Spores: long, yellow-brown under the microscope, ellipsoid with a very distinct germ-pore about 13 × 8 µm in size (11-15 × 6-9 µm).
Facial cystidia: rare, balloon-shaped.
Marginal cystidia: swollen, flask-shaped with a variable, elongate neck.
General Information: This fungus is common on horse droppings or other manures, but it may also be found amongst grass in pastures and in sand-dunes, and gardens on piles of rotting grass stems or straw. It is easily recognised by the colour and rapid expansion of the cap and the sudden collapse of the whole fruit-body. ‘Vitellinus’ means yolk of an egg and refers to the persistently bright yellow cap-centre, so obvious even when the fruit-body collapses. This collapsing is not one of autodigestion as described for members of the genus Coprinus. It is variable both in size and habitat, and I even have records of the fungus growing within herbaceous stems.
Illustrations: LH 153; WD 806.
Stropharia semiglobata (Fries) Quélet Dung-roundhead
Cap: width 10-35 mm. Stem: width 4-7 mm; length 25-50 mm.
Description:
Cap: hemispherical or slightly umbonate, sometimes flattened and hardly expanding even with age, very viscid, smooth, pale yellow-ochre or yellowish tan.
Stem: slender, straight, white then yellowish, smooth, viscid, but then dry and shiny below an imperfectly formed, thin ring.