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be seen rather commonly in exposed rocky fields, on the ground or 

 sometimes on rotten wood, or scattered over mosses. At first sight 

 it would hardly be associated with Peltigera, but the downy under 

 surface with thickened veins shows its relationship, and serves to 

 distinguish it from Dennatocarpon ininiatum (Group 12) which 

 has a dark under surface with no down nor regular veining. 



Peltigera venosa. Fan Lichen 



Found only occasionally growing on the ground. It is not a 

 rosette-shaped lichen, but consists of irregular, isolated fans, usually 

 less than 2 cm. across, the tips lifted as much as 1 cm. above the 

 soil. The upper surface is smooth, greenish gray or sometimes 

 brownish, the under whitish, conspicuously marked with radiating, 

 dark brown, thickened veins, somewhat downy. Algal cells Pro- 

 tococcus. 



Fruits are frequent, reddish brown, nearly circular, placed on 

 short lobes, or merely on the upper surface of the fans, close to the 

 undulating margins. Spores colorless when mature. 4-celled, 28 to 

 46 by 6 to 10 microns. 



Peltigera venosa is easily distinguished from other species of 

 Peltigera by its small size and fan-like shape, and from all but 

 P. horizontalis by the roundish fruits held nearly horizontal on very 

 short lobes. From P. spuria, also of small size, and sometimes con- 

 sisting of scattered lobes, it is marked by the dark veins of the 

 under surface, those of P. spuria being white or very pale gray. 

 The presence of Protococcus, the bright green algal cells, distin- 

 guishes P. venosa from the other species except P. aphthosa. No 

 other lichen could easily be confused with it. 



Peltigera aphthosa. Studded Leather Lichen 



Growing in deep woods, on mossy banks or rocks, usually at 

 high elevations, but nowhere common. It spreads in irregular 

 rosettes 20 cm. or more across, with lobes up to 5 cm. wide. The 

 upper surface is smooth or wrinkled, olive-green, leather-brown or 

 gray when dry, apple green when moist. The under surface is 

 downy, pale brown or bufi^, with prominent dark brown or blackish, 

 thickened veins, and ragged holdfasts colored like them. Studded 

 over the upper surface are darkening gray, roundish bodies called 



