20. ACAROSPORACEAE 



Thallus crustose, squamulose, areolate, or subfruticose, occasionally 

 marginally lobed, or entirely obsolete; with fairly complete differentiation 

 into layers or all differentiation lacking, attached to the substratum by 

 hyphal rhizoids or more rarely by an umbilicus. Apothecia circular or 

 irregular in shape, scattered, immersed, adnate, or rarely stipitate, with 

 either a proper or a thalline margin present; asci many-spored; spores 

 very small, hyaline, nonseptate, or rarely 1 -septate, thin walled, with no 

 gelatinous halo. 



Alga Protococcus. 



A. Thallus often obsolete; apothecia with proper margin 43. Biatorella 



A. Thallus present ; apothecia immersed in it ; apothecia with thalline 

 margin 44. Acarospora 



43. Biatorella De Not. Giorn. Bot. Ital. 21 :192. 1846. 

 Thallus crustose, uniform or sublobate at the margins, often thin, scurfy, 

 sometimes granular, evanescent, usually entirely obsolete, no differentia- 

 tion into layers, attached to the substratum by hyphal rhizoids. Apothecia 

 circular or angular, immersed, adnate, or sessile; proper margin present; 

 hypothecium hyaline or brown; paraphyses fragile, thready, rarely 

 branched, sometimes deliquescent; asci many-spored; spores very small, 

 hyaline, nonseptate. 



A. On soil ; apothecia yellow or brown 5. B. fossarum 



A. On rock or trees. 



B. On trees, apothecia dark brown or black 4. B. moriformis 



B. On rock. 



C. Thallus areolate on a black hypothallus 3. B. testudinea 



C. Thallus often obsolete. 



D. Disk pruinose, small 1. B. pruinosa 



D. Disk not pruinose, minute 2. B. simplex 



1. Biatorella pruinosa (Ach.) Mudd, Man. Brit. Lich. 191. 1861. 

 Lichen pruinosa Ach. Lichenogr. Suec. Prodro. 77. 1798. 

 Lecanora privigna var. pruinosa (Ach.) Tuck. 

 Biatorella simplex var. pruinosa (Ach.) Fink. 



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