130. Baeomyces ] 34. CLADONIACEAE 241 



small to middle-sized, 0.4-1 mm. across, sometimes clustered, usually immersed 

 in the areoles of the thallus, the disk flat to slightly convex, black, the exciple 

 thin, black, finally disappearing; hypothecium dark brown; asci clavate or inflated- 

 clavate; spores 8, hyaline to dark brown, ellipsoid, 3-7-septate transversely and 

 1-3-septate longitudinally, 17-40X 10-16/*. 



On rocks, throughout northern United States, and southward in the mountains. 



20. Rhizocarpon geographicum (L.) Lam. & DC, Fl. Fr. ed. 3. 2:365. 1815. 

 Lichen geographicus L., Sp. PI. 1140. 1753. Lecidea geographica (L.) Rebent. 



Buellia geographica (L.) Tuck. R. geographicum f. contiguum (Schaer.) 

 Mass. Lecidea geographica var. contigua Schaer. 



Thallus thin to moderately thick, greenish to bright yellow, chinky to some- 

 times areolate or warty, continuous or more commonly scattered upon a conspic- 

 uous black hypothallus; apothecia small to middle-sized, 0.4-1 mm. across, partly 

 immersed between the areoles of the thallus, sometimes clustered and irregular, the 

 disk flat to slightly convex, black, the exciple thin, black, finally disappearing; 

 hypothecium dark brown; asci clavate to inflated-clavate; spores 8, hyaline to 

 dark brown, oblong-ellipsoid, 5-7-septate transversely and 1-3-septate longitudi- 

 nally, 20-38X11-18/*. (Plate 19 6.) 



On rocks, throughout northern United States, and southward in the mountains. 



21. Rhizocarpon oidaleum (Tuck.) Fink, Mycologia 21:306. 1919. 

 Lecidea oidalea Tuck., Proc. Am. Acad. 4:405. 1860. 



Thallus thin, smooth to rough, yellowish to greenish gray or ashy, chinky to 

 minutely areolate, bordered by the black hypothallus; apothecia small to middle- 

 sized, 0.5-1.5 mm. across, sessile, the disk flat to convex, dull black, the exciple 

 thick, black, soon disappearing; hypothecium dark brown; paraphyses semi-distinct, 

 appearing to be branched; asci clavate to inflated-clavate; spores 2-6 or rarely 8, 

 brownish to dark brown, oblong-ellipsoid, 7-11-septate transversely and 2-3-septate 

 longitudinally, 30-78 X 16-24/*. 



On trees, Montana, Washington, Oregon, and California. 



34. CLADONIACEAE 



Thallus commonly twofold, the primary thallus crustose, granulose to squamu- 

 lose, often disappearing soon, showing more or less differentiation and attached 

 to the substratum by hyphal rhizoids, the secondary thallus forming upright podetia, 

 more or less branched, short to elongated and well developed, with or without 

 cortex, solid or hollow within; apothecia round to irregular, scattered or clustered, 

 commonly borne on the tips of the podetia, rarely lateral, with a more or less 

 well-developed exciple. 



The algal host is Pleurococcus. 



A. Podetia short, unbranched 



B. Hypothecium hyaline; spores non- or 1-3-septate .... 130. Baeomyces 

 B. Hypothecium dark; spores non-septate 131. Pilophorus 



A. Podetia short to long, more or less branched 



B. Podetia mostly hollow; spores non-septate 132. Cladonia 



B. Podetia solid; spores 3- or more-septate 133. Stereocaulon 



130. Baeomyces Ehrh., Beitr. Nat. 4:149. 1789. 



Thallus commonly crustose to granulose and sometimes becoming subfoliose, 

 differentiated into a thin upper layer of gelatinized hyphae, distinct algal and 

 medullary layers, and attached to the substratum by hyphal rhizoids; stipes com- 

 posed of loosely interwoven hyphae within and closely packed, longitudinally placed 

 hyphae without; apothecia borne singly or conglomerate on the stipes or very 

 rarely sessile on the thallus, the disk flat to convex, the exciple colored like the 

 disk, often becoming covered; hypothecium hyaline; hymenium hyaline or brown- 



