PAULSON : NOTES ON THE ECOLOGY OF LICHENS. 277
around London, for the purpose of collecting data that may help
to a better understanding of the position of lichens in the plant
communities of which they form a part. I have selected certain
units of vegetation and have noted some of the chief features
of lichen-growth in the respective units—as, for instance, number
of species, frequency of occurrence, luxuriance or otherwise of
growth, and the permanent or transitory nature of the species.
Those interested in one or other of the branches of Crypto-
gamic botany must have felt that cryptogams have not been
adequately dealt with in articles and books treating of plant
associations ; for mosses, liverworts, lichens, and fungi are
often entirely omitted from such or are dismissed with a very
brief paragraph.
This omission is not because these plants are unimportant
in differentiating plant-communities, but rather because the
lower plants are not so well known as the higher. Ecology is
one of the youngest branches of biological science and, up to
the present time, the phanerogams and ferns have been much
more fully dealt with.
There is, in the pages of the Essex Naturalist, a wealth of
information respecting the species of cryptogams that form part
of the Forest flora. The specimens have been collected during
the Club's Field Excursions under the guidance of many well
known specialists ; and this information, with some amount
of editing, could be made of considerable value to ecologists.
There is every reason why the Forest area should be treated
exhaustively from the ecological point of view. The area is
well defined ; it is easily accessible to many ; it includes several
plant-associations and centres undergoing rapid change. For
many reasons, therefore, this area ought to become a centre for
ecological work, but this work can scarcely be done by indi-
viduals. It could be carried out only by a small committee
or band of enthusiastic workers.
When the ecological survey of the woodlands of England
was made, the writers of the report8 did not claim to deal with
the subject in detail, but only in a general way ; consequently
the characteristic hornbeam woods of the north London area
received very scant reference. They were included under the
Quercus Robur association ; but, in Types of British Veget-
3 New Phytologist, vol. ix., nos. 3 and 4 (1910).