platygrapha] arthoniacb^ 205 



Aoharius subsequently referred it (Lich. Univ. p. 355) ; the name 

 periclea has been assigned to L. exigua by several British authors 

 (of. Part I. p. 395). The spermogones have been described as 

 Pyrenothea stictica Fr. in Vet. Ak. Handl. 1821, p. 334. 



Hab. On the trunks of old oaks and firs in upland tracts of 

 mountainous districts. — Distr. Only very sparingly in N.W. England 

 (near Kendal, Westmoreland) and the N. Grampians, Scotland; no 

 doubt to be detected elsewhere. — B. M. Near Old Mar Lodge, 

 Braemar, Aberdeenshire. 



2. P. rimata Nyl. II. c. — Thallus effuse, thin, warted and 

 cracked, whitish. Apothecia impressed in the verrucas, simple or 

 divided, variously difform, plane or slightly convex, unequal, 

 blackish, somewhat shining, with a narrow spurious thalline 

 margin ; hypothecium thick, brownish-black ; spores narrowly 

 fusiform, 3-septate, more or less curved, 0,024-34 mm. long, 

 about 0,003-4 mm. thick ; hymenial gelatine bluish then wine- 

 reddish with iodine. — Mudd Man. p. 244, t. 4, f. 95 ; Cromb. 

 Lich. Brit. p. 101; Leight. Lich. Fl. p. 388; ed. 3, p. 411. 

 Schismatomma dolosum var. rimatum Plot. Lich. Exs. n. 438b 

 (1829) fide Nyl. in Act. Soc. Linn. Bord. Z. c. Ghiodecton 

 graphidioides Leight. in Ann. Mag. Nat. Hist. ser. 2, xiii. 

 p. 395, t. 7, f. 29 (1854). 



Differs from the preceding in the verruculose thallus. The 

 verrucse are somewhat large, prominent, aggregate and wrinkled. 

 The apothecia, which are usually one in each verruca, are rather 

 variable in size and form, being sometimes linear and slightly 

 branched. In the very few British specimens seen the spermogones, 

 rarely present, have the spermatia somewhat arcuate, 0,004-5 mm. 

 long. 



Hab. On trunks of trees, ash and elm, in upland wooded situations. 

 — Distr. Local and scarce in W. England, N. Wales and Ireland 

 (Loughlinstown, Dublin). — B. M. Near Sharpstones Hill, Shropshire; 

 Chirk Castle Park, Denbighshire. 



AETHONIACEJE. 



Thallus crustaceous, thin, often developed under the bark 

 (hypophloeodal), evanescent or wanting. Apothecia roundish or 

 difform (ardellse) or elongate (lirellse) ; ascus short, pyriform ; 

 spores 4 to 8 in the ascus, septate or muriform ; paraphyses 

 branched, confluent ; spermogones with simple sterigmata and 

 ovate, cylindrical or slender spermatia. 



The order is throughout distinguished by the immarginate 

 apothecia which often resemble a small spot or stain on the bark, and 

 by the short pyriform asci. It is represented in Britain by two 

 genera : — 



Spores 1- or pluri-septate 83. Arthonia. 



Spores septate and muriform 84. Arthothelium. 



