Pileus up to 18 x 8 mm when still closed, up to 32 mm when expanded, first whitish, soon grey with cream or pale ochre centre below a pure white, hairy-floccose veil that splits up in hairy flocks and, as well as the pileus, very soon dissapears. Lamellae, L = c. 35--45, l = 0--3, crowded, free, at first white, soon grey to black. Stipe 60--150 x 1--3 mm, pure white, at first densely covered with bristly, hairy-floccose veil, hollow, very fragile and soon laying down; base up to 4 mm wide, clavate.
  Spores [200, 10, 5] 9.6-13.8 x 6.3-8.3 µm; Q = 1.35-2.05, av. Q = 1.55-1.80; av. L = 10.7-12.5 µm, av. B = 6.7-7.9 µm, ellipsoid or ovoid, less frequently oblong, medium-brown, sometimes very dark red-brown, with rounded base and apex, and c. 2 µm wide, central germ pore. Basidia 21-37 x 8-11 µm, 4-spored, surrounded by 3-6 pseudoparaphyses. Pleurocystidia 50-100 x 25-45 µm, (sub)utriform, oblong, ellipsoid or subcylindrical. Cheilocystidia 40-95 x 22-40 µm, (sub)utriform, oblong, ellipsoid or subglobose. Pileipellis a cutis, made up of elongate, often short elements. Veil made up of 25-125 x 8-40 µm, hyphoid elements in chains. Wall of the stipe l30--240 µm thick. Clamp-connections present, c. 3-4 µm in diameter.

Habitat & distribution

  Rather common in short-mown lawns, solitary, seldom a few together. Known from Alphen aan den Rijn and Zoetermeer (the Netherlands), from several lawns.

Remarks

  The very fragile basidiocarps, the habitat, the usually somewhat less slender spores (often slightly wider than broader) than in C. lagopus Fr.: Fr. var. lagopus, and the thin wall of the stipe are the main characters by which to recognize Coprinus lagopus var. vacillans. It is difficult to collect young basidiocarps in the field by reason of the very rapid developing and wilting of the pileus. Although the pure (silvery) white stipe is very fragile, it does not disappear as quickly as the pileus and stipes can be found, often in great number, lying on the ground with a black, snotty remnant of the pileus at their extremities. The stipe bends down as soon as it starts to grow, even while the pileus is still closed. Microscopically the wall of the stipe is often thinner than 200 ?m, though sometimes reaching 240 ?m, whereas in C. lagopus var. lagopus it usually lies between 200 and 450 ?m. Nonetheless most microscopical features are rather similar to C. lagopus so we prefer at the moment to describe it as a new variety rather than to erect a new species.