61
ON THE OCCURRENCE OF LICEA PUSILLA
(SCHRADER) IN ESSEX.
By G. LISTER, F.L.S.
(With One Plate.)
THIS minute representative of the Mycetozoa has recently
been recorded for the first time from Essex. During
the Club's Fungus Foray in the Loughton district of Epping
Forest on October nth, 1930, some slices of decayed wood,
clothed with a layer of gelatinous alga;, were cut from a fallen
oak log and brought indoors for observation. Such wood,
after being kept in a moist chamber for weeks, or even months,
has repeatedly proved to be a favourable habitat for Colloderma
oculatum. That species has not so far developed (November 12th)
but a crop of Arcyria pomiformis, and, later, of very slender-
stalked Comatricha nigra, soon appeared. About a week after
collection, on most of the slices of oak wood (cut from various
parts of the parent log) numerous very minute sporangia of
Licea pusilla were seen scattered over the algal layer. It is
characteristic of this species, as it is of the closely allied L.
minima Fries, that many small plasmodia keep developing
independently from the same wood, so that within an area of
a few square millimetres every stage may be seen from the
minute pin-heads of freshly emerging grey plasmodium to
immature pale olive and mature sessile black sporangia. During
the whole of the last month, up to mid-November, they have
continued to develop.
L. pusilla has usually been regarded as a more showy species
than L. minima, and is described as having sporangia measuring
from 0.6 to 1mm. diameter, but in the present cultivation they
are extremely inconspicuous and measure, mostly, only 0.1 to
0.3 mm. diameter, the largest yet formed being 0.7 by 0.4 mm.
Although in this genus no capillitium threads occur to aid
in the dispersion of the spores, the structure of the sporangium
is not merely a mass of spores enclosed by a uniform wall. At
an early stage of development the peridium is seen to be marked
with pale anastomosing bands which are free from the dark