DR. HOOKER ON THE DISTRIBUTION OF ARCTIC PLANTS. 265 
Picea orientalis. 
Larix Ledebourii 
Cypripedium Calceolus 
Carex ferruginea. 
In other words, of the 233 Asiatic species, 196 are common to Asia and Europe, 
22 are confined to Asia and Europe, 25 are confined to Asia and America only ; and 12 
are confined to Asia, of which 3 are peculiar to the arctic circle. 
The rarity of Gramineae and especially of Cyperacese in this region is its most excep- 
tional feature; only 21 of the 138 arctic species of these orders having hitherto been 
detected in it. Crypt ogamic plants seem to be even more rare ; Woodsia ilvensis and 
Lastrea fragrans being the only Eilices hitherto enumerated. Further researches along 
the edge of the arctic circle would doubtless add more Siberian species to this flora, as 
the examination of the north-east extreme would add American species, and possibly lead 
to the flora of the country of the Tchutchis being ranked with that of West America. 
The works which have yielded me most information regarding this flora, are Ledebour's 
* Mora 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 MiddendorfFs Siberian ■ Travels '. Eor their southern extension Trautvetter and 
Meyer's * Mora Ochotensis,' also in MiddendorfFs * Travels '; Bungc's enumeration of 
North China and Mongolian plants ; Maximovicz's ' Mora Amurensis ;' Asa Gray's 
paper on the botany of Japan (Mem. Amer. Acad. N.S. vi.) ; Karelin and Kiriloff's 
m 
enumeration of Soongarian plants ; Kegel, Bach, and Herder on the East Siberian and 
Jakutsk collections of Paullowsky and Von Stubendorff. For the Persian and Indian 
distribution, I have almost entirely depended 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 Behring'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 spread eastwards 
and westwards along the shores of the Arctic Sea, which further tend to connect the 
floras ; such are Aquilegia brevistylis, Sisymbrium Jmrnile, Sutchinsia calycina, Heuchera 
Rickardsonii, Crepis nana, Gentiana arctophila, Salix speciosa ; none of which are gene- 
rally diffused 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 
