JOHNSON: A REVISION OF THE SECTION BORAPHILA 21 



been available for study. The range of S. virginiensis is discussed more 

 at length in connection with that species. S. Careyana and S. caroliniana 

 are restricted to a small area in the southern Appalachians, from Tennessee 

 to Georgia, while S. tennesseensis is found only in a small locality in the 

 vicinity of Knoxville, Tennessee. 



Among the western species the most widely distributed is 5". saximontana, 

 which follows the Rocky Mountains from British Columbia to the Yellow- 

 stone Park, with outposts in the Black Hills of South Dakota and in the 

 Wallowa Mountains of eastern Oregon. The remaining species are known 

 only by the type specimen or by scanty specimens from scattering localities, 

 on which no definite statements as to their distribution can be based. 



It is of interest to note that the western species may all be conveniently 

 inscribed within a triangle having its apex in the Black Hills and its base 

 coincident with a line drawn from north of Vancouver Island to the north- 

 east corner of California. The great bulk of the species will be included 

 within the lower (western) half of this triangle. When we add to this popu- 

 lation the species of other sections that are also natives of this region we 

 shall have, undoubtedly, one of the great distribution centers of the genus 

 Saxifraga. 



Key to the Species 



I. Receptacle shallow, contracted 



A. Inflorescence cymose 



1. Filaments subulate 



a. Scapes glabrous, at least above 



(1) Leaves rusty-tomentose beneath S. rufidula 



(2) Leaves glabrous, shallowly dentate towards apex S. laevicaulis 



b. Scapes pubescent, leaves crenate-dentate S. aequidentata 



2. Filaments clavate 



a. Leaves deeply and finely crenate; inflorescence branches filiform 



S. Marshallii 



b. Leaves shallowly crenate, inflorescence stout 



B. Inflorescence paniculate S. Allcnii 



1. Filaments subulate 



a. Sepals reflexed S. Careyana 



b. Sepals spreading S. tennesseensis 



2. Filaments clavate 



a. Follicles slender, elongate -S". caroliniana 



b. Follicles stout 



(1) Petioles much exceeding the b!ades 



(a) Leaves cuneate at the base S. idahoensis 



(b) Leaves truncate or subcordate at the base S, petiolata 



(2) Petioles equalling or shorter than the blades 



(a) Leaves sinuate or repand -S*. Hallit 



(b) Leaves crenate-dentate toward the apex S. microcarpa 



