212 HOOKER ON ARCTIC PLANTS, 



possibly lead to the flora of the country of the Tcliutchis being 

 ranked with that of West America. 



The works which have yielded me the most information re- 

 garding this flora are Ledebour's '' Flora Rossica," and the 

 valuable memoirs of Bunge, C. A. Meyer, and Trautvetter on the 

 vegetation of the Taimyr and Boganida Rivers, and on the plants 

 of Jenissei River, in Von MiddendorfTs Siberian " Travels." 

 For their southern extension, Trautvetter and Meyer's "Flora 

 Ochotensis," also in Middendorf's *' Travels " ; Bunge's enu- 

 meration of North-China and Mongolian plants ; Maximovicz's 

 " Flora Amurensis " ; Asa Gray's paper on the botany of Japan 

 (Mem. Amer. Acad. N.S., vi.) ; Karelin and Kiriloff s enumeration 

 of Soongarian plants ; Regel, Bach, and Herder on the East-Siberian 

 and Jakutsk collections of PauUowsky and Von Stubendorff. For 

 the Persian and Indian distribution, I have almost entirely de- 

 pended on the herbarium at Kew, and on Boissier's and Bunge's 

 numerous works. 



3. Arctic West America. — The District thus designated is 

 analogous in position, and to a considerable extent in climate, to 

 the Arctic-European, but is much colder, as is indicated both by 

 the mean temperature and by the position of the June isotherm of 

 41°, which makes an extraordinary bend to the south, nearly to 

 52° N.L., in the longitude of ]3ehring's Straits. 



It extends from Cape Prince-of- Wales, on the east shore of 

 Behring's Straits, to the estuary of the Mackenzie River ; and, as 

 a whole, it differs from the flora of the province to the eastward 

 of it by its far greater number both of European and Asiatic 

 species, by containing various Altai and Siberian plants which do 

 not reach so high a latitude in more western meridians, and by 

 some Temperate plants peculiar to West America. This eastern 

 boundary is, however, quite an artificial one ; for a good many 

 eastern plants cross the Mackenzie and advance westwards to Point 

 Barrow, but which do not extend to Kotzebue's Sound ; and a small 

 colony of Rocky-Mountain plants also spreads eastward and west- 

 wards along the shores of the Arctic Sea, which further tends 

 to connect the floras ; such are Aquilegia brevistylis, Sisymbrium 

 humile, Hutchinsia calycina, Heuchera Richardsonii, Crepis 

 nana, Gentiana arctophila, Salix speciosa, none of which are 

 generally difl'used Arctic plants, or natives of any other parts of 

 Temperate America but the Rocky Mountains. 



The Arctic Circle at Kotzebue's Sound is crossed by the isotherm 

 of 23°, and at the longitude of the Mackenzie by that of 12° 5' ; 

 whilst the June isotherm of 41° ascends obliquely from S.W. ta 

 N.E., from the Aleutian Islands to the mouth of the Mackenzie, 

 and passes south of this province ; the June and the September 

 isotherms of 4J° and 32° both traverse it obliquely, ascending ta 

 the N.E. 



The vast extent of the Pacific Ocean and its warm northerly 

 currents greatly modify the climate of West Arctic America, 

 causing dense fogs to prevail, especially throughout the summer 

 months, whilst the currents keep the ice to the north of Behriug's 



