LINDSAY, ON ABROTHALLUS. 29 



their observations. Most of the organisms with which we 

 are now acquainted were noticed and described by them ; and 

 we cannot hokl them altogether responsible for the misinter- 

 pretation of their nature and alliances. 



While studying the furfuraceous and other abnormal states 

 of the thallus of the common Parmelia saxatUis, in various 

 localities in the neighbourhood of Perth, during the past 

 spring, I was struck by a peculiar deformation or anamor- 

 phosis of the thallus, which I first found in abundance on a 

 damp, shady, old wall on Craigie Hill, Perth. An examina- 

 tion of the lichen soon con^dnced me that the deformation 

 was the seat, if it was not also produced by the growth, of 

 a parasitic lichen, and that tliis parasite consisted of the 

 Abrothallus Smithii, A. Welwitzschii, and A. oxysjjorus of 

 Tulasne. The unusual interest connected with this genu.s on 

 many accounts led me to look carefully for it in similar 

 habitats elsewhere. I have since succeeded in finding these 

 species in comparative abundance in many parts both of the 

 Highlands and Lowlands, more especially of the former. I 

 have recently examined microscopically about 250 specimens, 

 chiefly from Highland districts, comprising both species in 

 every state and stage of growth. In the majority of cases 

 the habitat was old roadside walls — chiefly built of rocks or 

 boulders belonging to the primitive or metamorphic series. 

 In a comparatively small number of instances, the matrix 

 grew on loose boulders of the same rocks ; and in a still less 

 number on trees, especially the ash and alder. In all cases 

 the parasites grew on furfiu'aceous forms of P. saxatilis. 

 From the frequency with which I have gathered the Abro- 

 thalli in the Highlands and Lowlands of Scotland, I have no 

 hesitation in asserting that, if carefully looked for, they will 

 probably be found comparatively common in Wales and Ire- 

 land, and — to a less extent perhaps — in England, — especially 

 the hilly parts thereof. In addition to the Abrothalli col- 

 lected by myself, I am indebted to the kindness of the Rev. 

 W. A. Leighton, of Shrewsbury, for specimens, — chiefly of 

 A. oxysporus, growing on Cetraria glauca and Parmelia con- 

 spersa, as well as on P. saxatilis, from Barmouth, North 

 Wales. And lastly, I possess, in Leighton' s ' Lichenes Bri- 

 tannici exsiccati ' (fasc. ii. No. 46), specimens of A. Smithii, 

 Tul., gromng on furfuraceous states of P. saxatilis, from the 

 Wrekin, Shropshire; and (fasc. vi. No. 191) of ^. Welwitz- 

 schii, Mont., on Sticta fuliffinosa, from rocks. New Cut, Mead- 

 fort, Torquay, Devonshire. These specimens have therefore 

 afforded me ample facilities for investigating, by the aid of 

 the microscope and chemical reagents^ the anatomy of the 



