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 Ruprecht, it may not cross the arctic circle. Though a high northern spe- 
cies, it is not Scandinavian. 
Dryas integrifolia, 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. 
Gettm strictum, Ait. This, though kept as a distinct species by Torrey and Gray and 
all authors, appears to differ from G. urbanum 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 % ants 
working up. 
Sieversia humilis, Br. This is scarcely worthy of ranking as a variety of S. Bossii, to 
which it is reduced by Ledebour and Torrey and Gray. 
Rubtts propinquus, Richardson, is B. arcticus y of Torrey and Gray, distinguished by 
having flagelliform stems. 
B. acaulis, Mich., is B. arcticus /3, Torrey and Gray, and B. pistillahts, Smith. 
B. castoreus, Lsest. 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 StaVf/fiJio 
As castoreus and the European form of saxatilis are not found together 
the American continent, Pries' s view of triflorus being a hybrid seems untenable 
Potentilla Pennsylvania, L. Spain is the only European habitat for this plant. P. 
rubricaulis, Lehm., does not seem to differ at aU from sericea, L. Torrey and Gray indi- 
cate numerous varieties of sericea, but keep Pennsylvania 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., 
nolosericea, Nutt, multifida, L., Pennsylvania j3. strigosa, and y. bipinnatrftda, T. and G. ; 
^d it further appeared to me that P. sericea was connected with nivea 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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