184 LICHENACEL, [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. 
Hab. On rocks in maritime districts.— Distr. Local though plentiful 
where it occurs in the Channel Islands 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. SIPHULEI Nyl. Mém. 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 dense filamentose medulla or 
fistulose. Apothecia not rightly known. Spermogones (in so far 
as detected) innate. 
This small tribe is composed of three genera, Siphula, Endocena, and 
Thamnolia, The last only is found in Britain. As the apothecia are un- 
known, the systematic place aud even the value of the tribe are somewhat 
uncertain. Stphula is near to Roccella and Thamnolia to Cladonia, 
35. THAMNOLIA 
Ach. in litt. 1819, ex 
Scher. Enum. (1850) 
p. 243. Thallus \ 
formed of stipites or al le 
podetia which are cy- 
lindrical or somewhat 
compressed, subulate 
or cornute, imperfor- 
ate,simpleor somew 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 Thamnolia vermicularis Scher.—a. Longitudinal 
cylindrical, obsoletely section of thallus, x 200. 4. Vertical section of 
thickened at either a spermogone, X 30. c¢. Sterigmata and sper- 
matia, x 500. 
Fig. 38. 
apex. 
The fistulose podetia and the gonidia ally this to Cladonia; the sper- 
mogones are similar to those of Beomyces, while the continuity of the 
