Thallus under 30cm. long... plicata 
= linearis 
Thallus over 30 em. long 5 californica 
Branches naked : : : . subplicata 
Branches spinulose 
Thallus verrucose ’ 
Axis hyaline 
Thallus cinereus. : ; . scoparia 
= dasypoga 
Thallus yellow v. cladoblephara 
Axis rufus . : : : ‘ . variegata 
Thallus papillate—asperate . ; Silipendula 
Primary branches under + mm. diameter 
Thallus smooth . : pete . trichodea 
= filaris 
= incarnata 
== OMEN ED! 
Pachynae 
Chondroid axis } diameter of thalline filament 
Primary branches angulate(KOH +) . . angulata 
Primary branches terete 
With lateral fibrils : ; : ; v. corticata 
Without lateral fibrils (naked) . ; . gracilis 
= lorea? 
Note: U. jamaicensis is indeterminable. 
* Names in black-faced type indicate that species were not described 
from No. America, but are used here only as synonyms in the key. 
24 
