Gills: adnate, almost triangular in shape, crowded, dark brown to purplish black, but with ochraceous areas at maturity.
Flesh: pale ochre.
Spore-print: purplish brown.
Spores: very long, dark brown under the microscope, smooth, ellipsoid with large germ-pore and about 18 × 10 µm in size (17-20 × 9-10 µm).
Facial cystidia: spindle-shaped, thin-walled and filled with amorphous contents which become yellow in solutions containing ammonia.
Marginal cystidia: spindle-shaped or flask-shaped, numerous, thin-walled and typically yellowing as above.
General Information: ‘Semiglobata’ means hemispherical and refers to the shape of the cap of S. semiglobata; it is a very variable fungus in both size of the cap and the prominence of the ring. The Dung-roundhead grows only on dung which is acidic in its soil status, whilst Panaeolus semiovatus (Fries) Lundell next described ([p. 210]) grows on slightly to distinctly base-rich dung. This may explain why in Britain the Dung-roundhead is the commoner of the two species. However, P. semiovatus was formerly placed in the genus Stropharia because of its blackish spores and distinct ring. The spores of Stropharia in the mass are violaceous black whilst those of P. semiovatus are brownish black. Under the microscope they are also differently coloured and have different chemical compositions as their reaction with dilute solutions of ammonia shows; the spores of the first species turn purplish olive in ammonia and those of the second species become very dark brown.
Illustrations: F 33b; Hvass 171; LH 153; NB 315; WD 753.
Plate 70. Dung-fungi
