56 THE ESSEX NATURALIST
of leaves. Except that Mr. W. D. Graddon once obtained it
farther along the same ridge, the species has not been reported
from any other locality. I think that it is more plentiful in the
Warren plantation than it was a few years ago. As it matures
at some depth in the leaf beds it would appear that the spores
have but restricted opportunities of dispersion by air currents,
and possibly my own disturbance of the leaves when searching
in the plantation may have helped the distribution of the spores
in the area. It has been found a few times in the belt of wood-
land south of the Forest Superintendent's residence, where it
occurred in thin beds of leaves amongst brambles. Greenish
plasmodium from which I have twice reared the sporangia is
not infrequent in the leaf beds of the Warren plantation.
Didymium laxifila frequently has confluent sporangia sup-
ported by two or three reddish, reddish-yellow or yellow mem-
branous stalks. At times the sporangia appear to be sessile,
as being deeply umbilicate they overhang the short stalks and
prevent them being easily seen in the field. The sporangia are
situated on a yellowish hypothallus which frequently separates
from the substratum so that the stalks, however short, then
become evident. The nearest approach to a sessile form I have
seen was one in which the stalk was little developed on one side
though plain on the other. Features of the species when
examined microscopically are the dense coating of snow-white
stellate lime crystals on the sporangium wall and the lax network
of stout capillitium threads which, in coalescing forms may be
confluent above two or three short stalks. The species has a
partiality for the edges of leaves and for the edges of holes made
in leaves by insects.
Another species which always receives particular attention is
Colloderma oculatum, to which Miss Lister introduced me
thirty-four years ago. In 1933 I reported (see Essex Naturalist,
vol. xxiv, p. 62) that the species had been occurring more or less
regularly on an old oak log for twenty years; in 1946 it again
developed on this log and on a nearby log where it had been
found many years ago. The log on which the species has
matured most successfully was rolled over in 1932; it was
turned back to its original position and a few months later
Colloderma reappeared. Some years later the log was again
rolled over and has not been replaced, yet last autumn Collo-
derma developed on the side which, now uppermost, was under-
neath when the log was first noticed. My best station for
Colloderma nowadays is an old beech log on which grow grass,
lichens, mosses and liverworts; specimens were collected there
in December, for it is hardy and has a protective gelatinous
envelope when it emerges.