THE LICHEN FLORA OF THE SANTA CRUZ PENINSULA 175 



Sometimes reduced to very small and sparsely scattered scales 

 with only a trace of peripheral lobation, forming then the variety 

 semitensis of Tuck., which I am unable to separate from diffracta, as 

 the two forms seem to grade imperceptibly one into the other. 



A lichen of Europe and North America. 



SECTION EULECANORA Wainio. 



Thallus uniformly crustaceous, areolate or warty, a cortical layer 

 more or less perfectly developed; apothecia sessile. 



5. LECANORA ALBELLA (Pers.) Ach. 



Lichen albellus Persoon in Ust. Ann. Bot. 11 : 18. 1794. 

 Lecanora albella Ach. Vet. Ak. Handl. 137. 1810. 

 Lecanora pallida Tuck. Syn. N. Am. Lich. I: 185. 1882. 



Thallus thin, smooth, whitish or very pale buff-gray, determinate, 

 from orbicular spreading and forming large diffuse patches; KOH 

 yellow, then dark orange-red; CaCyi^ . 



Apothecia usually scattered, medium, plane, pale buff or flesh- 

 colored, naked or grayish or whitish pruinose, the entire margin 

 finally disappearing; paraphyses hardly separate; thecium blue with 



7-5 ~~ IO 

 I, the color soon fading; spores - ,. 



Common on smooth barked trees in the foothills. Generally dis- 

 tributed throughout Europe and North America. 



6. LECANORA ALBELLA CANCRIFORMIS Tuck. 



Lecanora pallida b. cancriformis Tuck. Syn. N. Am. Lich. I: 186. 



1882. 

 Lecanora pallida b. cancriformis Cummings, Williams, and Seymour, 



Lichens Boreali- Americana, no. 51, Berkeley, Calif. 



Thallus sub-orbicular to effuse, at first thin, soon becoming thick 

 and rough or warty; dull ashy gray to dusky; KOH yellow, changing 

 to muddy red or orange; CaCl2O2-. 



Apothecia numerous, medium to large, from plane finally convex 



