BRITISH LICHENS

NOTE TO FIRST EDITION
IN the preparation of Part II. of the Monograph of British Lichens
I have incorporated, as far as possible, the work previously done
by Mr. Crombie, and the classification adopted follows, for the
most part, the main lines of that projected by him in the first
volume. Any discrepancies between the sequence of orders and
genera and that outlined in the Synopsis in Part I. are explained
where they arise. The" Natural Orders" under which the
genera are classified correspond with tho " Families" recognised
by A. Zahlbruckner in Engler and Prantl's "Pfianzenfamilien." In
Mr. Crombie's Synopsis the" Families" represent the first grade
of division of the Lichens and are subdivided into series, tribes
and genera. In Part II. the term" Natural Order" has been
employed to avoid confusion, and, at the same time, to bring the
Monograph into line with recent systematic methods.
According to modern views, more importance is assigned to
the microscopic structure of the fruit than was allowed by
Nylander and Crombie in their scheme of classification. The
systematic value of the form, colour and septation of the spores
had, however, already been recognised by Massalongo and other
continental Lichenologists, and by Mudd in our own country.
I wish to acknowledge my great indebtedness to the Staff of
the Botanical Department of the British Museum with whom I
have been associated during the course of the work and whose
assistance has been most fully given, and to Dr. A. Zahlbruckner,
of Vienna, who has kindly advised me on some points of nomenclature.
I have to thank Mr. A. W. Dennis, who brought to me
the first specimens of Gongylia viridis, collected by 1\1r. B. W. J.
Starling. For further new or rare specimens I am indebted to
the Rev. D. Lillie, the Rev. W. Johnson, and the Rev. H. P.
Reader, and to Messrs. E. M. Holmes, J. A. Martindale, J. A.
vii