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Diderma simplex (Schroet.) Lister
A Mycetozoan new to Epping Forest
BY JOSEPH BOSS
I found this species in some quantity in the woodland close to Chingford in
October, 1956. It was not included in the list of species found in
Epping Forest, originally compiled by Miss Gulielma Lister and maintained by
me. This is the 108th species of Mycetozoa to be noted in Epping Forest. It
may be of interest to members to learn that the last addition to the list was
Trichia floriformis G. Lister which I found in October, 1946, exactly ten years
ago.
The genus Diderma is distinguished, as its name suggests, by the sporangia
usually having walls composed of two layers. The walls of the sporangia con-
tain deposits of lime in granules. The sporangia of this genus may be stalked
or sessile or may be in the form of plasodiocarps. The threads of the capillitium
are without lime-knots and may be either simple or branched. The spores are
violet-brown or purplish-grey.
Diderma simplex differs from the usual characters of the genus in having but
a single wall to the sporangia, which are usually either reddish clay-coloured,
brownish-buff or rarely yellow. The gatherings I made are buff. The sporangia
of Diderma simplex are somewhat crowded, sessile and sub-globose, hemis-
pherical and sometimes depressed. Occasionally they form short curved
plasmodiocarps. The sporangium wall is single, membranous and contains
abundant deposits of coloured lime-granules. The capillitium consists of slender
colourless or dark branching threads, often with expansions at the base con-
taining lime-granules. The spores are brownish-violet. The species resembles
in some ways various species of the genus Trichia but these are to be found
developing on wood, or if found elsewhere have travelled thence from the wood
in which they developed. Diderma simplex has been recorded on moss, heather
(on moorland) and on dead leaves. In the Forest I found it on dead leaves of
holly and oak and on two or three twigs. Records of this species are given for
Sussex, Surrey, Norfolk (where Mr. H. J. Howard found it on leaves under
brambles on August 9th, 1917), Yorkshire, North Wales, Aberdeenshire and
now from Essex. Abroad it has been recorded from France, Germany,
Moldavia, New Jersey, Pennsylvania, North Carolina and eight other states of
U.S.A., Ontario (Canada), and South Chile.
Although this communication appears under my name it has been mainly
prepared by Mr. B. T. Ward who also mounted specimens presented to the
collections in the British Museum; the Museum at the Queen Elizabeth
Lodge, Chingford; and the Passmore Edwards Museum, Stratford. I have
also to thank Mr. Ward for submitting a specimen to Mr. H. J. Howard of
Norwich for confirmation, for comparing a specimen with those in the South
Kensington collections and for arranging for the exhibit of a specimen at the
Club's November, 1956 meeting.