HOOKER ON AKOTIO PLANTS. 



223 



small to yield general results. Especially in determining the 

 influence of temperature in regulating the proportions of the 

 great group of flowering plants, it is of the highest importance to 

 take comprehensive areas, both because of the wider longitudinal 

 dispersion of some orders, especially the Monocotyledons, and the 

 effects of local conditions, such as bog land, which determine the 

 overwhelming preponderance of Cyperacese in some Arctic pro- 

 vinces compared with others. The proportion of genera to 

 species in the whole Arctic phaenogamic, flora is 323 : 762 or 



/Monocot. 1 : 2 



1 • 2*3 



VDicot. 1:2-2 



in the several provinces as follow 



— ), and that of orders to species 1 : 10-8 : 





Gen. 



Gen. to Sp. 



Orders. 



Ord to Sp. 





Arctic Europe 



Asia 



West America 



East America 



Greenland - 



277 

 117 

 172 

 193 

 104 



1:2-3 

 1:2-0 

 1:2-1 

 1:2-5 

 1:2-0 



64 

 38 

 48 

 56 

 38 



1:9-6 

 1:6-1 

 1:7-6 

 1:6-8 

 1:5-5 



Thus Europe presents the most continental character in its 

 Arctic flora and West America the most insular ; which may be 

 attributable to the same cause in both, namely, the uniformity of 

 variety of type. In West America we have, as in an oceanic 

 island, a great mixture of types (Asiatic, European, East and 

 West American) and paucity of species ; in Europe the contrary. 

 The proportions of species to orders are still more various ; but 

 here, again, Europe takes the lead decidedly. The proportions of 

 genera and orders to species of all Greenland differ but little from 

 those of its Arctic regions ; whereas the contrast between Arctic 

 Europe and this, together with Norway as far south as 60° N. lat., 

 is very much greater. This is in accordance with the observation 

 I have elsewhere made, that the whole of Greenland is compara- 

 tively poorer in species than Arctic Greenland is : — 



Gen. Sp. Ord. Sp. 



Arctic Scandinavia - - 1:2*3 1:9*6 



All Scandinavia - - -1:2*8 1 : 11*6 



Arctic Greenland - - 1:2*0 1:5-5 



All Greenland - - -1:2*3 1 : 6*6 



The proportions of Monocotyledons to Dicotyledons are — 



Arctic Flora 

 „ Europe 



Asia 



West America 



East America 



Greenland 



All Greenland 



2*6 

 2*3 

 4*5 

 3*8 

 3*1 

 2*1 

 2-0 



[A Table of the proportion of the largest Orders to the whole 

 Flora (p. 276) is here omitted.] 



