1857.] BOTANY OF PERTH. 271 



Fir tribe, while the Graphide<B are characteristic of the smoothish 

 barks of large forest-trees in lowland districts. 



Neither the Stereocaulons nor Sph<sropliorons are common in 

 the district, as they are chiefly montane or subalpine species. 

 The small Stereocaulon guisquiliare, Hoff., — the S. nanum of Bri- 

 tish Lichenologists, — occurs on the moist shady rocks of the Uen 

 of Balthayock. S. denudatum also occurs on rocks in various 

 gorges of the Sidlaws. 



Bceomyces roseus occurs on a moist clayey soil on the hill- 

 heaths above Muirhall. This neighbourhood is rich in Cladonias, 

 offering, as it does, abundance of the conditions, terrestrial and 

 aerial, most favourable for their development and growth. They 

 grow chiefly on the moist rotten stumps of old trees, and on 

 moist peaty soil on the hill-heaths or in the hill-woods. It is 

 quite impossible to touch upon the various phases or forms under 

 which the several species of Cladonia occur : this of itself is a 

 labour of no little complexity and extent. Most of the British 

 Cladonias are here met with, of which we may specify C. extensa 

 (the old C. coccifera) , with its bright scarlet apothecia, C. deformis, 

 C. bellidiflora, with its polycephalous apothecia, — one of the most 

 handsome of our common Lichens, — C. pyxidata, C. alcicornis, 

 G. gi'acilis, C. squamosa, C. stellata, var. uncialis, the old C. un- 

 cialis, Cfurcata, often associated with Cetraria aculeata and the 

 next species, C. rangifer'ina, which is common on all the hill- 

 heaths. 



Like the Graphidece, the Verrucai'ias do not seem very com- 

 mon in the district. V. maura occurs on stones on the banks of 

 the Tay, in Invergowrie Bay, and there are a few other lignico- 

 lous and saxicolous species. 



Pertusaria communis is abundant on the exposed roots and 

 lower parts of the trunks of the larger forest-trees. Variolarioid 

 and isidioid conditions however are much more common than 

 fertile states ; the former especially often almost cover the trunks 

 of large trees. In the variolarioid state of the apothecia the 

 soredia are sometimes flat, constituting the Variolaria faginea 

 of the older works on Lichenology, or concave and discoid, form- 

 ing the V. discoidea, or again globular ; in other cases they are 

 sprinkled over the surface of the thallus, converting it, by their 

 confluence, into a white mealy crust. The isidioid condition is 

 sometimes conjoined with the variolarioid. In some of these 



