DR. HOOKER ON THE DISTRIBUTION OF ARCTIC PLANTS. 275 
There are also three plants peculiar to Greenland and Labrador, or 1 lie White or Rocky 
Mountains, which have not hitherto been found elsewhere. They arc : — 
Draba aurea (Rocky Mountains). 
Arenaria Graenlandica (White Mountains and Labrador). 
Potentilla tridentata (Labrador). 
On the Arctic Proportions of Species to Genera, Orders, and Classes. 
The observations which have hitherto been made on this subject, are almost exclusively 
based on data collected on areas too small to yield general results. Especially in deter- 
mining 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 pre- 
ponderance of Cyperacece in some arctic provinces compared with others. 
The proportion of genera to species in the whole arctic phaenogamic flora is 323 : 702, 
_ _ _ Monocot. 1 : 2*8 , ., . ■■ M , . - -„„ . ,, i 
or 1 : 2-3. -p.. , fTo^> ; a orders to species 1 : 10-8; m the several pro- 
follows 
Gen. Gen. to Sp. Orders. Ord. to Sp 
Arctic Europe . . . 277 1:2-3 64 1:9-6 
117 1:2-0 38 1:6-1 
>) 
)> 
Asia 
a 
West America 172 1:21 48 1 : 7*6 
193 1:2-5 56 1 : 68 
East America 
still mor 
„ Greenland 104 1 : 2'0 38 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 or 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 
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 comparatively 
poorer in species than Arctic Greenland is. 
Gen. Sp. Ord. Sp. 
Gen. Sp. Ord. Sp. 
: 5-5 
: 6-6 
Arctic Scandinavia . . . 1 : 2*3 — 1 : 9*6 Arctic Greenland . . . . 1:2-0—1 
All Scandinavia . . . . 1 : 2-8 — 1 : 11'6 All Greenland 1:2-3—1 
The proportions of Monocotyledons to Dicotyledons are : 
Arctic Flora 
Arctic Europe 
„ Asia 
I : 2-6 
1 :2-3 
1 : 4-5 
„ West America 
East America 
1 :38 
» 
» 
1 : 31 
Greenland 
1 : 21 
All Greenland 
1 : 20 
v OL. XXIII 
2P 
