DR. HOOKER ON THE DISTRIBUTION OF ARCTIC PLANTS. 325 



recorded for this plant is the River Kolva in Samoiedland ; but, the precise spot not being 

 indicated by Euprecht, it may not cross the arctic circle. Though a high northern spe- 

 cies, it is not Scandinavian. 



Drtas integrifoUa, Vahl, was originally considered a variety by Chamisso and Schlech- 

 tendal, but is kept distinct in ' Flora Boreali- Americana,' by Torrey and Gray, and Asa 

 Gray. I have, however, vainly endeavoured to find any satisfactory characters for it ; 

 the only one of any consequence, derived from the outline, &c. of the leaf, is not only 

 most inconstant, but presents every transition to D. octopetala. As, however, the most 

 narrow- and entire-leaved forms have been found only in the extreme north, no doubt 

 due to excessive cold, the occurrence of integrifotia on the White Mountains would, if 

 confirmed, be a curious proof of the permanence in a local variety of the most variable 

 of all characters— the development of the leaf. Peck is (according to Pursh) the 

 authority for the United States locality, which wants confirmation. 



Geum strichmi, Ait. This, though kept as a distinct species by Torrey and Gray and 

 all authors, appears to differ from G. urbanmn only in its stout form, and petals longer 

 than the calyx; it is described by American authors as an extremely variable plant. 

 There are other species that might equally well be included ; but the whole genus wants 

 working up. 



SiEVERSiA Immilis, Br. This is scarcely A^'orthy of ranking as a variety of S. Bossii, to 

 which it is reduced by Ledebour and Torrey and Gray. 



RUBTJS jjrojnnquus, Eichardson, is B. arcticits y of Torrey and Gray, distinguished by 

 having flagelliform stems. 



B. acaulis, Mich., is B. arcticus /3, Torrey and Gray, and B. pistlUatits, Smith. 



B. castoreus, Leest. Pries keeps this distinct from arcticus, both being Lapponian. 

 See many excellent remarks on all these species in his ' Summa Veg. Scand.' p. 169 

 Wahlberg makes this a bastard between arcticus and saxatilis, occurring under two forms. 



B. trijlorus, Hook. This Pries regards as a hybrid between saxatilis and castoreus, if 

 I understand aright his system of symbols and nomenclature. Torrey and Gray regard 

 it as a distinct species, as does Asa Gray. Michaux and Seringe both ranked it as a variety 

 of saxatilis. As castoreus and the European form of saxatilis are not found together on 

 the American continent, Pries's view of trijlorus being a hybrid seems untenable. 



PoTENTiLLA Pennsijlvanica, L. Spain is the only European habitat for this plant. P. 

 rubricaulis, Lehm., does not seem to diff'er at all from sericea, L. Torrey and Gray indi- 

 cate numerous varieties of sericea, but keep Pennsylvanica a distinct species. When 

 studying the Himalayan forms of Potentilla, I found it impossible to draw any line between 

 the following varieties of sericea. Viz. Soongarica, Bge., conferta, Bge., multicaulis, Bge., 

 holosericea, Nutt., multifida, L., Pennsijlvanica (3. sfrigosa, and y. Upinnatifula, T. and G. ; 

 and it further appeared to me that P. sericea was connected with nirea by numerous 

 inosculating forms. 



P. nivea, L. I have (under sericea) stated the difficulty of discriminating between this 

 and sericea. The names included under it represent varieties, subspecies, or species. 



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