THE PLANT WORLD. 37 



CONCERNING SAXIFRAGES. 

 \\\ Thos. 1L Kearney, Jr. 



TIlKlvl''. nic some groups of ])lanis wliiGli curry unmistakable 

 cvidc'iicc of oreat ai!«' in tlicir diversity of form and wide distri- 

 hution. 'J1iis is especially true of those genera that are most 

 abundantly represented in liigii noilliern latitudes and on the loftier 

 moinitain systems of the world. 



Such a oroup is the <>enus Saxifraaa, which, if current views of 

 the past history of vegetation are correct, proba))ly originated at some 

 [)()int not far from the Arctic Circle, or, at any rate, made its chief 

 home there in some [);ist era. Then, possibly during the Glacial Epoch, 

 the s[)ecies were forced southward, some to return northward with the 

 retreating ice sheet, others to lind lod«jjment at high altitudes on the 

 mountains. So we find to-day saxifraires al)undant in the alpine and 

 sul)alpine region of the Sierra Nevada, the Rockies, the Pyrenees, 

 Alps, Caucasus, Altai, IIimala3^a and other high'mountains. Only five 

 or six are known from the Cordillera of South America. 



There has been, since the last great scattering of the genus, time 

 for the developinent of })eculiar s})ecies in most of these mountain 

 regions, some of which are very luilike any of the more widely dis- 

 tributed forms. On the other hand some of the most common circum- 

 })olar species recur as alpine plants in many widely separated mountain 

 systems. 



North America is far less rich than Europe in species of this 

 oenus. Eni;ler, in his elaborate monooraph of the o'enus, gives us 

 thirty Hve species, although the numl)er is certainly larger. The 

 mountains of the Western United States are the home of many s{)ecies, 

 some of which are endemic while others are circumpolar and widely 

 distributed alpine species. 



But in northwestern Alaska, on the shores and islands of Bering 

 Sea, Saxifraga is relatively a more important genus than is the case 

 anywhere else in the western hemisphere. Some of the species, as S. JW'l- 

 xoiifdiKi and .V. hriii-f<(ifii, are among the most abundant flowering plants 

 of the region. 



Most impressive is the enormous diversity of form which the 

 species of this genus exhibit. .V. ]>r<ici, afn has leafy stems and itsfew, 

 rather insignificant white flowers are closel\- subtended by leafy bracts. 

 IS. Nelson id /III has crenate orbicular-reniform leaves which are all radi- 



