676 GEOGEAPHTCAL AND GEOLOGICAL BOTANY. 



1. At least one half of the known species of plants of the tract 

 constituting a botanical region are peculiar to it. ' 



2. A fourth part of the genera of the region are either peculiar 

 to it, or have so decided a maximum that they are comparatively 

 rare in other regions. 



3. The individual Orders of plants are either peculiar to the 

 region or have a decided maximum there. 



Grisebach's regions in many respects correspond with those of 

 Schouw ; each of them is further divided into zones according to 

 altitude above the sea-level up to the line of perpetual snow. The 

 limits of each region are fixed by mountain barriers, the presence of 

 seas, and other impediments physical and climatic, and therefore 

 varying in particular instances. 



1. Region of Mosses and Saxifrages (Arctic- Alpine, or 

 Wahlenberg's Region). 



Mean temperature. Polar regions, 2-41 Fahr. (-17 to -5 C.). 

 Mountains in the south, 21-37 Fahr. (-6 C. to -3 0.). 



This corresponds to Grisebach's Arctic region, and includes those 

 regions which lie beyond the limits of forest vegetation. The period of 

 vegetation only lasts a few weeks, 



Character, Characteristic and predominant genera Ranunculus, Ara- 

 bis, Draba, Arenaria, Dryas, Potentilla, Saxifraga, Rhododendron, Azalea, 

 Gentiana, Pedicularis, Salix, Musci, Lichenes. Of the polar countries 

 especially Coptis, Eutrema, Parrya, Diapensia, Andromeda, Ledum. Of 

 the mountain regions Cherleria, Campanula, Phyteuma, Primula, Aretia, 

 Soldanella. Dwarf perennial herbs with comparatively large ilowers of 

 bright colours. Annuals and trees absent. 



^Predominant shrubs and half-shrubs of the polar countries. Betula nana, 

 Salix herbaceaand other species, Rubus Chamsemorus, Empetrum nigruro, 

 Andromeda hypnoides, A. tetragona, Arbutus alpina, A. Uva ursi, Azalea 

 procumbens, Rhododendron lapponicuin, Menziesia cserulea. 



Predominant shrubs and half -shrubs of the mountains. Juniperus nana, 

 Alnus viridis, Salix reticulata, S. herbacea, Rhododendron ferrugineum, 

 R. hirsutum, R. caucasicum, Vaccinium Myrtillus, V. uliginosum, Azalea 

 procumbens, Arbutus alpina, A. Uva ursi, Empetrum nigrum. 



Plants ivhich approach very closely to tlie snow-line. Ranunculus gla- 

 cialis, Saxifraga oppositifolia, Silene acaulis ; in the polar countries espe- 

 cially, Agrostis algida, Ranunculus hyperboreus, R. nivalis, Saxifraga 

 rivularis, S, cernua, S. nivalis, Papaver nudicaule, Draba alpina, Lychnis 

 apetala, Diapensia lapponica. In the mountain-regions, Saxifraga inus- 

 coides, S. bryoides, Cherleria sedoides, Aretia helvetica, A. alpina, Draba 

 nivalis, Petrocallis pyrenaica, Arabia bellidifolia, Myosotis nana, Gentiana 

 nivalis, Achillea nana, Linaria alpina. No cultivation in this region. 



The flora, as a whole, as tabulated by Hooker, is decidedly Scandinavian. 

 Some of its members are universally diffused throughout the globe, even 

 in the tropics (on mountains) j hence the Scandinavian flora is considered 



