104 HERRE 



Serpentine rocks on the coast of California, '(Bolander). Squa- 

 mules less developed than in the last preceding, scarcely lobed. 

 Apothecia originally rufous." 



The above copied from Tuckerman's description in the Synopsis, 

 II: 64. "The last preceding" refers to "Lecidea squalida." 



As yet I have been unable to find the above described lichen, 

 though Bolander 's specimens undoubtedly came from about San 

 Francisco. 



XXIII. Rhizocarpon (Ram.) Th. Fr. 



Rhizocarpon Ramond, in DC. Fl. Fr. 2: 365. 1805, in part. 

 Rhizocarpon Th. Fr. Gen. Heterol. Europ. 92. 1861. 



Thallus uniform crustaceous, without cortex; often with a strongly 

 developed hypothallus. 



Apothecia circular, sessile upon the thallus, innate, or between the 

 areoles, with a black or brown proper margin and a dark hypothe- 

 cium; paraphyses lax, branched and twining; asci with from i to 8 

 spores which are colorless to dark, bilocular to multilocular, or muri- 

 form, with a plainly visible halo. 



Species numerous, on rocks in arctic and temperate regions. 



KEY TO THE SPECIES. 



A . Spores colorless, muriform i. distinctum 



A A. Spores brown, 4-locular to muriform. 

 B. Thallus yeUow. 



C. Thallus sulfur-yellow; medulla with I 2. viridi-atrum 



CC. Thallus lemon-yellow; medulla blue with I.. 3. geographicum 



BB. Thallus not yellow. 



D. Thallus of dark brown or reddish black squamules . .4. bolanderi 

 DD. Thallus more or less gray. 



E. Asci with 2 spores; thallus dark gray and blackening. 



5. geminata 



EE. Asci with 8 spores; thallus brownish, bluish-gray or black- 

 ish gray 6. petraum 



i. RHIZOCARPON DISTINCTUM Th. Fr. 



Rhizocarpon distinctum Th. Fr. Falk. Bleck, 16 (nomen); Lich. 



Scand. 2:625. J 874- 



Thallus sub-determinate to effuse, thin, rimose-areolate, the areo- 

 lae minute to small, slightly concave or flat; hypothallus black; color 

 of plant whitish to leaden gray and darkening; KOH ; CaCl20 2 . 



