358 THE CANADIAN NATURALIST. [June 



genera are often represented in the temperate regions of two or 

 more continents (and some of them in the south temperate zone 

 also) by closely allied groups of intimately related species. This 

 always complicates matters extremely ; for an arctic species, being 

 generally in a reduced or stunted state, may be equally similar to 

 alpine or reduced forms of what in two or more of these geogra- 

 phically sundered groups may rank as good species, and its 

 affinities and distribution be consequently open to doubt. Thus 

 under the arctic Stellaria longipcs are included five other arctic 

 forms (lo3ta,Fdwardsii,peduncidaris, hebecalyx, and ciliatosepala) ; 

 but amongst these forms some specimens approach closely the 

 American S. Longifolio Muhl., or slight varieties of it ; while 

 others resemble the European S. Friesiana Ser., others S. 

 graminea, others certain Tasmanian forms, and others again 

 Chilian. My own impression is, that some of these may prove 

 but slight modifications of one common, very widely dispersed 

 plant, between all whose varieties no constant definable characters 

 will eventually be found ; but in the present state of science I 

 have abstained from including any of them, because to prove this 

 or disprove it, the whole genus wants a far longer and closer study 

 than it has yet received or than I can give it. Arenarla vema 

 and its forms offer a very parallel case, and these I have included 

 more largely, because I have the published opinion of many 

 botanists to bear me out in doing so. Viola epipsila, palustris 

 and blanda, are thus included, though they are more constant and 

 have to a considerable extent different distributions; because I 

 have found no differences of any moment between their normal 

 forms, because such as exist seem to me to be too slight to attach 

 specific value to, and because, though well distinguished by 

 Scandinavian botanists, they have not been so carefully collected 

 and studied in other parts of the arctic zone. Viola canina, 

 Fragaria vesca, and Sanguisorhia officinalis, afford other ex- 

 amples : all these arctic plants affect the temperate plains rather 

 than the mountains of the northern hemisphere. 



Turning to those arctic plants that chiefly affect the Alps of the 

 temperate or tropical zones, their limitation is quite as difficult ; 

 alpine plants being as proverbially variable as arctic. Many 

 alpine plants are now considered to be only altered forms of low- 

 land ones ; and this affects the estimated distribution of every 

 arctic species that is identified with an alpine one. As an ex- 

 ample, Saxifmga exilis is a very slight variety of S. cernua ; 



