Apothecia developing within leaf tomentum on undersides of living leaves of Olearia species (Asteraceae). Apothecia 0.1-0.15 mm diam., 0.2 mm high, black with numerous stiff, black setae, urn-shaped, tapering suddenly to a short, stipe-like base. Setae near top of apothecium extending outwards across top of leaf tomentum.

Ectal excipulum 2-layered. Inner layer 6-10 µm wide, in vertical section comprising 2 or 3 rows of brick-shaped cells 4.5-6 µm diam., with thin, brown walls. Outer layer patchy in development, comprising a single layer of cylindric cells 2.5-3 µm diam., with pale brown, irregularly encrusted walls, and with setae arising from these cells. Setae mostly near top of apothecium, 60-80 x 5-6.5 µm, often distinctively sickle-shaped, with very dark, thick walls, probably 0-septate. Seta-like or hair-like elements at sides and near base of apothecium, 12-20 x 2-3 µm, irregularly cylindric, with brown, slightly thickened walls, usually 2 or 3-septate. Medullary excipulum poorly developed, comprising 2 or 3 rows of hyaline, narrow-cylindric cells.

Paraphyses 2-2.5 µm diam., undifferentiated to slightly swollen near apex, about same length as the asci. Asci 55-70 x 6.5-7.5 µm, cylindric, tapering to slightly truncate apex, wall thickened at apex, non-amyloid, 8-spored. Ascospores 6.5-8 x 3-4 µm, broadly rounded at both ends, subclavate, slightly wider in upper half, hyaline, 0-septate.

Cultures approximately 50 mm diam. after 4 weeks. On OA with low, dense, felted, pale pinkish-grey mycelium; yellowish in reverse. On MEA with dense, cottony, white to pale grey mycelium; grey brown in reverse. Cultures remained sterile.

NOTES: Together with the unusual host substrate, ascospore size and shape differentiate C. falcata from the species treated by Nannfeldt (1985). Although most of these were also found on Asteraceae, all developed on dead leaf and stem tissue rather than the tomentum of living leaves. The asci of P. falcata appear to mature and discharge their spores while the leaves of the host plant are still alive, since all apothecia examined from fallen leaves were over-mature.

Several other species of Leotiales are associated with the leaf tomentum of Asteraceae in New Zealand. Johnston (1989) described three Crocicreas species and recorded C. epitephrum (Berk.) S.E. Carp., first described from Australia, from the leaf tomentum of various species. Another Australian species, Lachnum willisii (G.W. Beaton) Spooner, described from the leaf tomentum of Celmisia asteliifolia from Australia, also occurs on the tomentum of living leaves of Celmisia in New Zealand (MID CANTERBURY: Craigieburn Forest Park, near skifield, on Celmisia discolor, P.R. Johnston & E.H.C. McKenzie, 24 Feb 1988 (PDD 48634); Craigieburn Forest Park, near skifield, on Celmisia angustifolia, P.R. Johnston & E.H.C. McKenzie, 24 Feb 1988 (PDD 48458). NORTH CANTERBURY: Arthurs Pass National Park, Nature Trail near Temple Basin, on Celmisia discolor var. intermedia, P.R. Johnston & E.H.C. McKenzie, 25 Feb 1988 (PDD 48461). WELLINGTON: Tararua Ranges, vic. Dundas Hut, Pukemoremore summit, on Celmisia sp., P.R. Johnston, 10 Feb 1985 (PDD 49055)), and there remain many other undescribed leotiaceous species on this substrate in New Zealand (P.R. Johnston, unpubl. data).