2 LBCANO-LEOIDBBI [CCENOGONIUM 



2. C. homalotropa A. L. Sm. — Thallus white, smooth, very 

 thin, subdeterminate. Apothecia black, moderate, urceolate, 

 becoming plane, prominent, with a thick elevated margin ; 

 hypothecium thin, blackish ; paraphyses slender, lax, branched 

 above, colourless ; epithecium dusky, subrugose ; spores 8 in the 

 ascus, colourless, elongate-cylindrical, multiseptate, the septa at 

 slightly irregular intervals, 0,130-140 mm. long, 0,0045-50 mm. 

 thick. — Lecidea homalotropa Nyl. in Flora 1. p. 329 (1867) ; 

 Cromb. Lich. Brit. p. 90 ; Leight. Lich. Fl. p. 337 ; ed. 3, p. 361. 



Very closely resembles the preceding, but differs slightly in the 

 apothecia, which are generally plane, larger and somewhat rugose. 



Hab. On the bark of old ash trees. — Bistr. Local and rare in 

 S.W. Ireland. — B. M. Between Killamey and Kenmare, and on the 

 Eagle's Island, Lake of Killamey, Kerry. 



Subtribe V. LECIDEEI Nyl. in Flora Ixv. p. 458 (1882). 



Thallus foliaceous, squamulose, crustaceous or with upright 

 podetia. Apothecia discoid or pateUate, occasionally difform, 

 with proper margin only ; spores usually eight in the ascus, 

 sometimes fewer or numerous. Algal cells (gonidia) Ghloro- 

 phycex. 



The Lecideei differ from the Lecanorei in the absence of any algal 

 cells in the apothecia. There are four British Natural Orders : — 



I. GYEOPHORACE^. — Thallus leafy, expanded. See 

 GtrOPHOBEI (Part I. pp. 321-334). 



II. CLADONIACE^.— ThaUus of two kinds : basal, of leafy 

 equamules, and upright, of simple or branching podetia, which 

 often open out into cup-like expansions (scypihi). See GladODET 

 (Part I. pp. 107-181, 184-186). 



III. CCENOGONIACEiE.— ThaUus filamentous. 



IV. LECIDEACEiE. — Thallus crustaceous or minutely 

 squamulose. 



Order III. CCENOGONIACE-ai. 



Thallus filamentous and byssoid in small patches, or forming 

 widely spreading layers. Apothecia with a proper margin ; asci 

 8-spored; spores colourless, simple or 1-septate. 



Thallus with TrentepohUa gonidia. 68. Coenogonium. 

 Thallus with Cladophora gonidia. 69. Hacodium. 



68. CfflNOGONIUM Ehrenb. in Horse Physicse Berol. p. 120 

 (1820). (PI. 2.) 



Thallus composed of loose branching filaments, usually 

 brightly coloured. Algal cells TrentepoMia, forming a central 



