One of the common features of lignicolous fungi is the fact that they lack a distinct stem or if one is present it is attached to one side of the cap, i.e. lateral. However, in the past the correlation of the habitat with lack of stem has induced mycologists to define a single family to include all these forms. After studying the anatomy and microscopic characters this grouping has been found to be entirely artificial and simply reflects how the morphology is tied up intimately with the ecology of a species. In this one family members of the genera _Panus_, _Panellus_, _Lentinus_, _Lentinellus_, _Crepidotus_, _Pleurotellus_, and _Pleurotus_ have all been grouped together, but some of the genera are more related to the polypores referred to later (p. 135); many of those with brown spores are better placed with _Cortinarius_ and some of those with white or cream-coloured spores are better placed close to _Mycena_ and _Tricholoma_. This leaves as a residue the genus _Pleurotus_, a genus which although rather heterogeneous contains one familiar member, i.e. the common Oyster mushroom, _Pleurotus ostreatus_. ~Pleurotus ostreatus~ (Fries) Kummer Oyster mushroom Grows up to 150 mm across. Cap: flattened, shell-shaped, smooth or slightly cracked, deep bluish grey, gradually becoming brownish with age and finally dark buff. Stem: absent or very short, passing gradually into one side of the cap. Gills: white flushing dirty yellow with age, rather distant and deeply decurrent. Flesh: white, soft and with very pleasant smell. Spore-print: pale lilac. Spores: long, hyaline, oblong under the microscope and 10-11 × 4 µm in size. Marginal and facial cystidia: absent. _Habitat_ & _Distribution_: Common, clustered in tiers on stumps, trunks, posts, etc. _General Information_: This fungus is not infrequent on old telephone-poles and forms white sheets of mycelium immediately under the bark of fallen trees. Although frequent in autumn it may be found throughout the year and is easily recognised by its size and bracket-like, shell-shaped caps. It surprisingly has a pale lilac spore-print and not as might be expected a white spore-print. In the var. _columbinus_ Quélet the young caps are a beautiful peacock-blue; this variety frequently grows on poplars. _Illustrations_: F 125²; Hvass 109; LH 107; NB 125²; WD 31¹. [Illustration: Plate 17. Wood-inhabiting, fleshy but leathery fungi: Spores whitish or brownish and borne on gills--‘Pleurotaceae’] ~Panus torulosus~ (Fries) Fries is a tough, funnel-shaped, yellowish cinnamon fungus with oblong-ellipsoid, small, hyaline spores measuring 5-6 × 3 µm and changing yellowish not bluish grey in iodine solutions. ~Panellus stipticus~ (Fries) Karsten forms tiers of pale cinnamon-brown, more or less kidney-shaped, scurfy caps on old wood and has egg-shaped, hyaline, small spores measuring 4 × 2-3 µm which become bluish grey in iodine solutions.