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.
The paraphyses are commonly distinct in young apothecia, but in mature apothecia they are usually more or less gelatinized and coherent. In some of the species, they become so gelatinized that they form a homogeneous mass about the asci, in which the individual paraphyses are no longer discernible. When distinct, the paraphyses are sometimes branched, most commonly toward their apices ([Fig. 1] and [12]).
There is great diversity with respect to spore development, the whole range of spore structure, from minute, simple, hyaline spores to those which are large, brown, and muriform being found within the family (Figs. [3], [4], [5], [6], [7], [8], [9], and [13]). This condition makes it appear quite possible that the family may be polygenetic.
The genus, Biatorella, contains non-lichen forms and is probably as a whole more closely related to the Patellariaceae than to the Lecidiaceae. However, our two species, both of which are lichens, are herein admitted to the latter family. Through one or more species with larger spores than are usually found in this genus, Biatorella approaches Lecidea. Starting with Lecidea, we have a natural series in spore development with intermediate conditions difficult to place. The series runs thus: Lecidea with simple hyaline spores ([Fig. 3]); Biatorina with two-celled, hyaline spores ([Fig. 4]); Bilimbia with several-celled, hyaline spores, not much narrowed ([Fig. 5]); and Bacidia with several-celled, hyaline, acicular spores ([Fig. 6]). Buellia and Rhizocarpon are aberrant genera, brown-spored, and closely related among themselves (Figs. [8], [9], and [13]). Through Buellia, the two genera are related to Rinodina of the Physciaceae. The two aberrant genera are like other members of the Lecideaceae with respect to thallus development and general apothecial characters, the aberrancy being with respect to the spores, on which account the two genera are placed in another family, the Buelliaceae, by some workers, perhaps with sufficient reason.
The algal host is Pleurococcus-like ([Fig. 2], c) in nearly all species of the Lecideaceae; but the host cells are so hypertrophied and distorted that their generic rank is often difficult to ascertain, except by cultivation outside of the lichen thallus. The algal-host cells are few in number in some of the species and are sometimes absent during a portion of the life history of the lichen. The host is usually found throughout the superficial portions of the thallus, except near the upper surface, from which portion the algae are usually absent, except in a dead or dying condition, difficult to detect.
The writer has collected the Lecideaceae, with other fungi, in Butler County for fifteen years, and has worked for the Ohio Biological Survey in Preble, Warren, Highland, Fairfield, Adams, Hocking, and Lake counties. Besides these collections made by the writer, a few specimens were examined from Champaign, Hamilton, Wayne, Morgan, Madison, Muskingum, Franklin, Vinton, and Summit counties. Of the 37 species treated in this paper, 24 had not been reported from Ohio previously.