184 



L1CHENACEI. 



[ROCCELLA. 



attaining a length of 6 inches or more. The apothecia are rare in Britain, 

 though numerous when present. They are dirinean in appearance, super- 

 ficial, somewhat prominent, chiefly marginal, with the pruina at length 

 evanescent. The spermogones have the spermatia 0,012-15 mm. long, 

 scarcely 0,001 mm. thick. 



Hal. On rocks in maritime districts. Distr. Local though plentiful 

 where it occurs in the Channel It-lands and in S. England; very rare in 

 the islands of S.W. Ireland. B. M. : St. Ouen's Bay, Beauport Bay, and 

 St. Brelade's Bay, Island of Jersey ; Jerbourg and Petit-Bot Bay, Island 

 of Guernsey. Bolt Head, Devonshire ; Logan Rocks, near Land's End, 

 Tintagel, the Lizard and Lamorna Cove, Cornwall ; St. Mary's, Scilly 

 Islands. 



Tribe VIII. SIPHTILEI Nyl. Mem. Soc. Cherb. v. (1857) 

 p. 97; Syn. i. p. 261. 



Thallus podetiiform, simple or fruticuloso-divided, somewhat 

 tough, usually opaque, often affixed to the substratum by radical 

 branchlets, internally either with a deuse filamentose medulla or 

 fistulose. Apothecia not rightly known. Spermogones (in so far 

 as detected) innate. 



This small tribe is composed of three genera, Siphula, Endoceita, and 

 Thamnolia. The last only is found in Britain. As the apothecia are un- 

 known, the systematic place and even the value of the tribe are somewhat 

 uncertain. Siphula is near to Roccella and Thamnolia to Cladonia. 



35. THAMNOLIA 

 Ach. in litt. 1819, ex 

 Schser. Enum. (1850) 



p. 243. Thallus 



formed of stipites or 

 podetia which are cy- 

 lindrical or somewhat 

 compressed, subulate 

 or coruute, imperfor- 

 ate,simpleor some\v hat 

 branched, acute at the 

 apices, internally fistu- 

 lose ; cortical layer 

 composed of small cells 

 laxly united. Apothe- 

 cia not rightly known. 

 Spermogones innate, 

 pale, with long jointed 

 sterigmata ; spermatia 

 cylindrical, obsoletely 

 thickened at either 

 apex. 



Fig. 38. 



Thamnolia vermicularis Schaer. a. Longitudinal 

 section of tballus, X 200. l>. Vertical section of 

 a spermogone, X 30. c. Sterigmata and sper- 

 matia, XoOO. 



The fistulose podetia and the gonidia ally this to Cladonia ; the sper- 

 mogones are similar to those of Bccomyces, while the continuity of the 



