136. Dermatiscum ] 36. ACAROSPORACEAE 277 



3. Umbilicaria pennsylvanica Hoffm., PI. Lich. 3:5. pi. 69, f. 1, 2. 1801. 

 Thallus middle-sized to large, coarsely papillose, ashy to smoky-brown, often 



white-powdery at the center, the margin somewhat irregular, torn; often slightly 

 brownish black and granulose below; apothecia small to middle-sized, 0.5-1.2 mm. 

 across, sessile, round to irregular, the disk flat, black, becoming proliferous, the 

 exciple thin, black, becoming striate and flexuous; spores 1, ellipsoid, becoming 

 blackish brown, 15-23-septate transversely and 7—1 1 -septate longitudinally, 46-70 

 X 23-35 fi. 



On rocks, from Maine to Florida, and westward to Pennsylvania and Tennessee. 



4. Umbilicaria pustulata (L.) Hoffm., Descr. PI. Crypt. 2:13. pi. 28, f. 1,2, pi. 



29, f. 4. 1794. 



Lichen pustulatus L., Sp. PI. 1150. 1753. U. pustulata var. papulosa (Ach.) 

 Tuck. U. dictyiza Nyl. 



Thallus small to middle-sized, papillose, brown or ashy brown, often becoming 

 chinky, often powdery, the margin more or less irregular and sometimes irregularly 

 lobed; grayish to dark brown, granulose and reticulately pitted below; apothecia 

 small to middle-sized, 0.5-1 mm. across, sessile, the disk flat, black, becoming 

 folded, the exciple thin, black, and irregular; spores 1, ellipsoid to oblong-ellipsoid, 

 brown or sometimes hyaline, 9-19-septate transversely and 7-13-septate longitudi- 

 nally, 48-85 X 23-42 /x. (Plate 27 a.) 



On rocks, from Maine to Florida, and westward to Minnesota and New Mex- 

 ico (confined to high elevations southward). 



136. Dermatiscum Nyl., Bot. Zeitung 133. 1867. 



Thallus squamulose to foliose; plectenchymatous cortex poorly developed and 

 pale above, well developed and black below, the medullary region well developed 

 with the hyphae loosely interwoven in the upper part and closely interwoven in 

 the lower part; without rhizoids and attached by a ventral umbilicus; apothecia 

 immersed to superficial, the exciple colored like the disk, often wanting; hypo- 

 thecium hyaline to brown; paraphyses sometimes branched toward the apices; 

 asci cylindrico-clavate; spores 8, brown, 1-septate, somewhat constricted. 



The algal host is Pleurococcus, distributed throughout the medulla, but more 

 abundant in the upper part. 



1. Dermatiscum catawbensis (Willey) Nyl.; Willey, Bull. Torr. Club 14:222. 

 1887. 



Bnellia catawbensis Willey, Int. Stud. Lich. 49. 1887. D. porcellaneum Nyl. 



Thallus foliose, rather thick, whitish, round to somewhat irregular, small, 

 scarcely exceeding 1 cm. across, the margin sometimes obscurely lobed; black 

 below; apothecia small, 0.5-1.3 mm. across, immersed to semisuperficial, scattered 

 or clustered, circular to somewhat irregular in outline, the disk flat, black, the 

 exciple rudimentary or wanting; hvpothecium dark brown; spores oblong-ellipsoid, 

 13-16 X 7.5-8.5 fi. 



On rocks, South Carolina. 



36. ACAROSPORACEAE 



Thallus crustose, scaly or squamulose, devoid of differentiation or showing 

 poorly or well-developed plectenchymatous cortex, rarely plectenchymatous through- 

 out, with algal and poorly developed medullary layers, attached to the substratum 

 by hyphal rhizoids or rarely by an umbilicus; apothecia round, immersed to adnate 

 or rarely somewhat pedicellate, single or aggregate, with proper or thalloid exciple. 



The algal hosts are Pleurococcus and Protococcus. 



A. Horizontal thallus well developed 

 B. Apothecia with thalloid exciple 



C. Apothecia immersed, spores non-septate 140. Acarospora 



