320 DR. HOOKER ON THE DISTRIBUTION OF ARCTIC PLANTS. 



Thlaspi montcmimi, L. I am quite unable to satisfy myself about the specific limits 

 of this plant, and indeed of many other forms of the genus, whose species appear to be 

 extravagantly miiltiplied. Belgium is its northern limit in Europe, whereas T. alpestre, 

 to which the American plant may belong, reaches Gothland. 



Lepiditjm rtiderale, L. This widely-spread plant advances beyond the arctic circle in 

 North-eastern America, but apparently not in West America or Europe. It is so fre- 

 quently an introduced plant, that it is difficult to assign its indigenous limits. 



SuBULARiA aquatica, L., though apparently not a native of the Alps, is found in the 

 Pyrenees. 



YioIjA. palustris, L. According to Eries, the typical plant of this name is rare and local 

 in Lapland. Asa Gray identifies the White Mountain plant with it ; and it is also found 

 in Southern Greenland. It is absent in Arctic Russia. 



V. epijjsila, Led. Eries, in his 'Novitise,' makes this a variety of palustris ; and in his 

 ' Summa Veg. Scand.' it is regarded as a species found throughout Lapland. Koch 

 keeps it distinct, but has never seen living specimens. Ruprecht (Elor. Samojed. 

 Cisural.) mentions a variety hyperhorea, in which the sepals are narrower and sharper 

 than in the typical states, and the peduncles and petioles more slender. In the in- 

 terior of the arctic Island of Kolgujew it is very rare, and has glabrous leaves. 

 V. hlanda, Wahl. I am doubtful about the specific distinctness of this plant. It closely 

 resembles V. palustris ; and A. Gray keeps it distinct, but his differential characters 

 appear very trifling. In ' Elora Bor.-Am.' the flowers of the two are said to present 

 " the most perfect agreement." In ' Bot. Beechey's Voy.,' V. hlanda is said to inhabit 

 Kotzebue's Sound; and Ledebour, who has seen specimens, retains it with a query, 

 and says that, though allied to V. 2:)alnstris and epipsila, it differs in habit, smaller 

 flowers, and approximate nodes of the root. Seemann does not include it in his Elora 

 of Western Eskimo-land. The hlanda is said to be fragrant. V. tdiginosa, Schrad., 

 is another species which is so excessively close to j^alustris as to be with difficulty 

 distinguishable. 

 T'. microceras, Rupr., is founded on a solitary specimen from the shores of Kolgujew 

 Island ; its author says of it, " fades tota V. p)alustris, sed foUa margine et pagina 

 superiore (non inferiore) pubescentia ; sepala linearia, acuta, margine rigide ciliata, 

 serrata." 

 Viola canina, L. The various forms and near allies of this plant are sources of infinite 

 diversity of opinion amongst botanists ; added to which, regarding canina and its allies 

 as a group designated Sylvestres by Eries, they seem to inosculate in many points with 

 another and different one, the Pratenses, Eries. Thus it is not difficult to unite canina with 

 Buppii and stagnina, through the forms of what is often called lactea. Watson has some 

 excellent remarks on these forms; he includes lactea, Sm., under Jlavicornis, and keeps it 

 doubtfully distinct from canina. Eries considers montana, L., a distinct variety only of 

 canina, and gives all Lapland as the habitat for both, whereas arenaria and sylvatica, 

 though also Lapponian, are more local : in his ' Novitise ' he makes sijlvestris, Lam., a 

 variety of canv)ia, as does De Gingins in DeCandoUe's ' Prodromus.' Koch makes both 



