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REPRODUCTIVE ORGANS 279
as "
hypophloeodal." But in some families, such as Roccellaceae, the thallus
attains a very advanced form and a very high production of acids.
The conception of Graphidineae as a whole is puzzling, but one or other
characteristic has brought the various members within the series. It is in
this respect an epitome of the lichen class of which the different groups,
with all their various origins and affinities, yet form a distinct and well-defined
section of the vegetable kingdom.
d. CYCLOCARPINEAE. This is by far the largest series of lichens. The
genera are associated with algae belonging both to the Myxophyceae and
the Chlorophyceae, and from the many different combinations are produced
great variations in the form of the vegetative body. The fruit is an emergent,
round or roundish disc or open apothecium in all the members of the series
except Pertusariaceae, where it is partially immersed in thalline " warts."
In its most primitive form, described as "biatorine" or "lecideine," it may
be soft and waxy {Biatorci) or hard and carbonaceous (Lecidea), in the latter
the paraphyses being mostly coloured at the tips ;
these are either simple or
but sparingly branched, so that the epithecium is a comparatively slight
structure. The outer sterile tissue forms a protective wall or "proper margin"
which may be entirely pushed aside, but generally persists as a distinct rim
round the disc.
A great advance within the series arose when the gonidial elements of
the thallus took part in fruit-formation. In that case not only is the
hymenium generally subtended by a layer of algae, but thalline tissue containing
algae grows up around the fruit, and forms a second wall or thalline
margin. This type of apothecium, termed " lecanorine," is thus intimately
associated with the assimilating tissue and food supply, and it gains in
capacity of ascus renewal and of long duration. This development from
non-marginate to marginate ascomata is necessarily an accompaniment of
symbiosis.
There is no doubt that the Cyclocarpineae derive from some simple
form or forms of Discomycete in the Patellariaceae. The relationship
between that family and the lower Lecideae is very close. Rehm 1 finds the
direct ancestors of Lecidea itself in the fungus genus, Patinella, in which the
apothecia are truly lecideine in character open, flat and slightly margined,
the hypothecium nearly always dark-coloured and the paraphyses branched,
septate, clavate and coloured at the tips, forming a dark epithecium. More
definitely still he describes Patinella atroviridis, a new species he discovered,
as in all respects a Lecidea, but without gonidia.
In the crustaceous Lecideaceae, a number of genera have been delimited
on spore characters colourless or brown, and simple or variously septate.
In Patellariaceae as described by Rehm are included a number of fungus
1 Rehm 1890.