THEIR HABITATS GENERALLY.
15
Oerstedtii. If the timber is much decayed, it will often produce,
in summer time, sheets of the white fleecy sporophores of Cera-
tiomyxa.
On old fallen pine boughs, barked and green with algal
growth, we may look for the dark sporangia of Dianema cortica-
tum, and some of those small species of Comatricha that are
hard to see without a lens.
Pine and larch needles, unmixed with other leaves, do not
form a rich feeding ground, although one may sometimes find
under pine trees such large growths of Didymium melanospermum
as to form hoary patches on the brown carpet of needles.
Sawdust-Heaps formed from cutting up fir logs are often
prolific in Mycetozoa. I remember some old deep beds of saw-
dust near Forres that were gay with patches, many inches
across, of the yellow Fuligo septica and of young rosy Trichia
decipiens. Such a showy effect was produced that an attempt was
made to perpetuate the scene by means of colour photography.
Among other species which have been found in abundance
on such sawdust beds are Cribraria pyriformis and Dictydium
cancellatum.
Turning to woods formed of Deciduous Trees, one is almost
overwhelmed by the wealth of species such habitats afford.
Beeches usually stand on well-drained ground. Their living
trunks, however, overgrown with moss and lichen (as they
often are near the base), may prove a more favourable haunt
for Mycetozon than we yet realize. The first English gathering
of Diderma arboreum was made last winter by Dr. Adams, on
a mossy beech trunk in Cornwall ; and our only English record
for that inconspicuous little species, Orcadella operculata, was
made by Mr. W. H. Burrell on a living beech trunk in Norfolk.
On decaying beech logs many of our commoner wood-feeding
Mycetozoa abound, such as Physarum nutans, with its protean
varieties, the flat brown cakes of Dictydiaethalium, and the
crimson Arcyria denudata.
Oaks are favourable for Mycetozoa that feed both on dead
wood and dead leaves, and even their living trunks have afforded
a number of species. On lichen- and moss-grown oaks, standing
exposed to weather on the slopes of Hind Head, have been found
scattered sporangia of Enerthenema papillatum and small growths
of Arcyria pomiformis and Hemitrichia abietina. The two former