Rev. W. A. Leighton on the British Graphidese. 395 



in which the apothccia have become confluent, and which is fre- 

 quently observable together with the usual state of S. aggregata 

 on many of the. numerous specimens gathered by Mr. Lyell in 

 the New Forest, Hants, existing in Mr. Borrer's herbarium. The 

 sporidia at once show to which plant it belongs, being identical 

 with those of S. aggregata. See Leight. Brit. Angioc. Lich. t. 8. 

 fig. 1. 



Plate VII. fig. 27. a. Vertical section of thallus and apothecia; 6, sporidia. 



I here introduce a plant which exists in Mr. Borrer's herba- 

 rium from " Loughlinstown, Ireland,^' but from whom received 

 he is ignorant, and which I have also detected growing with 

 Opegrapha on young ash near the Sharpstones Hill, Shropshire. 

 T am doubtful whether it should be referred to Platygramma or 

 to Chiodectouy with which latter genus the structure of the apo- 

 thecia greatly assimilates it. I call it provisionallly Chiodecton 

 graphidioides : its description is as follows : — 



Thallus thin, white, tartareous, evanescent. TJiallodal verruccR 

 large and prominent, clustered in groups, round, thick and tar- 

 tareous, of a dirty white or cream colour, smooth, scarcely pul- 

 verulent, marked with irregular rugosities, often from compres- 

 sion in a crowded state forming a cracked continuous crust, 

 very much resembling that of some Graphideae. Apothecia gene- 

 rally one in each verruca, very variable in size and shape, lirel- 

 Iseform, simple or branched, straight or wavy, either acute at the 

 extremities or obtuse and rounded, broad and expanded, blackish- 

 brown, somewhat convex, prominent on the upper surface, slightly 

 shining, but without any trace of pruina or proper margins or 

 disk, though surrounded with a sort of spurious thallodal margin 

 narrow and whitish. A vertical section shows an erect irregu- 

 larly quadrangular dark brown torus penetrating the thallodal 

 verruca, and resting on the thallus or epidermis, bearing on its 

 summit a pale hyaline disciform, flattened or depressed nucleus 

 of paraphyses and,erect narrow obovate asci, surmounted by the 

 dense dark brown veil or disk. Sporidia eight, in each ascus, 

 fusiform, elongated, more or less curved, 3-septate, pale yellow. 



Plate VII. fig. 29. a. Vertical section of thallodal verrucae and apothecia ; 

 h, sporidia, 



[To be continued.] 



