THE LICHEN FLORA OF THE SANTA CRUZ PENINSULA 211 



or scattering rhizoids, or growing from the earth; structure radial, 

 sometimes dorso-ventral, with cortex on all sides, formed of hyphae 

 either longitudinal or running at right angles to the surface; in the 

 genus Ramalina strengthened by a so-called inner cortex of distinct 

 and solid cords. Alga Protococcus. 



Apothecia circular, shield or dish-shaped, sessile or sub-pedicellate, 

 with a thalline margin; spores i to 8, colorless, or rarely brown, sim- 

 ple, bilocular, or muriform, thin-walled. 



KEY TO GENERA. 



A. Spores bilocular; cortex strengthened by a mechanical tissue; 

 thallus always compressed more or less, at least basally. 



LV. Ramalina 

 A A . Spores simple. 

 B. Thallus brown or black, like tangled mats of fine hair. 



LIV. Alectoria 



BB. Thallus not black or brown. 



C. Thallus gray or pale straw-color, rarely red; tufted or pen- 

 dulous, becoming enormously elongated; apothecia con- 

 colorous or pale tan, with fibrillose margin. LVI. Usnea 

 CC. Apothecia not concolorous. 

 D. Thallus pendulous or erect, more or less white sorediate; 



sterile LII. Evernia 



DD. Thallus bright lemon-yellow; apothecia chestnut 



LIII. Letharia 



LII. Evernia Ach. 

 Evernia Acharius, Lich. Univ. 84. 1810. 



Thallus erect or pendulous, attached by a holdfast, branched; 

 structure dorso-ventral, the lobes flattened and with a thin cortex on 

 all sides, formed of branching and septate hyphae arranged perpen- 

 dicularly to the surface. 



Apothecia lateral or terminal, sessile or sub-pedicellate, dish-like, 

 with thalline margin, the disk of a different color from the thallus; 

 hypothecium colorless, with an algal layer beneath; paraphyses sim- 

 ple, thick, septate; asci with 8 simple, colorless, small, ellipsoid 

 spores. 



We have one of the two species, widely distributed in the temper- 

 ate zone. 



