270 BOTANY OF PERTH. [November, 



constitution, would seem to indicate that the geological nature 

 or mineral structure of the habitat has frequently more to do 

 with the growth or the geographical distribution of particular 

 species than is usually supposed, for we can scarcely conceive 

 that this gigantic boulder was transferred from the Grampians, 

 — its nearest geologic source, — to its present resting-place, with 

 its present Lichenose coating. On Birnam Hill and the Dunkeld 

 Highlands this species is abundant in a variety of states, gene- 

 rally having a very thick, verrucose, and friable thallus of a 

 leaden-grey tint, along with large symphycarpeous or confluent 

 apothecia. L. varia, in some of its numerous forms, is common 

 on palings and the fences of fields about Muirhall. L. hama- 

 tomma occurs as a white coating of some trappean rocks in a 

 ravine above Kinfauns. I found this Lichen very abundant last 

 summer on North Berwick Law. 



Urceolaria scruposa, var. bryophila, occurs as a coating of 

 Moss above the same rocks on which L. hcematomma and L. tar- 

 tarea grow, in one of the ravines of the Sidlaws. 



Lecidea canescens is found on the tops of walls and on rocks, 

 but I have never found it anywhere in fruit. L. geographica, 

 especially its varieties atro-virens and alpicola, is common on old 

 walls above Corsiehill, Kinnoull, and on the Dunkeld hills. L. 

 atro-alba, var. concentrica of Leighton (Lichenes Britan. Exsic. 

 fasc. i.), is common on the tops of walls on the old Scone road, 

 the apothecia being generally arranged in concentric circles. L. 

 punctata, in some of its varieties, especially var. parasema, is 

 frequent on various trees in the hill-woods, associated usually 

 with various Graphidea or Verrucarics. L. sanguinaria occurs 

 in similar habitats. L. (sruginosa is common as a coating of 

 moist clayey ground on the hill-heaths, as above Muirhall. L. 

 ferruginea is common on walls, as above Corsiehill, Kinnoull. 

 It seems often to be indistinguishable from various other Lecideas, 

 having red or yellow apothecia. 



The Graphidecs are not common in the district. Some of the 

 Arthonias are found associated with Lecideas and Verrucarias 

 on the smooth bark of young Beeches and other trees, but I have 

 not noticed many species of Opegrapha, Gr aphis, and other ge- 

 nera. Where Usneas, Cornicularias, Physcias, and Ranialinas 

 are abundant, the Gi'aphidem appear to be rare, the genera just 

 mentioned usually inhabiting rough barks of trees, such as the 



