DR, HOOKER ON THE DISTRIBUTION OF ARCTIC PLANTS. 267 



The best marked European and Asiatic species that are not found further east in 

 Temperate or Arctic America are the following : 



Anemone narcissiflora. Spiraea chamaedrifolia. Atriplex littoralis. 



Ranunculus Pallasii. Pyrethrum bipinnatum. Pinus cetnbia. 



Aconitum Napellus. Gentiana prostrata. Carex Norvvegica. 



Parrya macrocarpa. Eritrichium aretioides. Deyeuxia strigosa. 



Dianthus alpinus. Pedicularis verticillata. Langsdoi-ffii. 



Cerastium vulgatum. Primula nivalis. Colpodium fulvum. 



Hence it appears that of the 364 species found in Arctic West America, 319 inhabit 

 East America (arctic or temperate, or both), and 320 are natives of the Old World — a 

 diiference hardly suificient to establish a closer affinity of this flora with one continent 

 rather than with the other. 



The species peculiar to this tract of land are : — 



Braya pilosa. Artemisia androsacea. Salix glacialis. 



Saxifraga Richardsoni. Saussurea subsinuata. 



The rarity of monocotyledons, and especially of the glumaceous orders, is almost as 

 marked a feature of this as of the Asiatic flora : of the 138 arctic species of Glumacece 

 only 54 are natives of West Arctic America. 



The materials for this flora are principally the plants of Chamisso, collected during 

 Kotzebue's voyage, and described by himself and Schlechtendahl ; Lay and Collie's col- 

 lections, described in Beechey's voyage; the ' Elora Boreali- Americana ; ' and Seemann's 

 plants, described in the ' Botany of the Herald.' Most of the above collections are from 

 Behring's Straits. Eor the arctic coast flora I am mainly indebted to Richardson's 

 researches, and to Pullen's and other collections enumerated by Seemann in his account 

 of the flora of Western Eskimo Land. Eor the southern extension of the flora I have had 

 recourse to the ' Elora Boreali- Americana ; ' Ledebour's ' Elora Bossica,' which includes 

 the Sitcha plants ; the American floras of Nuttall, Pursh, Torrey, Gray, &c. ; and to the 

 collections of Drs. Lyall and Wood formed in Vancouver's Island and British Columbia ; 

 for the Californian, Mexican, and Cordillera floras generally, to the herbarium at Kew> 

 the works above mentioned, and the various memoirs of Torrey and of Gray on the plants 

 of the American Surveying Expeditions. 



4. Arctic East America (exclusive of Greenland).— This tract of land is analogous to 

 the Arctic Asiatic in many respects of position and climate, but is very much richer in 

 species. It extends from the estuary of the Mackenzie Biver to Baffin's Bay, and its 

 flora differs from that of the western part of the continent, both in the characters men- 

 tioned in the notice of that province, and in possessing more East American species. 

 The western boundary of this province is an artificial one ; the eastern is very natui-al, 

 both botanically and geographically ; for Baffin's Bay and Davis' Straits (unlike Behring's 

 Strait) have very deep water and different floras on their opposite shores. 



The arctic circle is crossed in the longitude of the Mackenzie River by the isotherm of 

 12°, which thence trends south-eastward to the middle of Hudson's Bay ; and in the longi- 

 tude of Davis' Straits it is crossed by the isotherm of 18^°. The June isotherm of 41° 



VOL. XXIII. 2 o 



