INTRODUCTION
I n the preparation of P a rt I I . 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 th a t projected by
him in the first volume. Any discrepancies between the sequence
of orders and genera and th a t outlined in the Synopsis in P a rt I.
are explained where they arise. The “ Na tu ra l Orders ” under
which the genera are classified correspond with the “ Families ”
recognised by A. Zahlbruckner in Engler and P ra n tl’s Pflanzen-
familien. In Mr. Crombie’s Synopsis the “ Families ” represent
the first grade of division of the Lichens and are sub-divided into
series, tribes and genera. In P a rt I I . the term “ N atu ral Order ”
has been employed to avoid confusion, and, a t 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 fru it 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, especially to
Dr. Reiidle, Mr. A. Gepp, and Mr. W. Carver, for advice and
assistance generously given during the progress of the work,
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 Mr. B. W. J . Starling. For further new or rare
specimens I am indebted to the Bev. D. Lillie, the Roal W.
Johnson, and the Rev. H. P. Reader, and to Messrs. E. M.
Holmes, J . A. Martindale, J . A. Wheldon and A. Wilson. I
wish also to thank Mr. P. Highley for the care he has shown in
making the drawings for the plates which have been expressly
prepared for this work.
A N N IE LOR RAIN SMITH.