257 



(Original %ttkW, 



01^ STIGMATIDIUM DENDRITICUM, Leight. 



By the Rev. "W. A. Leighton, B.A. Camb., F.L.S. 



(Tab. 166.) 



The acute and accurate observations and researches of Mr. Charles 

 Larbalestier, of Jersey, at present residing at Kylemore Castle, Co. 

 Galway, Ireland, have detected many rare and beautiful lichens on 

 the rocks and mountains of Conneoiara, in the immediate neighbonr- 

 hood of his residence. Those he has from time to time transmitted to 

 me for examination and determination. And I would remark how- 

 very close a resemblance they, in a general way, bear to the kinds of 

 lichens I have myself observed throughout ITorth Wales, with an in- 

 termixture of species hitherto gathered only in the north and north- 

 west of Scotland, thus indicating a certain uniformity of geographical 

 distribution. Amongst others he has recently sent me specimens of 

 one which he gathered on shady micaceo-schistose rocks near Einvyle, 

 Co. Galway, and again on similar rocks on the Donoghraagh Moun- 

 tain (alt. 1,800 feet), Kylemore, Co. Galway. This, by its singular and 

 peculiar beauty of appearance, could not fail to arrest and compel 

 special attention. On examination it proves to be a new and very 

 distinct species of Stigmatidium, which may be characteristically 

 named S. dendriticum. It bears the same analogy to S. circumscrip- 

 turn, TayL, as S. venosum, Ach., does to S. crassum, Dub., and can- 

 not in anywise be confounded with any of the other nine or ten species, 

 scattered throughout the world, which at present constitute the genus 

 Stigmatidium of Meyer. Its general appearance is represented in the 

 plate (1) the natural size (2) magnified. The thallus is whitish, or 

 delicately cream-coloured, thin, tartareous, smooth, or occasionally 

 very slightly rimulose, and effuse, consisting, as a vertical section 

 shows, of innumerable colourless, very minute, rounded, granular 

 bodies, easily detached from each other, amidst which are numerous 

 scattered green gonidia of various sizes, rounded or oblong, many with 

 a darker green internal nucleus, as shown at (3). The apothecia are 

 lirellaeform, of a dense black colour, innate, branched in an irregular 

 but exceedingly beautiful dendritical and radiate configuration, gene- 

 rally but not invariably somewhat truncato-bifid at the extremities of 

 the radiations, plane, dilated, naked, and without either thalline or 

 proper margins. In some specimens the lirellae appear to be slightly 

 separated into a more punctiform appearance, whilst in other cases they 

 are decidedly confluent, but presenting a more or less crenulate outline 

 at the edges or margins, forming as it were a transition from punctiform 

 to lirellaeform. The general uniform appearance of the apothecia is 

 N.s. VOL. 4. [September, 1875.] s 



