Stirton. — Description of a new Lichen. 367 



18. Melaspilea metabola, Nyl. 



Section of portion of tliallus with apothecia. 

 a, Ascus with spores, h, Spore. 



19. Squamaria perrugosa, Nyl. (young state. ) 

 Section of portion of thallus with apothecia. 



* Section of apothecia. a, Asciis with spores, h, do. do. c, do. do. 



20. Squamaria perrugosa^ Nyl., var. neglecta, Knight. 

 Ascus with spores. 



Art. LIY. — Description of a new Lichen (Stereocaulon buchanani). 



By James Stirton, M.D.* 



Plate XXV. 



[Head be/ore the Wellington Philosophical Society, 21st November, 1874.] 



A FEW days ago I received from Mr. J. Buchanan of the Colonial Museum, 

 Wellington, a lichen which presents peculiarities of internal organization of 

 sufficient importance to warrant a special notice. As these peculiarities are 

 somewhat anomalous, the absence of spermogonia in the specimens is so far a 

 matter of regret, inasmuch as its generic place is rendered to a certain extent 

 doubtful. 



Of late these secondary organs of fimctification have been occupying 

 considerable attention, and the modifications in size and shape of the sj)ermatia, 

 as well as the comformation and appearance of the spermogonia themselves, 

 have served, in doubtful cases, as a means of discriminating genera, more 

 especially Lecanora from Lecidea. 



The lichen in question occupies an isolated position, and presents affinities 

 to three genera, viz ; — Gomphillus, Stereocaulon and Bceomyces. 



In the extreme length and tenuity of its spores, the former dimension 

 reaching almost the limit, in this respect, amongst lichens ; in the tenacious 

 stiff gelatine which prevades the hymenium, and almost conceals the paraphyses 

 until the appKcation of liq. potasspe, which softens if it does not dissolve this 

 gelatine ; as well as in the presence of longitudinal cavities apart from the 

 thecse, this lichen shows considerable affinities to the curious and anomalous 

 genus Gomphillus. On the other hand the apothecia, in their external 

 conformation and, more especially, in the fact that occasionally very short 

 stipites are present, coated with granules, betray a manifest relationship to 

 Stereocaulon^ with wliich I have meanwhile united it. This relationship is 

 brought out all the more through the variety of St. condensatum, Hffm., where 

 the apothecia are found also sessile on mosses, and have at first sight much 

 the aspect of those of a Lecidea. 



During the current year I detected on Ben Lawers, Perthshire, a form of 



* Dated at Glasgow, 21st September, 1874. 



