INTBODUCTION. 



mountain, in Montgomeryshire, but is as plentiful on 

 the carboniferous limestone of the Great Orrne's Head, 

 and flourishes also on the limestone of St. Vincent's 

 rocks, near Bristol ; it is seen also plentifully on the 

 metamorphic rocks at Barinouth. Yet some species 

 evince an affinity not to be mistaken, for Gentiana 

 amarella appears always on calcareous soil, while 

 Digitalis purpurea shrinks carefully from the latter 

 position. I observed this last plant upon Craig 

 Diganwy, an igneous precipitous hill between Conway 

 and the Orme's Head, in 1849, but it disappeared 

 directly I trod the limestone, nor could I discover a 

 single specimen throughout the whole Orme's Head 

 promontory and adjacent calcareous rocks. The 

 following may be considered as more particularly 

 indicating igneous or primitive rock, or to be sought 

 there. 



Corydalis claviculata 

 Arabis petrcea 

 Draba rupestris 

 Galium saxatile 

 Viola lutea 

 Silene acaulis 

 Lychnis viscaria 

 Lychnis alpina 

 Cherleria sedoides 

 Spergula saginoides 

 Moenchia erecta 

 Arenaria verna 

 Cerastium alpinurn 

 Cotyledon umbilicus 

 Rhodiola rosea 

 Sedum album 

 villosum 



Saxifraga umbrosa, and 



allied forms 

 Saxifraga oppositifolia 



stellaris & hypnoides 



Dryas octopetala 

 Alchemilla alpina 

 Hieracium alpinum 

 Veronica saxatilis 

 V. alpina and fruticulosa 

 Digitalis purpurea 

 Antericum serotinum 

 Salix herbacea 

 Luzula arcuata 

 Carex ustulata 

 C. atrata and pulla 

 C. rigida 

 Allosorus crispus 



Some of these are not entirely confined to primitive 

 or volcanic formations, but they may be generally 



