write more specially of reproduction.

ASCOMYCETES.--Passing now to the _Ascomycetes_, which are especially
rich in genera and species, we must first, and but superficially,
allude to _Tuberacei_, an order of sporidiiferous fungi of subterranean
habit, and rather peculiar structure.[u] In this order an external
stratum of cells forms a kind of perithecium, which is more or less
developed in different genera. This encloses the hymenium, which is
sinuous, contorted, and twisted, often forming lacunae. The hymenium in
some genera consists of elongated, nearly cylindrical asci, enclosing a
definite number of sporidia; in the true truffles and their
immediate allies, the asci are broad sacs, containing very large and
beautiful, often coloured, sporidia. These latter have either a
smooth, warted, spinulose, or lacunose epispore, and, as will be seen
from the figures in Tulasne's Monograph,[v] or those in the last
volume of Corda's great work,[w] are attractive microscopical objects.
In some cases, it is not difficult to detect paraphyses, but in
others they would seem to be entirely absent. A comparatively large
number have been discovered and recorded in Great Britain,[x] but of
those none are more suitable for study of general structure than the
ordinary truffle of the markets.

The structure of the remaining Ascomycetes can be studied under two
groups, _i.e._, the fleshy Ascomycetes, or, as they have been termed,
the Discomycetes, and the hard, or carbonaceous Ascomycetes,
sometimes called the Pyrenomycetes. Neither of these names gives an
accurate idea of the distinctions between the two groups, in the
former of which the discoid form is not universal, and the latter
contains somewhat fleshy forms. But in the Discomycetes the
hymenium soon becomes more or less exposed, and in the latter it is
enclosed in a perithecium. The Discomycetes are of two kinds, the
pileate and the cup-shaped. Of the pileate such a genus as _Gyromitra_
or _Helvella_ is, in a certain sense, analogous to the Agarics
amongst _Hymenomycetes_, with a superior instead of an inferior
hymenium, and enclosed, not naked, spores. Again, _Geoglossum_ is
somewhat analogous to _Clavaria_. Amongst the cup-shaped, _Peziza_
is an Ascomycetous _Cyphella_. But these are perhaps more fanciful
than real analogies.

Recently Boudier has examined one group of the cup-shaped Discomycetes,
the _Ascobolei_, and, by making a somewhat free use of his Memoir,[y] we
may a