Caliciei, various Lecideae, Xylographa), (b) As to saxicolous lichens, which occur on rocks and stones, they may be divided into two sections, viz.
Lecanora calcarea, Lecidea calcivora and several Verrucariae), while all other saxicolous lichens may be regarded as belonging to the latter, whatever may be the mineralogical character of the substratum.
Thus in the case of saxicolous lichens the mineralogical character of the rock has of itself little or no influence upon lichen growth, which is influenced more especially and directly by their physical properties, such as their capacity for retaining heat and moisture.
saxicolous lichens in lowland England is available from Ivan Pedley (cost £ 3.00 ).
When I wrote Part 1 I suggested a No. 2 strength except for the soft succulents and epiphytic or saxicolous cacti.