LICHENS OF SANTA CRUZ PENINSULA 361 



Given by Tuckerman as growing on trees, but with us found 

 as yet only on earth, agreeing thus with Leighton's description : 



Found in some abundance in Pilarcitos Creek Canon, at an 

 altitude of 200-300 feet, growing on high clay banks and on 

 earth in crevices of sandstone cliffs. A few scattered specimens 

 were also found on clay banks beside the road over San Juan 

 Hill, east of Monterey Bay, at an elevation perhaps not far from 

 a thousand feet. This localit}-, however, is just beyond the 

 southern boundary of our territory. 

 Lichen Icuconiclas L. Sp. PI. ed. 2. 2 : 1613. 1763. 

 Physcia Icucomela Michaux, Fl. Bor. Am. 2 : 306. 1S03. 



3. PHYSCIA PULVERULENTA (Schreb.) Nyl. 



Thallus orbiculate or stellate ; the numerous lobes usually 

 long and broad, laciniate, crenate, their margins sometimes dis- 

 sected, tips rounded; central lobes sometimes short, rounded, 

 imbricate, with refuse tips ; color greenish to brownish, the 

 upper surface more or less white pruinose ; beneath black, or 

 marginally white, densely black fibrillose ; medullary layer white 

 or greenish white, apothecia wanting or imperfectly developed. 



On stones in the foothills. 

 Z?V//^;/ ^/^/z'l?;-?^/^;^//^^ Schreber, Spicil. 128. 1771. 

 Physcia ptilveruleiita Nyl. Syn. Meth. Lich. 419. i860. 



4. PHYSCIA PULVERULENTA ARGYPH^A Nyl. 



Thallus orbicular or stellate, appressed ; lobes discrete, nar- 

 row, elongate, many-cleft ; their margins crenate or entire ; 

 usually upturned and confluently sorediate ; thallus often be- 

 coming powdery sorediate or crustose at center, and now disap- 

 pearing, leaving only the marginal lobes. 



Varies from the type in having the thallus of a silvery white 

 color ; rarely darker or dingy. Medullary layer white or 

 greenish white ; apothecia rare ; disk pruinose ; margin thick, 

 sorediate, entire or sometimes slightly dentate; spores 15 x 30 

 mic. 



Common on trees in the foothills and mountains. 

 Physcia pidverulenta argy^hcBa Nyl. 



