. 
| 
61 
verna, Aira precow, and A. caryophylla, with small Cerastia, are 
frequent upon them. He must not omit to mention that one moss 
also grew on the ant-hills, for which no European locality was known 
nearer than the ruins of the Colisseum at Rome. On the earth thrown 
out by the rabbit, Echiwm, Cynoglossum, Myosotis, with thistles, the net- 
tle, and the mullein, were enabled to grow. The plants which con- 
stituted the turf were very numerous, a very large proportion of 
Festuca ovina, with a number of other grasses, two species of carex, 
C. glauca and C. praecox. The remainder were generally common to 
upland pastures, excepting certain plants peculiar to the chalk, of 
which, Phytewma crbiculare and the curiously parasitic Thestwm were 
the most deserving of notice. Nearly all the orchids inhabiting the 
south of England found suitable conditions to meet their requirements 
in this turf. 
The thickness of the chalky or ochraceous vegetable loam beneath 
the plants forming the turf, varied from afew inches in the more 
exposed situations, to nearly a foot where the wind had had less 
power. Of the very slow accumulation of this earth, intermixed with 
decayed vegetable matter, the earthworks and burrows on the higher 
Downs showed that only about an inch and a half had been deposited 
since their formation. In these situations, however, the power of the 
wind was so great that all loose particles were swept away into the 
valleys. He must not omit also to mention the circumstance that on 
all these Downs there was no spring or rill carrying water towards the 
sea, nor was there anywhere a place where water stagnated, and 
which would produce a variation in the turf. All the rain being 
immediately absorbed and washing through the turf might carry with 
it the requisite material to dissolve the permeable chalk, in company 
with which it rose in inconsiderable springs on the northern bases of 
the hills, thence to find its way by circuitous channels to the rivers, 
The sea-coast furnished to a great many species of plants the 
conditions which appeared to be essential to their existence: the 
gradual crumbling away of the cliffs and the heaps of shingle, from 
which the sea had retreated, supplied the unoccupied space and broken. 
earth upon which only could they establish themselves. Besides the 
plants which were peculiar to the coast, there were present a number 
of species which, although now everywhere common on inland 
cultivated ground, when near the sea, had always a more robust 
appearance, 
