141. Pertusaria ] 37. PERTUSARIACEAE 289 



37. PERTUSARIACEAE 



Thallus crustose, showing differentiation into upper and lower cortical layers, 

 algal and medullary layers, attached to the substratum by hyphal rhizoids ; apothecia 

 immersed to adnate, single or clustered, the disk sometimes becoming a sorediate 

 mass, the exciple usually thalloid. 



The algal hosts are Pleurococcus and Protococcus. 



141. Pertusaria Lam. & DC, Fl. Fr. ed. 3. 2:319. 1815. 



Thallus crustose, thin to thick, partly within the substratum, differentiated into 

 a poorly developed, plectenchymatous upper cortex or a thin gelatinized layer of 

 interwoven hyphae, distinct algal and medullary layers, attached to the sub- 

 stratum by hyphal rhizoids; apothecia minute to small, commonly 1-several im- 

 mersed in wartlike elevations of thallus, opening by a small pore or becoming open 

 and disklike, thalloid covering often breaking up into a sorediate mass; hypothecium 

 hyaline; hymenium hyaline or brownish above; paraphyses branched and netlike 

 interwoven; asci clavate or cylindrico-clavate ; spores 1-8, hyaline, ellipsoid or 

 oblong-ellipsoid, non-septate, with thick wall. 



The algal host is Protococcus. 



A. On trees, rocks, and old wood 



B. Spores 1-4 or rarely 8 in an ascus, more than 50 n in length 

 C. Thallus greenish gray to ashy white, brownish or rarely 

 yellowish gray 



D. Spores rarely more than 170 /jl in length 

 E. Margins not swollen or raised 

 F. Spores 1 or 2 in an ascus 



G. Apothecia passing into sorediate heaps 



H. Apothecia 1-several immersed in each wartlike 



elevation 1. P. multipuncta 



H. Apothecia 1 immersed in each wartlike 



elevation 1. P. multipuncta ophthalmiza 



G. Apothecia persistent, ostiole opening into a disk 

 H. Thallus ashy, smooth to chinky ; exciple 



thin 12. P.Finkii 



H. Thallus ashy to brownish, smooth to 

 rough and areolate; exciple thicker, 



irregular 10. P. pustulata 



F. Spores 2-4 or 8 in an ascus 



G. Ostioles minute 8. P. tetrathalamia 



G. Ostioles prominent, or opening into a blackening 



disk 13. p.kioplaca 



E. Margins swollen and raised 14. P. marginata 



D. Spores reaching 200-250 fj. in length 



E. Thallus lighter and zonate toward the circumference; 



disk becoming sorediate 4. P. velata 



E. Thallus rarely zonate, wartlike elevations often 



crowded 15. p. pertusa 



C. Thallus sulphur-colored to more or less yellowish gray 

 D. Thallus yellow to ashy or yellowish gray 



E. Thallus smooth to wrinkled, minutely areolate or 

 granulose 



F. Disk white-pruinose to pale flesh-colored .... 2. P. lecanina 

 F. Disk dull black or blackish pruinose .... 2. P. lecanina nigra 

 E. Thallus becoming minutely granulose and powdery . 11. P. lutescens 

 D. Thallus sulphur-colored or ashy yellow 



E. On trees; disk blackish, exciple thick, wavy to 



flexuous 16. p.Wulfenii 



E. On rocks; disk yellowish pruinose to blackish, 



exciple thinner 3. P. flavicunda 



B. Spores 8 in an ascus, less than 50 n in length 



C. On trees; disk flesh-colored to greenish or grayish pruinose 



