The peculiar pointed cystidia found on the gill-edge and on the gill-face of _P. cervinus_ were thought by some early mycologists to stop mites and insect larvae from crawling up between the gills and damaging the developing spores. There is no evidence that this actually takes place in nature; the real purpose of these obscure structures is unknown and has been little studied. _Illustrations_: Hvass 127; LH 121; NB 135¹; WD 50². [Illustration: Plate 15. Fleshy fungi: Spores pinkish and borne on gills] ~Gymnopilus penetrans~ (Fries) Murrill _Cap_: width 20-50 mm. _Stem_: width 4-7 mm; length 20-50 mm. _Description_: Cap: convex then becoming flattened at maturity, dry, slightly scaly, golden tawny, or rusty yellow and when young with the remnants of a rapidly disappearing yellow cortina hanging from the margin. Stem: yellow above and red-brown or orange-tawny below and darkening on bruising; veil forming a delicate fibrillose zone in the upper part of the stem which is soon lost on excessive handling. Gills: adnate to slightly decurrent, thin and crowded, at first golden yellow, but soon spotted rust colour. Flesh: yellow and lacking distinctive smell. Spore-print: rich orange-tawny. Spores: medium-sized, ellipsoid, finely roughened and deep yellow brown under the microscope, less than 10 µm in length (7-8 × 5-4 µm). Marginal cystidia: hyaline, flask-shaped with long often slightly irregular neck. Facial cystidia: similar to the marginal cystidia, but often broader. _Habitat_ & _Distribution_: This fungus is found on sticks or twigs or chips of coniferous wood, particularly in plantations. _General Information_: Although it has only comparatively recently been recognised in Britain it is very wide-spread. It has been confused with, indeed described under, the name of the less-common fungus _Gymnopilus sapineus_ (Fries) Maire which also grows in conifer woods; it is easily distinguished, however, by its spotted gills. Both the fungi above can be found in books under the old name _Flammula_, from the bright colour of the caps of many of its constituent members, but _Flammula_ has been used for a genus of flowering plants also and this has precedence. _Illustrations_: F 29a; Hvass 152 not very good; LH 175 not very good; NB 109⁶. [Illustration: Plate 16. Fleshy fungi: Spores rust-brown and borne on gills] Notes on the artificial family group ‘_Pleurotaceae_’--the Oyster mushrooms