A BOTANICAL TOUR. 
110 
mits of the rocks, suggesting the idea that a great portion of the flora of the west 
of England may have had its origin from hence. Purton has remarked inci¬ 
dentally, but without founding any conclusion upon it, that many plants of rare 
occurrence in the midland counties, are common in South Wales, and I have 
found this observation to be, in a great measure, correct. Now if, as is generally 
understood, the red sand-stone, and the strata above it, in the order of depo¬ 
sition, still lay beneath the waters at a period posterior to the elevation of these 
carboniferous rocks, they must have derived their vegetation when uncovered, 
from the immigrations of the plants congregated upon this pre-existing dry land. 
Whether, in fact, the very plants upon the rocks here are really indigenous, or 
derived from other countries, it may be now indeed difficult at once to say. The 
origin of plants is a question still undecided, but whether one or many centuries 
of creation are admitted as the most correct theory, it would be unphilosophical 
to assume the gratuitous creation of new plants for any newly immerged land, 
so long as other lands can be proved to have been in existence, from whence vege¬ 
tation could proceed to clothe the bed of the retiring ocean. For as an old wall 
left to the elements is attacked and enveloped by the progeny of the plants around 
it brought by the winds and rains, so in like manner must former newly emerged 
portions of the earth’s surface have received their vegetable colonies from older 
and pre-existing strata of land. All that is required to constitute fit habitats for 
nine-tenths of the phenogamous species in the British Flora, is the sandy sea¬ 
shore, salt-marshes, fresh-water pools and bogs, and limestone eminences, all 
which occur here within a compass of three miles, taking Swansea as the centre. 
I conclude, then, that the great majority of British plants existed on these lime¬ 
stone hills, while a considerable proportion of England was covered by the sea. 
They must, however, have sprung up even here subsequent to the destruction 
of the plants of the coal formation, but whether derived from extraneous sources, 
or created here ab origine^ it is difficult, and perhaps impossible, at present to 
decide. The following plants were all gathered by me upon the carboniferous 
limestone, between the Mumbles, Caswell Bay, and Oystermouth 
^Arabis hirsuta .—'Abundant on the walls of Oystermouth Castle, and at other 
places in the vicinity. Also on the cliffs at Caswell Bay. 
^Arabia turrita .—In the chamber over the Barbican, Oystermouth Castle. 
^Cochlearia danica .—In several of the deserted uncovered apartments of Oys¬ 
termouth Castle. 
^'Lepidium Smithii .—Plentiful about Swansea. 
*Brassica campestris .—Among rubbish near the sea. 
Helianthemum canum .—On the rocks opposite the Mumbles Lighthouse, on 
the mainland. 
Hypericum humifusum .—On the hills towards Caswell Bay, 
