Produced by Charlene Taylor, La Monte H.P. Yarroll, Taavi Kalju and the Online Distributed Proofreading Team at http://www.pgdp.net Volume II, No. 6 Bulletin No. 10 OHIO BIOLOGICAL SURVEY THE ASCOMYCETES OF OHIO IV THE LECIDEACEAE By BRUCE FINK THE ASCOMYCETES OF OHIO V THE PELTIGERACEAE By LEAFY J. CORRINGTON Published by THE OHIO STATE UNIVERSITY COLUMBUS, 1921 THE ASCOMYCETES OF OHIO IV[A] The Lecideaceae. BRUCE FINK. GENERAL CONSIDERATIONS It was stated in the second paper of this series that the disposition of the _Lecideaceae_ in an early paper of the series would show what slight changes are needed in treating lichens as we treat other ascomycetes. It is hoped that this paper has accomplished this in phraseology intelligible to those acquainted with the present-day language of systematic mycology. The _Lecideaceae_ form a well-defined family of lichens, the affinities of which seem plainly marked. In apothecial structure, and so far as known, in structure of the sexual reproductive areas, the family seems to be closely related to the mainly non-lichen _Patellariaceae_ and to such lichens as the _Gyalectaceae_, the _Lecanactidaceae_, the _Collemaceae_, the _Baeomycetaceae_, and the _Cladoniaceae_. Following the commonly-accepted theory that the lichens have been evolved from non-algicolous fungi, the origin of the _Lecideaceae_ and related lichens from _Patellaria_-like ancestors is a reasonable supposition, though the relative rank of the various related families named in the last paragraph is not easy to decide. Within the _Lecideaceae_, the line of evolution seems to have been in the direction of a well-developed exciple and from simpler to more complex spores. With the advance in these two directions has gone a slightly increased development of the thallus. In structure, the thallus is crustose, and the thalli vary from inconspicuous, evanescent conditions to those which are conspicuous and sometimes even subsquamulous. Rarely the thallus extends upward as a veil which surrounds the apothecia laterally and suggests how the thalloid exciple of higher families probably arose. As usual in crustose forms, the thalli are composed of hyphae which are densely disposed toward the upper, exposed surface and more loosely disposed toward the lower surface (Fig. 2). The apothecial evolution passes from forms with weak, light-colored exciples and soft texture (Fig. 10) to those with strong, dark exciples, which are firm in texture (Fig. 11). The superficial apothecial characters are so much alike in many of the species that one cannot always feel certain even of the genus of unfamiliar forms until he has studied them microscopically.