Systematic studies on the lichen genus Alectoria ach. with particular reference to the British species.

A historical account of the lichen genus Alectoria Ach. from pre-Linnean to modern authors is given. The anatomy and morphology of the genus as a whole are described and in this the scanning electron microscope gave valuable assistance. The lichen acids of the genus have been investigated, and the taxonomic treatment of chemical races in lichens in general is reviewed and a working hypothesis suggested. A cluster-analysis numerical taxonomic study of 47 taxa of Alectoria and 8 species from allied genera, using both chemical and morphological characters, proved useful in the construction of a supraspecific classification of the genus. Four subgenera, Alectoria, Bryopogon (Link)Massal., Sulcata (Du Rietz)D.Hawksw., and Tortuosa D.Hawksw. are recognised, of which Bryopogon is subdivided into five sections. The relationships of the genus to other genera of lichens are discussed. A detailed account of the nomenclature, variability, ecology, and distribution of the British species shows that the following taxa occur in Britain:- A. bicolor (Ehrh.)Nyl. (incl. f. melaneira (Ach.)Nyl.), A. capillaris (Ach.)Cromb. (incl. f. fuscidula (Arnold)D.Hawksw.), A. chalybeiformis (L.)Gray (incl. f. prostrat-eosteola (Gyeln.)D.Hawksw.), A. fuscescens Gyeln. (incl. f. pallida (Savicz)D.Hawksw., var. canescens Bystrek, var. positiva (Gyeln.)D. Hawksw.), A. lanestris (Ach.)Gyeln., A. nigricans (Ach.)Nyl. (incl. f. subchalybeiformis Ras.), A. nitidula (Th.Pr.)Vain., A. ochroleuca (Hoffm.)Massal. (incl. var. citrina (Ras.)D. Hawksw.), A. pseudofuscescens Gyeln., A. pubescens (L.)Howe (incl. f. subciliata (Nyl.)D.Hawksw.), A. sarmentosa (Ach.) Ach. (incl. subsp. sarmentosa and subsp. vexillifera (Nyl.)D. Hawksw.), A. smithii Du Rietz, and A. subcana (Nyl. ex Stizenb.) Gyeln.. A revised check-1ist and key to the British species is presented. Maps of the distribution of the British species within Britain and in the Northern Hemisphere are given, full details of all the British records being included in an appendix. Notes on the typification, characteristics, and idenities of non-British taxa studied in the course of my work are given separately. Reprints of some of my papers which are relevant to this thesis are also enclosed