PAULSON : NOTES ON THE ECOLOGY OF LICHENS. 
2 77 
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 foi 
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 report 8 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 Xck' Phytologist, vol. ix., nos. 3 and 4 (1910). 
