58 Purple Cliff-Brake 



est, often elongate, often connate at base with segment next 

 below on one or both sides: margins thin, whitish, crenulate, 

 and very minutely and obscurely denticulate: upper surface of 

 ultimate divisions deep bluish-green, glabrous, lower surface 

 pale, minutely paleaceous along midveins: texture coriaceous: 

 rachises and footstocks of ultimate divisions purplish-ebeneous 

 or blackish-red, usually paleaceous. 



Venation pinnate, obscure, free or with occasional areolae: 

 primary branches of midveins once to three times or the basal 

 four times, those above the basal mostly twice forked. 



Sori intramarginal on upper part of veins, becoming conflu- 

 ent laterally: indusia formed of reflexed margin of ultimate 

 divisions of leaf, continuous around sides and apex of division 

 or interrupted at apex: at margin minutely denticulate or undu- 

 late, often finely fluted. 



Spores obscurely tetrahedral, or trivittate. 



Habitat. Dry rocks, especially limestone, exposed to the sun 

 or partly shaded. Often near the tops of cliffs, projecting in 

 masses from cracks in the rock or growing in partly caked sand 

 on the ledges; or on surface rock on hillsides. 



Range. Massachusetts, Vermont, and Ontario to British 

 Columbia and Mackenzie, south to Georgia, Mississippi, Texas, 

 Arizona, and California. 



Pellxa atropurpurea-L.innxus-'Lmk, Fil. Sp. Hort. Berol. 59. 1841. 

 Pteris airopurpurea Linnaeus, Sp. PI. 1076. 1753- 



THE young leaf-blade of Pellcea atropurpurea is simple and 

 roundish or reniform at first (PI. VIII, Fig. i). It then elon- 

 gates and two lobes develop, either simultaneously or succes- 

 sively, at its base (PI. VIII, Fig. 2-5). These lobes are the blade's 



