Placopsis clavifera
≡Placopsis alphoplacoides var. clavifera I.M.Lamb, Lilloa 13: 236 (1947).
≡P. trachyderma var. clavifera (I.M.Lamb) P.James in A.F. Mark et al. N .Z. J. Bot. 2: 82 (1964).
Description : Thallus closely attached, irregularly spreading in thick, tartareous patches, often binding together soil, sand and small stones, or ±orbicular when overgrowing large stone or rocks, (1–) 2–6(–10–20) cm diam., without a marginal prothallus. Lobes (0.2–) 0.5–1(–2) mm wide, 5–12 mm long at margins, strongly convex, adjacent to contiguous from margins to centre, centrally complex-imbricate to areolate. Margins markedly effigurate when attached to stones slightly swollen, subflabellate, scalloped or notched, often suffused dark-brown. Upper surface smooth, to somewhat glossy in parts, generally matt, here and there with minute, spreading cracks, pale-greenish or creamish when moist, pale brown-pink when dry, with scattered, white, round to irregular pseudocyphellae, 0.01–0.03 mm diam., often most noticeable on convex, marginal lobes; without pruina or soredia; distinctly and often prominently isidiate. Isidia cylindrical to subglobose to flattened to subcoralloid when well developed, projecting from surface, swollen at apices, (0.2–)0.5–2.5(–10) mm tall, concolorous with thallus or paler, matt, without pseudocyphellae, rarely developing terminal apothecia when very well developed. Cephalodia subglobose at first and somewhat immersed in thallus or obscured by growth of isidia, central, rarely at margins, round, 1 mm diam., subglobose, smooth at first, becoming plicate-effigurate, shallowly to deeply grooved and fracturing into "islands" with age, 2–6 mm diam., dark purplish blue whem moist, pale to dark red-brown to ochre-coloured when dry, epruinose. Apothecia frequent to absent, sessile, constricted at base, round, (0.5–)1–3 mm diam., disc pale to dark red-brown when moist, ochre-brown to grey-brown when dry, noticeably roughened and radiate-cracked and with a thin greyish pruina. Thalline margin thick, swollen, 0.1–0.4 mm diam., concolorous with thallus, roughened to smooth, occasionally developing projecting isidia. Proper margin thin, slightly raised above disc, pale-pinkish, dull, noticeably paler than disc. Epithecium densely granular, olive-brownish, 25–35 μm thick. Hymenium pale-pinkish in fresh material, 95–130 μm tall, inspersed with oil droplets. Paraphyses slender, rarely branched, 1.5–3 μm diam., apices not swollen or moniliform. Hypothecium opaque, pale yellow-brown to pale-pinkish, 80–95 μm thick. Asci cylindrical–clavate, 90–120 × 15–17 μm. Ascospores broadly ellipsoidal, (11–)18–27 × 8–11.5 μm, contents vacuolate. Pycnidia prominent, laminal, swollen, projecting above thallus surface, 0.05–0.1 mm diam., apical ostiole red-brown, often gaping, surrounded by a roughened–verrucose margin. Conidia slightly curved, filiform, 25–30 × 1–1.5 μm.
Chemistry : Thallus K−, C+ red, KC+ red, Pd−; containing gyrophoric acid.
N: South Auckland (Moerangi, Kuratau), Taranaki (Mt Taranaki). S: Nelson (Mt Arthur, Flora Saddle, Maruia River), Westland (Otira, Fox Glacier, Paringa River, Haast River), Canterbury (Lewis Pass, Lewis River, Boyle River, Arthur's Pass, Bealey River, Hawdon River, Clyde River, Havelock River, Murchison River, Tasman River, Lake Tekapo, Lake Ohau), Otago (Hunter River, E Matukituki Valley, Dart River, Lammermoor Ra., Pulpit Rock, Silver Peaks, Maungatua), Southland (Homer Saddle, Cascade Creek, Lake Hankinson, Lake Te Anau, Cascade Cove, Dusky Sound, Percy Saddle, Borland Saddle, Borland Burn, S. Branch) St: (Marton's Creek, Mason Bay). Most commonly seen on glacial or river silt and gravel where it forms spreading rosettes to 10(–20) cm diam. It is most commonly associated with other species of Placopsis, including P. elixii, P. hertelii, P. illita, P. perrugosa, P. pruinosa, P. salazina, P. trachyderma. The often extensive tartareous crusts [aptly named by Hugh Wilson as "cowpat lichens" (Wilson 1978: 277)] appear to be of importance in consolidating fluvial detritus as, when lifted from the surface, many small pebbles always adhere to the underside of the thallus (Galloway 1985a: 409, 2001a, 2004a). It is known also from Tasmania (Kantvilas 1989, 1994b; Kantvilas & Jarman 2000; McCarthy 2003c, 2006).
Australasian
Illustrations : Lamb (1947: pl. XVI, fig. 52 – as Placopsis alphoplacoides var. clavifera); Kantvilas & Jarman (1999: 109 – as Placopsis trachyderma var. clavifera); Johnson (2005: 30, fig. 1).
Placopsis clavifera is characterised by: the distinctive, cylindrical to clavate isidia; the thick, tartareous, spreading thallus; and curved, filiform conidia, 12–16 × 0.5 μm present in verrucose thalline pycnidia. It is closely similar in other characters to P. trachyderma (Kremp.) P.James, with which it forms a species-pair. Lamb (1947: 237), who had a rather wide species concept in Placopsis, noted "...This variety [i.e. P. alphoplacoides var. clavifera] seems to be often closely associated with the typical non-isidiate form, but no intergrades were observed by me in the copious material studied". Closely similar to P. trachyderma (q.v.) but distinguished by the pinkish, reddish to brown-pink disc, white-pruinose spots on thallus, and especially on convex marginal lobes of saxicolous forms. On exuberant material from Mt Arthur (Nelson) isidia can reach 1 cm in height and support one or more apothecia! When this lichen spreads onto rock from soil it becomes rosette-forming with distinctive, convex, contiguous lobes with scattered (mottled) areas of white effigurate pruina – these are also seen on basal crusts of soil forms as well. Formation of isidia appears to be depressed when P. clavifera grows on stones and rocks. P. clavifera is similar in habit, ecology and morphology to the southern South American species P. pycnotheca I.M.Lamb ex Räsänen (Räsänen 1939; Lamb 1947; Galloway 2002d), but is distinguished from it by differences in ascospore size and isidium morphology.
