Flora of New Zealand Series

≡Lecanora trachyderma Kremp., Verhandl. zool.-bot. Ges. Wien 26: 451 (1877).

=Placopsis alphoplacoides I.M.Lamb, Lilloa 13: 234 (1947).

Holotype: New Zealand. Sine loco, Charles Knight – M 123–80/8.

Description : Flora (1985: 408).

Chemistry : Thallus K−, C+ red, KC+ red, Pd−; containing gyrophoric acid.

S: Nelson (Maruia River), Westland (Fox Glacier, Haast River), Canterbury (Arthur's Pass, Bealey River, Hawdon River, Waimakariri River, Havelock River, Cameron Glacier), Otago (Hunter River, Dart River), Southland (Takitimu Ra., Lake Te Anau). On pebbles, gravel and silt in braided riverbeds, and on old moraine surfaces. An active soil consolidator in these disturbed environments and commonly associating with other species of Placopsis, viz. P. clavifera, P. elixii, P. hertelii, P. perrugosa and P. pruinosa.

Australasian

Illustrations : Lamb (1947: pl. XVI, fig. 50 – as Placopsis alphoplacoides); Johnson (2005: 30, fig. 1).

Placopsis trachyderma is characterised by: a thallus of congested, subglobse to hummocky, areolae or squamules developing on a dark-brown to blackish basal prothallus closely attached to substratum, but not or rarely visible at margins; sessile, rounded apothecia 1–2 mm diam., with a brown to dark-brown, epruinose disc; cylindrical asci; narrowly ellipsoidal ascospores partly biseriate in ascus, (18–) 20–23(–25) × 5–7 μm, wall smooth, 1–1.5 μm thick.