r 4 4 
HYMENOMYCETES 
and rounded behind, broad, somewhat crowded, whitish. 
S. eccentric, 2-3 in.; about 1 in. thick, white. Singly or in 
tufts on trunks of various trees, chiefly elm, in aut. and win. 
Not common: 
P. ostreatus ( ostrea , an oyster—from the colour of the 
pileus), “ The Oyster.” 
P. 3-6 in., imbricated, convex, with involute margin at 
first, then expanded and ascending, glabrous, moist, even 
(sometimes squamulose), dark when young, then brownish 
or bluish-grey. Often tinged with violet or lavender, usually 
becoming yellowish at maturity, shining and satiny when 
dry. G. decurrent, rather distant, broad, white; sometimes 
yellowish, never tinged pink. S. very short or absent, firm, 
swollen above, white and downy below. “ Caespitose. Smell 
strong. The stem is sometimes almost central. Distin¬ 
guished from all species, except P. corticatus (which is rare), 
by the gills anastomosing behind, and often forming an open 
network on the stem-like base. Known from P. corticatus 
by the absence of a ring on the stem” (Massee). Frequent 
on trunks of various trees in aut., win., and spr. Dr. 
Plowright observed it growing on the dried brain of a 
stranded whale. The var. euosmos is easily recognised by the 
lilac or purple tinge of the spore mass and the strong 
smell of tarragon. 
P. septicus ( septicus, putrifying—from its habitat, rotten 
wood). Plate XXXVI. 9. 
Entirely white. P. J in., downy, at first resupinate, with 
a minute downy stem, which disappears as the pileus 
becomes reflexed. G. radiating from the point of attach¬ 
ment of the stem, broad, rather distant. “ Small, but very 
variable in form. Superficially resembling Claudopus vavia- 
bilis, but the gills are persistently white, as are also the 
spores. Distinguished from the other small white species 
of Pleurotus by the thicker flesh of the pileus and more 
evident stem, and by the gills being at first uppermost, and 
