362 HERRE 



5. PHYSCIA PULVERULENTA ISIDIIGERA Zahl- 

 bruckner, subsp. nov. 



" Thallus adpressus, in laciniis marginalibus parcius in cesto 

 thalli dense isidiis subcorallinis, brevibus, tenuibus, fuscis 

 opacis que obsilus," Zahlbruckner in litt. 



Thallus orbicular, marginally closely appressed and thin ; 

 becoming thick, heaped, and isidiose powdery or granular in 

 central portion, all trace of lobes being lost; margin lobes 

 short, crenate, imbricate ; color brownish or dingy black ; often 

 bluish pruinose, the plant then of a pale, bluish slate-color; 

 beneath black, the margin pale ; covered with short black 

 fibrils ; medulla greenish white. Apothecia small ; disk black, 

 occasionally pruinose ; margin thick, tumid, elevated, soredi- 

 ate ; spores 15-20 x 32-37.5 mic. 



On trees, roofs and fences. 



Very common in the lowlands about San Francisco Bay and 

 back to the foothills, growing in great abundance on the shady 

 side exposed to the moist bay winds. Very fine fruiting speci- 

 mens were obtained from an old roof in Mayfield. 



Type, No. 365, Stanford University Herbarium. Cotypes in 

 Royal Botanical Museum, Vienna, in Hasse Herb., and Herre 

 Herb. Type locality, old roof in Mayfield, Cal. 



6. PHYSCIA VENUSTA (Ach.) Nylander. 



Thallus expanded, orbicular, appressed ; lobes many-cleft, 

 narrow, laciniate or crenate, the tips usually rounded ; inner 

 lobes often marked with small tooth-like lobules ; color varying 

 from green through buff to tawny brown ; gray pruinose at 

 least on tips of lobes, but usually otherwise naked; beneath 

 black and densely black fibrillose, usually pale at margin ; 

 medullary layer white. Apothecia pruinose, sessile ; disk flat, 

 black or reddish-black ; often gray or bluish pruinose ; margin 

 thick, entire, fringed with small thalline lobules. Spores 



27-32 "I'C. 



This species grows luxuriantly on oaks, principally ^^ic?-cus 

 chrysolcpis^ along the summit of the range at an altitude of 

 2200 feet and above. 



