( 341 ) 



XIX. A Monograph of the Genus Saxifraga. By Mr. David Don. 

 Communicated by A. B. Lambert, Esq. V.B.L.S. 



Read February 20, 1821. 



J.n the following monograph of a very interesting and difficult 

 genus of plants, my principal object is to endeavour to determine 

 the limits of species on more satisfactory grounds than 1 conceive 

 has hitherto been done. As for six or seven years, during which 

 my attention has been directed to this subject, 1 have had oppor- 

 tunities of cultivating many species of Saxifraga, both foreign 

 and British, and of observing the greater part of the latter in 

 their native habitats, I hope, in some cases at least, to have been 

 enabled to fix on those distinguishing marks which are most 

 constant in determining the species. 



It has been proposed by some botanists to divide Saxifraga 

 into several genera : these subdivisions appear to me, however, 

 to rest on very insufficient grounds ; and that the genus as it now 

 stands, consisting of sections which gradually pass into each 

 other, is truly natural. 



The species of Saxifraga, although most abundant in the 

 higher latitudes, are still very widely extended over the surface 

 of the globe. In the polar regions, many of them are found 

 even near the level of the sea ; and within the tropics, on the 

 summits of the loftiest mountains ; but the cold and elevated 

 regions of the north of Asia, Europe and America are the 

 favourite habitats of the genus. 



vol. xiii. 2 \ I have 



