394 Rev. W. A. Leighton on the British Graphidese. 



same consistence, not carbonaceous, which sometimes is alto- 

 gether wanting, and sometimes gradually tapers off into merely 

 a brown film subtending the base. Nucleus pale yellow, con- 

 sisting of asci and paraphyses. The sporidia sometimes with 

 more septa than seven. 



Plate VII. fig. 28. a. Vertical section of th alius and lirellas ; b. sporidia ; 

 c, upper surface of thallus and lirellae. 



2. Platygramma elaborata. Thallus tartareous, turgescent, 

 smooth ; lirellae immersed, branched, fiexuose, with a thallodal 

 margin ; disk rounded, dilated, naked ; sporidia eight, in asci, 

 acicular, 13-septate, pale yellow. 



Opegrapha venosa, Sm. E. Bot. t. 2454 (1812) — (not Opeg. venosa, Pers., 

 which, according to Eschweiler, Syst. Lich. p. 13. fig. 3, is a true Gra- 

 phis); Hook. Br. Fl. 2. 148. 



Opegraphce atrcs var., Schaer. Spicil. 326 (1836) (in part). 



On beech trees. New Forest, Hampshire ! M?'. Lyell in herb. 

 Borrer. 



Thallus in small, more or less turgescent patches, variable in 

 shape and extent, on the bark of old beech trees (in our speci- 

 mens entirely surrounded by Sagedia aggregata, Fries, and like 

 that plant), apparently limited by a blackish or dark brown mar- 

 gin, irregular and wavy, and variable in breadth, of a dirty 

 cream-colour, smooth, continuous, only slightly cracked here and 

 there, tartareous and of considerable thickness, somewhat de- 

 pressed between the lirellseform apothecia, but forming a pale 

 spurious thallodal margin on a level with and around them. 

 Apothecia imbedded in the thallus in variously branched, flexuose, 

 wavy, slender, very elegant, lirellseform figures, obtuse at the 

 extremities, somewhat rounded and prominent on the surface 

 which is on a level with the thallus,' of a dark red-brown, nearly 

 black, entire and without any proper margin or disk, and there- 

 fore not an Opegrapha. A vertical section shows a pale hyaline 

 nucleus without any apparent tunic or perithecium, slightly 

 darkened on the surface, imbedded in the tartareous thallus. 

 Sporidia eight, in asci, very slender and elongated, more or less 

 acute at each extremity, pale yellow, 13-septate. 



Differs from Sagedia aggregata. Fries, by the sporidia and 

 lirellseform apothecia ; and from Graphis serpentina, of which a 

 state, generally similar, occurs on the same bark, by the different 

 structure of the lirellae and the sporidia. 



Schserer's Exsic. 587 ! Opegrapha crassa, var. venosa, accord- 

 ing to the very imperfect specimen in Mr. Borrer's copy, and 

 which is altogether wanting in mine, is not identical with Pla- 

 tygramma elahoratn, but is a state or variety of Sagedia aggrcgata 



