30 GUIDE TO CRYPTOGAMS. 



3 a. Thallus not gelatinous when wet. 

 4 a. Thallus fruticulose, alike on all sides. 

 5 a. Thallus with the branches terete, or nearly so. 

 Usnea. Thallus mostly pale green, with the branches trav- 

 ersed by a tough medullar}- cord. Apothecia usually sub-ter- 

 minal, peltate, the margin radiately fibrillose. 



Alectoria. Thallus mostly brown or straw-color, with the 

 branches hollow or filled with a loose cottony medulla. Apo- 

 thecia (rare) lateral, innate sessile, the margin entire. 



5 b. Thallus with the branches compressed. 

 Ramalina. Apothecia sub-pedicillate ; disk pale. 



4 b. Thallus fruticulose or foliaceous, showing a differ- 

 ence between upper and under side (except 

 rarely in Evernia). 



6 a. Apothecia obliquely attached to the tip of a 



branch or lobe. 



Cetraria. Disk colored differently from the thallus. 

 6 b. Apothecia sub-pedicillate. 

 7 a. /Spores ellipsoid or oblong. 

 8 a. Spores simple, colorless. 

 Evernia. Thallus fruticulose or pendulose, softish, with a 

 cottony medulla. 



Parmelia. Thallus foliaceous or foliaceous-fruticulose, mem- 

 branaceous, the medulla comparatively compact. 



8 b. Spores usually polar-bilocular, colorless. 



Theloschistes. Disk yellowish-orange to orange-red. Thal- 

 lus yellowish, greenish or orange, fruticulose or foliaceous. 

 8 c. Sj^ores bi-plurilocular, brown. 



Physcia. Hypothecium white. Thallus foliaceous or frutic- 

 ulose. 



Pyxine. Hypothecium black. Thallus crustaceous-folia- 

 ceous. Apothecia soon becoming convex and black all over, 

 obscuring the exciple. 



7 b. Spores fusiform or acicular. 



Sticta. Thallus foliaceous, mostly ample, frondose and cori- 

 aceous-cartilaginous, often with cyphels below. 



