38
THE MYCETOZOA:
yellow species has been recorded from Essex. It was found
by Mr. J. Ross on holly leaves, August 1915, in the forest near
Chingford.
Leocarpus fragilis (Dicks.) Rost.—Abundant in autumn
on sticks, bracken, heather, etc. The yellow plasmodium often
creeps far from its feeding grounds to find a suitable place in
which to fructify and scatter the spores.
Diderma effusum (Schwein) Morg.—Not uncommon on
dead leaves, especially those of holly, from June to September.
D. radiatum (L.) Lister var. umbilicatum Meylan.—
The type of this species in the Linnean Herbarium has brown
sporangia dehiscing by stellate lobes, a form far less frequent
in Britain than one with grey sporangia which open irregularly ;
the latter form was described by Persoon as Diderma umbilicatum;
although growths showing intermediate characters are not
rare, it is well to recognise the form with grey sporangia as
representing a distinct variety ; I follow M. Ch. Meylan in
adopting the varietal name umbilicatum.14 This variety
is not unfrequent in autumn and mild winters on dead bramble
leaves, stems and twigs ; the greyish or white sporangia are
usually grouped in small scattered clusters.
D. floriforme Pers.—Probably not uncommon on old stumps
from June to December.
Diachaea leucopoda (Bull.) Rost.—Not uncommon from
August to November on heaps of dead leaves and twigs ; some-
times the cylindrical white-stalked sporangia occur in great
profusion, developing from large plasmodia.
Didymium difforme (Pers.) Duby.—Common on heaps of
decaying leaves and dead herbaceous plants, almost
throughout the year.
D. Clavus (Alb. & Schw.) Rabenh.—Abundant on dead
leaves in summer and autumn ; also occurring on the trunks
of living trees among moss.
D. complanatum Rost.—Apparently rare, but possibly
overlooked from being mistaken for a plasmodiocarp form
of D. squamulosum, which it outwardly resembles. Found in
Wanstead Park in summer on dead leaves, developing from
lemon-yellow plasmodium.
14 See Meylan, " Myxomycetes du Jura," in L'Annuaire du Conservatoire et du Jardin
botanique de Geneve. 1913. p. 312.