Rev. W. A. Leightou on the British Graphidese. 387 



XXXIV. — Momyraph of the British Graphideae. 

 By the Rev. W. A. Leightox, B.A., F.B.S.E. 



[Continued from p. 279.] 



3. Hymeiwdecton. 



Apothecium lirellaeform, immersed ; perithecium a very thin 

 black cartilaginous membrane, entire or surrounding the sides 

 and base; disk broad, plane, surrounded with a very slender 

 proper margin and an accessory thallodal margin. Thallus 

 crustaceous or membranaceous. 



Name from vii-rfv, a membrane, and BeicriKo<t, fitted to receive, 

 in allusion to the membranous structure of the perithecium. 



1. Hymenodecton dendriticum. Thallus tartareous, pulveru- 

 lent, determinate ; lirellje immersed, branched in a pedato-radiate 

 manner ; proper margin very thin ; thallodal margin prominent, 

 rugose; disk plane, dilated, pruinose; sporidia in asci, eight, 

 linear, margined, rounded at the ends, containing about eight 

 transversely oval margined spores. 



Opegrapha dendrUica, Ach. Meth. 31. t. 1. f. 10 (1803) (bad) ; Sra. E. Bot. 



1756 (exceUent); Fries, L. Ref. 372; Hook. Br. Fl. 2. 147. 

 dendritica *, fayl. Fl. Hib. pt. 2. 106 (1836); Schaer. Enum. 152; 



Exs. 58o ' 

 Grapkis dendritica, Ach. L. Univ. 271. (1810) t. 3. fig. 16; Syn. 83. 

 "Arihonia dentritica, Dufoiir, Journ. Phys. 87. 206." (1818) (fide Fries 



et Chevallierj; Chevallier, Fl. de Paris, 1. 294. 

 Opegrapha scripta, ^. dendritica, Schser. Spic. 47. 323(1823-1836). 

 Platygramme dendritica, Meyer in Sprengel Syst. Veg. 4. 1. 254 (1827). 

 Graphis pulverulenta, $. syngrapta, Wallr. Crj'pt. 331 (1831). 



a. Srnithii. Lirellse ramifying at an obtuse angle, extremities 

 acute, thallodal margin prominent. — E. Bot. t. 1756. 



On beech. Sussex ! Mr. Borrer. New Forest, Hampshire ! 

 Mr. Lyell. Cors-y-gedol ! Rev. T. Salwey. Castle Bernard Park, 

 Baudon, Ireland ! Rev. Prof. Hincks. 



Thallus thin, tartareous, pulverulent and cracked, forming 

 large, whitish or pale yellow patches, often with a reddish tinge 

 or glow, circumscribed by a pale watery wavy brown margin or 

 line, the central portion very rugged from the confluent thallodal 

 margins, entirely covered by the crowded lirellfe which cease 

 before reaching the margin, leaving a naked space between them 

 and the wavy line. Lirella very densely crowded in the centre, 

 appearing there through partial obliteration, by reason of com- 

 pression and confusion, as mostly simple or only slightly branched, 

 lanceolate acute at both extremities, towards the margins be- 

 coming less crowded and more distant from each other, repeatedly 



25* 



