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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

[Pg 334]

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 ofthe Lecideaceae in an early paper of the series would show what slightchanges are needed in treating lichens as we treat other ascomycetes. Itis hoped that this paper has accomplished this in phraseologyintelligible to those acquainted with the present-day language ofsystematic mycology.

The Lecideaceae form a well-defined family of lichens, the affinitiesof which seem plainly marked. In apothecial structure, and so far asknown, in structure of the sexual reproductive areas, the family seemsto be closely related to the mainly non-lichen Patellariaceae and tosuch lichens as the Gyalectaceae, the Lecanactidaceae, theCollemaceae, the Baeomycetaceae, and the Cladoniaceae.

Following the commonly-accepted theory that the lichens have beenevolved from non-algicolous fungi, the origin of the Lecideaceae andrelated lichens from Patellaria-like ancestors is a reasonablesupposition, though the relative rank of the various related familiesnamed in the last paragraph is not easy to decide. Within theLecideaceae, the line of evolution seems to have been in the directionof a well-developed exciple and from simpler to more complex spores.With the advance in these two directions has gone a slightly increaseddevelopment of the thallus.

In structure, the thallus is crustose, and the thalli vary frominconspicuous, evanescent conditions to those which are conspicuous andsometimes even subsquamulous. Rarely the thallus extends upward as aveil which surrounds the apothecia laterally and suggests how thethalloid exciple of higher families probably arose. As usual in crustoseforms, the thalli are composed of hyphae which are densely disposedtoward the upper, exposed surface and more loosely disposed toward thelower surface (Fig. 2).

The apothecial evolution passes from forms with weak, light-coloredexciples and soft texture (Fig. 10) to those with strong, dark exciples,which are firm in texture (Fig. 11). The superficial apothecialcharacters are so much alike in many of the species that one cannotalways feel certain even of the genus of unfamiliar forms until he hasstudied them microscopically.[Pg 335]

The paraphyses are commonly distinct in young apothecia, but in matureapothecia they are usually more or less gelatinized and coherent. Insome of the species, they become so gelatinized that they form ahomogeneous mass about the asci, in which the individual paraphyses areno longer discernible. When distinct, the paraphyses are sometimesbranched, most commonly toward their apices (Fig. 1 and 12).