ASCOLICHENES. 



143 



d. Thallus heteromerous, foliaceous : Parmelia (P. saxatilis ; P. parietina, 

 Wall-Lichen, Fig. 141, is yellow, very frequent on tree-stems, stone-walls, 

 tiles); Physcia (P. ciliaris, 



frequent on tree-stems) ; 

 Sticta (S. pulmonacea, Lung- 

 Lichen, on tree-stems) ; 

 Peltigera, especially on the 

 Moss among trees ; Umbili- 

 caria, on rocks. 



e. Thallus heteromerous, 

 fruticose : Cetraria (G. it- 

 landica, "Iceland Moss," 

 with an olive-brown, flat, 

 furrowed, fringed thallus, 

 on heaths ; C. nivalis, white, 

 in the Polar regions ; 

 Evernia, Ramalina, Usnra 

 (U. barbata, Beard-Lichen, 

 Fig. 143) ; Roccella, Stereo- 

 caulon, Cladonia, of which 

 the genus C. rangiferina, 

 Reindeer- Moss (Fig. 142) is 



important ; Cladonia has two kinds of thallus, one scaly and leaf-like, the other 

 erect, which bears the apothecia and may be fruticose (Fig. 142), or cupular 

 (Fig. 144) ; they grow in soil in forests and on heaths. 



FIG 142. Cladonia rangiferina : s ascocarp 



FIG. 143. Usnea barbata : s ascocarp. (Slightly 

 magnified.) 



FIG. 144. Clndonia pyxidata. 



\V. R. 



