276 The Botanical Gazette. [July, 
narrow margin which gradually disappears with age. 
Lower California, 1892. (7. S. Brandegee.) 
The species north of Mexico may be separated by the fol- 
lowing table in which spore characters, hitherto not recorded, 
are utilized in separating species, although wherever possible 
the characters of the thallus have been employed in order to 
make possible the discrimination of material in the sterile 
condition. iccta bifida and R. Beyrichiana are omitted as 
ea is no recent evidence that they are members of our 
ora. 
Thallus with large air cavities which communicate with the 
upper surface. (SPONGODES Nees.) 
urple rystallina i 
rUpper surface of the thallus mostly smooth bamay rit the jeg 
groove; divisions long, yellowish green. ge rae _ 
Thallus solid, mostly without air cavities \. LACHENODES 
hoff. ) 
a surface of thallus spongy, pitted, green or fie 2% 
le 
2 OSLO 8) SOR See OE 6 0 ee See ee ee 2S eee Le 
Bischo 
a. Thallus without scales or cilia on the margins or Uf 
derneath. 
z. Spores medium size or small (at least under 100/)s 
1. Thallus only slightly reticulate above or not at all. 
* Spores small (60y or less). ; 
Thallus be wide divisions, thin and flat; pariet Reg 
PPUIOGE ie es eek ee ak eee R. te 
Thallus with — divisions. 7 Aust. 
Spores obscurely muriculate..........--++ lee 
Spores snanaly teticulate .. .52 x. Huebeneriana 
* * Spores larger (75-95 /)- ete 
Divisions of me thallus broad; spores nearly opaq derw. 
PevCulstione cs ee ie it Le. tee cous deep 
arvensis 
