Chap. I] CHARACTERS OF THE ARCTIC CLIMATE 683 



leaves, which the hibernating epigeous axes possess/ for instance in many Le- 

 guminosae and Papaver nudicaule. Many plants, however, are devoid of such 

 devices, and in spite of the complete absence of external protection are able 

 to endure the most intense cold, as has been shown in the case of Cochlearia 

 fenestrata l . Such cases are most instructive, for they show that the pro- 

 tection of arctic plants is intrinsic and intracellular, and probably depends 

 on the protoplasm itself. Possibly histological research may throw light on 

 this question. 



Kihlman has disputed even the protection against cold of wilted dry 

 leaves, and has shown that Kjellman's views regarding the necessary economy 

 of material in arctic vegetation are physiologically untenable. 



3. THE FLORISTIC CHARACTER OF THE ARCTIC ZONE. 



The arctic microthermic flora possesses no family peculiar to itself, but is 

 an impoverished repetition of the north temperate mesothermic flora. Green- 

 land, which in its southern parts does not possess a pronounced polar climate, 

 has, according to Warming, 386 species of vascular plants belonging to 53 

 families. These, in order of their number of species, are as follows : Cype- 

 raceae, 56 species ; Gramineae, 50 ; Caryophyllaceae and Cruciferae, 28 each ; 

 Compositae, 22; Rosaceae, 18; Filices, 15; Ranunculaceae, Scrophulariaceae, 

 and Juncaceae, 14 ; Saxifragaceae, 12 ; Ericaceae, 10; Oenotheraceae and 

 Polygonaceae, 7 ; Gentianaceae, Salicaceae, Betulaceae, andLycopodiaceae, 6; 

 Fluvialesand Orchideae, 5 ; Pyrolaceae and Equisetaceae, 4; Halorrhageae, 

 Callitrichaceae, Violaceae, Crassulaceae,Vacciniaceae, and Campanulaceae, 3 ; 

 Papilionaceae, Umbellatae, Plantaginaceae, Primulaceae, Lentibulariaceae, 

 and Rubiaceae, 2 ; Pomaceae, Geraniaceae, Empetraceae, Portulacaceae, Par- 

 nassiaceae, Papaveraceae, Coronaceae, Plumbaginaceae, Polemoniaceae, 

 Boragineae, Labiatae, Diapensiaceae, Caprifoliaceae, Typhaceae, Juncagi- 

 naceae, Colchicaceae, Convallariaceae, Coniferae, and Isoetaceae, 1 2 . 



The decidedly arctic Spitzbergen possesses, according to Nathorst, 192 

 species belonging to 24 families : Compositae, Campanulaceae, Gentianaceae, 

 Scrophulariaceae, Boragineae, Polemoniaceae, Ericaceae, Rosaceae, Saxifra- 

 gaceae, Empetraceae, Cruciferae, Papaveraceae, Ranunculaceae, Caryo- 

 phyllaceae, Polygonaceae, Betulaceae, Salicaceae, Gramineae, Cyperaceae, 

 Juncaceae, Colchicaceae, Polypodiaceae, Lycopodiaceae, Equisetaceae. 

 Gramineae are most richly represented by 23 species, then come, Cruci- 

 ferae, 15; Cyperaceae and Caryophyllaceae, 12; Saxifragaceae, 11; 

 Ranunculaceae, 8. The genera richest in species are Saxifraga and Carex 

 with 10 species, Ranunculus with 8 or 9, Poa with 6, Potentilla with 5. 



1 See p. 39. 



2 Some groups distinguished by Warming as families are usually considered sub- 

 families : Vacciniaceae, Pomaceae, Colchicaceae, Convallariaceae. 



