I 62 HERRE 



B. Tips of lobes smooth or barely tomentose; thallus thick, rather 

 rigid 2. rufescens 



BB. Tips of lobes more or less visibly tomentose. 



C. Thallus medium to large, thin 3, canina 



CC. Very thin and papery, expanded 4. canina memhranacea 



I. PELTIGERA SCUTATA (Dicks.) Leight. 



Lichen scutatus Dickson, PI. Crypt. Brit. 3: 18. 1793, excl. S}ni. 

 Peltigera scutata Leighton, Lich. Fl. Grt. Brit. ed. i: 210. 1871. 

 Peltigera scutata Tuck. Syn. N. Am. Lich. I: 107. 1882. 

 Peltigera scutata Herre, Proc. Wash. Acad. Sci. 7: 372. 1906. 



Thallus comparatively thick, small or of medium size, much and 

 irregularly lobed; lobes undulately crenate, their edges confluently 

 gray sorediate; surface smooth, occasionally sorediate; the lobes 

 sometimes finally converted into a powdery sorediate heap, losing 

 all semblance of the original thalline form except marginally; color 

 greenish ashy or gray, or more seldom reddish brown; beneath white, 

 with broad, tomentose, anastomosing, brown veins; these dark 

 brown or blackening centrally and finally coalescing so as to obscure 

 the under surface, which appears only as small white or pale brown 

 spots in the dark area. More or less fibrillose near the margins. 



Apothecia dark reddish-brown to black; spores needle or spindle- 



shaped, straight or bowed, ^-^ ^ P-. 



40 — 61 



On mossy sandstone, tree trunks, and earth. 



Common at all altitudes above 300 feet; reaching its greatest 

 vegetative development on perpendicular mossy sandstone cliffs, 

 where it forms extensive mats, but is usually sterile. Occasionally 

 abundantly fertile, especially on trees, but as a rule apothecia are 

 rare and scattered. A lichen of Europe and North America, no- 

 where abundant according to published records. 



2. PELTIGERA RUFESCENS (Neck.) Hoflfm. 



Lichen rufescens Necker, Meth. Muse. 79. 1771. 

 Peltigera rufescens Hoffmann, Deutsch. Fl. 2 : 107. 1795. 

 Peltigera rufescens Tuck. Syn. N. Am. Lich. I: 108. 1882. 

 Peltigera rufescens Herre, Proc. Wash. Acad. Sci. 7:373. 1906. 



