_General Information_: This fungus is often buried to half-way in the sand of slacks near dwarf willows (_Salix_ spp.). Three other species of _Inocybe_ grow in dune-slacks _I. halophila_ Heim, _I. serotina_ Peck and _I. devoniensis_ P. D. Orton, but all differ in their spores being smooth and elongate-cylindric. _Astrosporina_, a name referring to the shape of the spore, has been considered a genus of agarics in its own right and to this group _I. dunensis_ would belong. However, as the members show the same range of characters as those species with the smooth spores it seems unnecessary to split _Inocybe_ into two. The cystidia in many species are unusual, being crested with a bundle of crystals which have been reported as being calcium oxalate, although even the simplest school-laboratory tests have been rarely applied to them (see p. 84). [Illustration: Plate 79. Sand-dune fungi] ~Psathyrella ammophila~ (Durieu & Léville) P. D. Orton Sand-dune brittle-cap _Cap_: width 20-40 mm. _Stem_: width 4-8 mm; length 40-80 mm. _Description_: Plate 79. Cap: semiglobate to convex, pale dingy clay-colour or dark tan to dirty brownish, non-striate, rather fleshy and usually sand covered. Stem: deeply rooting in sand and club-shaped towards the base, similarly coloured to the cap except for the whitish apex. Gills: adnate, subfuscous or dark dirt-brown. Flesh: dirty buff and with no distinct smell. Spore-print: pale snuff-brown with purplish flush. Spores: long, ovoid, yellowish-grey brown under the microscope with a distinct germ-pore and 10-12 × 7 µm in size. Marginal cystidia: balloon-shaped, obtuse or somewhat bottle-shaped and hyaline. Facial cystidia: sparse, similar to the marginal cystidia, voluminous. _General Information_: This is a very distinct fungus found amongst stems of Marram grass in sand-dune systems. At first sight it appears as if it is growing in the bare sand, but by careful excavation it usually is found attached to pieces of Marram grass, indeed the hyphae enter the roots of the grass, but apparently do not kill them. This fungus was first described in the genus _Psilocybe_ (see p. 114) because of its brownish purple spore-print, but the cap-surface is composed of rounded cells and so is related to all the other species of _Psathyrella_. _Psathyrella flexispora_ Wallace & P. D. Orton grows in similar habitats amongst _Ammophila_ and other seashore grasses. It is easily recognised by the chocolate, umber or date-brown cap and the peculiar shaped spores, which look as if they have been slightly twisted during their development.