46 LICHENS OF THE STATE OF WASHINGTON 



B. Thallus large, cephalodia borne only on the upper surface. 



1. P. aphthosa 



B. Thallus small, cephalodia borne only on the veins of the lower surface, 



2. P. venosa 

 A. Cephalodia absent, thallus does not turn bright green when moist. 



C. Upper surface downy, or bearing trichomatic hyphae. 



D. Lower surface covered with a dense brown to black tomentum. 



6. P. malacea 

 D. Lower surface reticulated with distinct veins. 



E. Veins light brown to black, lighter near the margins. 



F. Bearing coralloid branches, usually on the margins, lobes narrow. 



8. P. praetextata 



F. Not bearing coralloid branches, margins crenate, lobes wider. 



9. P. rufescens 

 E. Veins mostly white, sometimes brownish. 



G. Thallus very small to medium sized. 



H. Bearing masses of soredia on the upper surface, thallus never 



exceeding 2.5 cm. in the largest diameter. 5. P. leptoderma 



H. Never bearing masses of soredia on the upper surface, thallus 



often larger 11. P. spuria 



G. Thallus medium sized to large. 



L Thallus large, upper surface irregularly pitted. 



4. P. canina f. membranacea 

 1. Thallus smaller, upper surface not minutely pitted. 



3. P. canina 

 C. Upper surface granular, bearing soredia on the margins, veins forming 



a close tomentum on the under surface. 10. P. scutata 



C. Upper surface smooth and shiny, thallus digitately lobed ; apothecia 

 borne on narrow digitately clustered lobules, finally revolute. 



7. P. polydactyla 



1. Peltigera aphthosa (L.) Willd. Fl. Berol. Prodro. 347. 1787. Lichen 

 aphthosus Linn. Sp. PI. 1148. 1753. 



Thallus apple green, gray green, or some shade of brown, bright green 

 when wet, medium sized to large, smooth, usually sprinkled with cephalodia, 

 lobes broad, rounded, margins strongly ascending; below cream color or 

 smoky black, reticulated with almost white or purplish veins, bearing scat- 

 tered rhizoids. Apothecia on the tips of somewhat elongated lobules, revo- 

 lute, adnate; disk dark reddish brown, almost black; proper margin, 

 concolorous with the thallus, thin, crenate; asci 8-spored; spores hyaline 

 or brownish, acicular, 3-7-septate, 48.0-75.9 x 4.9-5.2 fx. 



On soil and on moss covered rocks : San Juan Co. : San Juan Island, 

 Friday Harbor, 1928, 2006. Clallam Co.: Lake Sutherland, 590 ft., 1931, 

 1025. King Co.: Richmond Highlands, 300 ft., 1931, 581. Yakima Co.: 

 Deadhorse hill, 4500 ft., 1931, 983. Chelan Co.: Rainbow Trail, 3800 ft, 

 1931, 1264 Pend Oreille Co.: Metaline Falls, 2600 ft., 1931, 1481. San 



