214 



OXYLOPHYTES SECT, vi 



uliginosum var. microphyllum, V. Vitis-Idaea, Ledum palustre f . decum- 

 bens, Arctostaphylos alpina, A. Uva-Ursi, Rhododendron lapponicum, 

 also Diapensia lapponica, Dryas octopetala, Betula nana, B. glandulosa, 

 Juniperus communis, Salix glauca, S. herbacea, and S. polaris ; in Iceland 

 Dryas octopetala may be represented by such numbers of individuals as to 

 form an association, Dryas-heath, and" mingled with it are Silene acaulis, 

 Armeria maritima, Thymus Serpyllum, and others. 1 Several other 

 species may give rise to associations ; in Finland there are Loiseleuria- 

 association, Empetrum-association, Phyllodoce-association 2 and others, 

 which occasionally may occur on fell-fields. 



Herbs, including many evergreen species, grasses, mosses, and lichens 

 are intermixed in greater or smaller numbers, and in many places there 

 are gradual transitions to fell-field, moss-heath, and lichen-heath ; the 

 species are to some extent identical, but their relative abundance is different. 



Dwarf-shrub heath covers large areas in Greenland, North America, 

 and north-eastern Asia. It has provided many arctic travellers with 

 fuel, yet it does not extend to the northernmost land nor to extreme 

 altitudes ; there it is replaced by the more meagre and more easily satisfied 

 fell-field. The soil, as in Europe, is formed of raw humus. 3 



Types intermediate as regards flora between arctic and North German 

 heath occur in Iceland, Lapland, and northern Scandinavia. 4 



Antarctic heath is formed by Acaena adscendens on Kerguelen. On 

 northern and eastern slopes where the atmospheric humidity is high 

 Acaena reigns almost alone on the very humous soil. The creeping 

 main shoots cover the ground with a narrow-meshed net, from which 

 the foliaged shoots rise vertically to a height of half a metre. The habit 

 of the formation is different in situations where the air is less moist. 

 For Acaena then applies itself closely to the soil, and the only erect 

 parts are the shoot-tips and the numerous flowering shoots. Stations 

 of this kind are also characterized by the abundance of companion- 

 plants, such as Lomaria alpina, Azorella, Pringlea, Galium antarcticum, 

 and Ranunculus biternatus. The heath on Kerguelen is the formation 

 which occupies those stations that are the most favourable to plant- 

 life, especially as regards shelter from wind. 5 On South Georgia Acaena 

 adscendens also produces heath. 6 On the Falkland Isles heath consists 

 of a number of dwarf-shrubs, including Empetrum rubrum, Pernettya 

 pumila, Gaultheria microphylla, Drapetes muscosus, Vaccinium Oxycoccos, 

 and Myrtus nummularia. 



CHAPTER LIII. BUSH^AND FOREST ON ACID HUMUS SOIL 



ON bushland allied to dwarf-shrub heath there occur not only species 

 that elsewhere produce high-forest, but also shorter shrubs peculiar to 

 them. , The individual plants are stunted forms, such as have been 

 described on pp. 37 and 129, with bent, contorted stems and branches. 



1 Stefansson, 1894. As to morphology and anatomy, see Warming, 1908 a, and 

 H. E. Petersen, 1908. 



* Hult terms these ' formations '. See also Pohle, 1903. 



3 See Warming, 1887. Gronlund, 1884; Hult, 1887; Brotherus, 1886. 



* Schenck, 1905. Will, 1890. 



