~A. arvensis~ Secretan the Horse-mushroom is also edible, but is much bigger (up to 180 mm), creamy white and bruises slightly yellowish on handling; it also has larger spores (7-10 × 5 µm), club-shaped cells on the gill-edge, gills commencing white and not pink, and the presence of a complex ring. ~A. xanthodermus~ Genevier the ‘Yellow-staining mushroom’ has even smaller spores than the field mushroom, i.e. 5-6 × 4 µm and a rather strong, unpleasant smell; if eaten many people subsequently suffer from stomach-pains and this shows that even amongst those fungi which the scientist would call true mushrooms, i.e. those fungi in the genus _Agaricus_, there are some poisonous members. Thus it is always necessary to have wide experience before one collects fungi for eating and until this is achieved all specimens should be discarded. _Illustrations_: Field mushroom--Hvass 163; LH 133; NB 31⁶; WD 71². Horse mushroom--Hvass 160; LH 135; WD 72¹. Yellow-staining mushroom--Hvass 159; WD 71³. [Illustration: Plate 31. Fleshy fungi: Spores purple-brown and borne on gills] ~Calocybe gambosum~ (Fries) Singer. St George’s mushroom _Cap_: width 70-100 mm. _Stem_: width 15-25 mm; length 50-70 mm. _Description_: Cap: creamy white, ivory or light buff, slightly darker at the centre with age, fleshy, rounded and with wavy margin, finally expanding to become plane-convex; the margin is incurved and slightly downy at first. Stem: firm, rather thick, white at the top, creamy or buff below and slightly downy when fresh. Gills: sinuate to adnexed with a slight decurrent tooth, white to pale buff. Flesh: with a very strong smell of meal, white and thick. Spore-print: white. Spores: small, ellipsoid, smooth, hyaline under the microscope, 5-6 × 3-4 µm and not becoming blue-grey with solutions containing iodine. Marginal and facial cystidia: absent. _Habitat_ & _Distribution_: Found amongst grass in base rich pastures, often in fairly large rings from April to June and on golf-courses particularly those near the sea. _General Information_: The common name refers to the early appearance of this agaric; St George’s Day is April 23rd, and this mushroom is found about this time in favourable years, its fruiting often extending into early June, particularly if the fruiting is retarded by a cold and wet spring. It is easily recognised by the pale colour of the cap, strong mealy smell, but particularly by its appearance in spring. In each new year it is probably the first of the larger agarics to appear. This species will be found in most books under the genus _Tricholoma_, but differs from typical members of this group in the anatomy and chemistry of the gill-tissues.