280 THE ESSEX NATURALIST.
loose portions of turf lay scattered over the surface. An explana-
tion for this peculiar condition could not be satisfactorily sug-
gested until a comparatively bare area was discovered which
included large numbers of detached patches of vegetation that
were similar in form and structure, being convex above, under-
cut at the edges, and standing higher than the general level of
the bare sand around them. All stages in the formation of
these patches, from the commencement to the fully-formed
"cupola-like" mass standing upon a slender central pillar
exhibiting root fibres below, were present. There was evidence
that they had been formed by sand blasts, aided in the first stages
by rabbits that had partly destroyed the vegetation.
This part of Farrow's paper is particularly interesting to the
lichenologist from the fact that it notes a retrogression of vegeta-
tion back to the early lichen stage.
Commencing with a cupola during the early stages of its
formation, he found the heath grasses Agrostis vulgaris and
Festuca ovina co-dominant, then, following this stage, Festuca
became the sole dominant. This state was followed by the moss
stage with Campylopus flexuosus and Ceratodon purpureus co-
dominant on the central portion of the upper surface. Last
of all came the lichen stage with Cladonia coccifera, C. cervicornis,
Cetraria aculeata, and Lecidea uliginosa.
Very little had been written about the lichens of the arctic-
alpine vegetation previous to the description of the alpine vegeta-
tion of the mountain Ben-y-Gloe (12). The authors supply
many examples of the adaptation to the severe climate that
such plants endure. Attention is drawn to the stony nature
of the ground, the rapid drainage after heavy rain, and the ab-
sence of soil except in the deep interstices between the stones.
After rainfall there are often intervals of bright sunshine which
cause rapid evaporation from the rock surface so that vegeta-
tion depends to a great extent upon the prevalent cloud-mist,
and for this reason there are special adaptations for securing
water supply, thus, Cerania vermicularis, which is mostly pros-
trate and resembles small white worms upon the ground, turns
up its pointed ends as an attraction to the dew. Many lichens,
like the stunted phanerogams in similar situations, are com-
pact and cushion-like. The only foliaceous Parmelia seen was
P. alpicola, so reduced that it resembled a crustose Lecanora.