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PERICHAENA PEDATA G. LISTER.
A MYCETOZOON NEW TO ESSEX.
By G. LISTER, F.L.S., and J. ROSS.
(With One Plate.)
THIS species was found by J. Ross while he was searching
for mycetozoa among dead leaves, between the Warren
estate and the Loughton road, in Epping Forest, in mid-
December, 1938, and again in fair abundance in the following
month after a heavy fall of snow had melted. The minute orange
or reddish-brown sporangia are scattered over much decayed
wych-elm leaves, and are solitary or occasionally in clusters of
two or three; they vary from 0.1 to 0.9 mm. in diameter; they
have black stalks, which usually equal the sporangia in height;
exceptionally a sessile sporangium occurs. The sporangium
walls are slightly glossy and consist of a single membranous layer,
somewhat thickened with refuse matter on the outer surface,
and more or less papillose on the inner surface; they break up
at length into many polygonal areolae, when the mass of yellow
spores and capillitium is exposed.
Perichaena pedata was first found by A. and G. Lister in
South Devon near Lyme Regis in April, 1902. It was at first
regarded as a stalked variety of P. vermicularis (Schwein.) Rost.
(Journ. Bot. May, 1904, p. 139, pl. 459, figs. 3, 4), and later as a
stalked form of P. chrysosperma (Currey) Lister ("Mycetozoa," ed.
3, 244). Repeated gatherings in which the distinctive features are
retained prove that P. pedata is worthy of specific rank.1 It
has now been recorded from Devon, Worcestershire, Kent,
Essex, Suffolk, from near Aberdeen, and also from Fairmount
Park, Philadelphia, U.S.A.
P. pedata is nearly allied to P. tessellata G. Lister (Journ.
Bot. December, 1934, p. 297, pl. 598, fig. 2), a rare species known
only from gatherings made by His Majesty the Emperor of
Japan at Nasu in the island of Nippon, in September, 1930.
It is distinguished from P. pedata by the minute spherical
sporangia being sessile and having walls consisting of two
layers; the outer layer is purplish-black and thickened and
1 For description see Journal of Botany, Nov., 1937, p. 326.