DR. HOOKER ON THE DISTRIBUTION OF ARCTIC PLANTS. 263 



The plants wliich are Avidely distributed in Temperate America or Asia, l3ut almost 

 exclusively Arctic in Europe, are the following : — 



Ranunculus Pallasii, Asia and America. Eritrichium arefioides, Asia and America. 



Trollius Asiaticus, Asia. Gymnandra Pallasii, Asia. 



Parrya macrocarpa, Asia and America. Castilleja pallida, Asia and America. 



arctica, Asia and America. Veronica mncrostemon, Asia. 



Stellaria longipes, Asia and America. Pedicularis Jlammea, America. 



Potentilla emarginata, America. Pinyuicula villosa, Asia and America. 



Epilobium latifolium, Asia and America. Eoeniyia islandica, Asia and America. 



Sedum quadrifidum, Asia. Salix polar is, Asia and America. 



Saxifraga bronchialis, Asia and America. Picea ori.entalis, Asia. 



Senecio resedcefolius, Asia and America. Larix Ledebourii, Asia. 



Ligularia Sibirica, Asia. Platanthera hyperborea, America. 



Mulgedium Sibiricum, Asia. obtusata, America. 



Cassiopeia tetragona, Asia and America. Beyevxia Deschampsioides, Asia and N.W. Ame- 



Gentiana detoiisa, Asia and America. rica. 



Pleurogyne rotata, Asia and America. Dvpontia Fisheri, America. 



The works upon which I have mainly depended for the habitats of the Arctic European 

 plants are Wahlenberg's ' Flora Lapponica,' Ledebour's ' Elora E-ossica,' Fries' ' Summa 

 Vegetabilium Seandinavife,' and ' Mantissge,' and various admirable treatises by Anderssou, 

 Nylander, Hartmann, Lindblom, Wahlberg, Blytt, 0. Martins, E^uprecht, and Schrenk. 



For Spitzbergen plants I have depended on Hooker's enumeration of the Spitzbergen 

 collections made dm-ing Parry's attempt to reach the north pole, Capt. Sabine's collection 

 made in the same island, and on Lindblom and Beilschmied's ' Flora von Spitzbergen ' 

 (Regensburg, Flora, 1842). 



For the southern distribution of the Arctic European plants, I have further consulted 

 Nyman's excellent ' Sylloge,' Ledebour's ' Flora Rossica,' Grisebach's ' Flora Rumelica,' 

 Grenier and Godi^on's ' Flore de France,' Parlatore's 'Flora Italiana,' Koch's 'Synopsis 

 Flor^ Germanise,' Munby's ' Catalogue of Algerian Plants,' A. Richard's of those of 

 Abyssinia, Visiani's 'Flora Dalmatica,' Delile's 'Flora yEgyptiaca,' Boissier's noble 

 ' Voyage Botanique dans I'Espagne,' and Tchihatcheff's ' Asia Minor,' besides numerous 

 Iftcal floras of the Mediterranean regions, Madeira, the Azores, and Canaries. 



2. A7^ctic Asia. — This, which for its extent, contains by far the poorest flora of any 

 on the globe, reaches from the Gulf of Obi eastwards to Behring's Straits, where it merges 

 into the West American. The climate is marked by excessive mean cold ; at the Obi 

 the isotherm of 18° cuts the arctic circle in its S.E. course, and at the eastern extremity 

 of the province the isotherm of 20° cuts the same circle, while the centre part of the 

 district is all north of the isotherm of 9°. The whole of the district is hence far north 

 of the isotherm of 32°, which descends to 52° N.L. in its middle longitude. The extremes 

 of temperature are also very great; the June isotherm of 41° ascending eastward 

 through its Avestern half to the Polar Sea, whilst the September isotherm of 41° descends 

 nearly to 60° N.L. ; whence the low autumn temperature must present an almost insuper- 

 able obstacle to the ripening of seeds within this segment of the polar circle. 



