare ; grasses are much more numerous. 



This vegetation reveals itself as a fresh-green, dense covering, which, 

 if it be typical, is also low and soft, and for this reason may be described 

 as mat-vegetation. Roots and rhizomes usually are closely interlaced, so 

 that there arises either a soil tending towards raw humus or one approxi- 

 mating to that of European littoral meadows, with whose vegetation this 

 shows the greatest physiognomic agreement. Among Dicotyledones 

 shoots with broad rosulate leaves are common, presumably in accordance 

 with the low height of the vegetation and the rich supply of light ; this 

 is also true of subglacial communities with which mat-vegetation has 

 other features in common, to wit, deep, pure, floral tints and certain xero- 

 phytic features. The majority of species are perennial. Grasses may 

 preponderate. Amongst them undershrubs are interspersed. Mosses are 

 intermingled in greater or smaller numbers ; but lichens are wanting, or 

 rare and scanty. 



^ A comprehensive survey of formations influenced by man and by grazing 

 animals was published by Bern-a-tzky, 1904. The ' waste-formation ' and its 

 ' associations ' in Nebraska, are discussed by Pounds and Clements, 1 898-1900. Negri, 

 1905, distinguishes in Stazione culturale four ' associations ', and in Stazione ruderale, ] 

 three. 



* The term ' grass ' is here used in a wide, ecological sense, and includes 

 Gramineae, Cyperaceae, Juncaceae, Eriocaulonaceae, Xyridaceae, and similar, 

 mainly tropical, Monocotyledones. 



* 



