THE ASCOMYCETES OF OHIO IV* 
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-\\ke 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 evolu¬ 
tion 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 tballus. 
In structure, the thallus is crustose, and the thalli vary from inconspic¬ 
uous, 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 Trom 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. 
•Contributions from the Botanical Laboratory of Miami University.—XVIII 
334 
