THEIR HABITATS GENERALLY. 17
Birch and Willow.—On the soft decaying wood of these
trees, the dull red cushions of Tubifera ferruginosa may often
be found.
Ash.—On old ash timber, many Mycetozoa occur. In a
wooded valley near the sea at Lyme Regis, fallen ash boughs
are the favoured haunt of the rare Dianema depressum. This
species passes through a variety of colour changes as it matures ;
emerging from the wood in white or rosy plasmodium, it soon
forms into bright violet-coloured sporangia ; these eventually
assume an inconspicuous drab colour, and harmonize exactly
with the surrounding bark. If the sporangia were insects liable
to be eaten by birds, one might exclaim " What an excellent
example we have here of protective resemblance ! " Yet who
would venture to suggest that the dull hue of the mature
Dianema protects it from foes—slugs and woodlice, creatures
which, if attracted by bright colours, might have been par-
ticularly tempted by the rosy and violet phases of the same
sporangia in their younger, more juicy, and more palatable
condition. On living ask trunks and hidden amongst liver-
worts, Mr. N. G. Hadden found last winter, in Somerset, the
small buff sporangia of Hemitrichia minor, a species recorded
before only from Aberdeenshire and Japan.
Elm logs often produce large growths of Badhamia panicea
and, more rarely, of B. macrocarpa ; the plasmodium feeds on
the decaying inner bast and creeps to the surface of the bark
to form sporangia. The large pale aethalia of Lycogala flavo-
fuscum have repeatedly been found on dead wood inside the
hollow trunks of living elms by Mr. Charles Crouch, in Bedford-
shire. Mr, Crouch writes :—" I do not think the species is as
uncommon as supposed, but it wants looking for ; my finding
the last gathering was due to the blizzard of 1916, which
removed half the elm and exposed its inside ; another specimen
was found on an elm branch brought down by the same blizzard ;
a third I should not have found if a bird or something had not
tumbled it to the bottom of the tree."
Poplar.—On logs of poplar only has Badhamia populina
been found hitherto in Britain : in the United States it has been
obtained on both poplar and Box-Elder (Acer Negundo). Peri-
chaena corticalis occurs so frequently on dead poplars that
among the many specific names it has received is that of