Flora of New Zealand Series

≡Endocarpon squamulosum Ach., Methodus: 126 (1803).

≡Catapyrenium squamulosum (Ach.) Breuss, Ber. Dtsch. Bot. Ges. 98: 389 (1985).

≡Dermatocarpella squamulosa (Ach.) Harada, Nat. Hist. Res 2 (2): 139 (1993).

Description : Flora (1985: 156 – as Dermatocarpon lachneum); Breuss (1993a: 31; 2001c: 170).

N: Sine loco, on calcareous soil, W. Colenso (BM). S: Nelson (Dolomite Point, Pancake Rocks), Canterbury (Castle Hill), Southland (Clifden). P. squamulosum occurs at the base of limestone outcrops and in crevices on calcareous soil, with Fulgensia fulgens and Psora decipiens. It should be looked for also among mosses on old mortar in old walls. It is the most widespread species of Placidium being known from all continents except Antarctica (Breuss 1993, 1995, 2001c, 2002d; Mies & Schultz 2004).

Cosmopolitan

Illustrations : Wirth (1987: 114); Dobson (1992: 91; 2000: 105); Harada (1993a: 138, fig. 15B, D; 140, fig. 17A–I); Goward et al. (1994b: 35, fig. 3A) [all as Catapyrenium squamulosum]; McCarthy & Malcolm (2004: 56); Sérusiaux et al. (2004: 142).

Placidium squamulosum is characterised by: the saxicolous (basicolous rocks) habit; ±adnate squamae, medullary tissue of "Mischtyp" [the hyphal cells being strongly swollen to form globular lumina giving the tissue a ±cellular appearance (Breuss 1993: 18)]; sparse to dense rhizohyphae; a pale excipulum; small spores [12–16 × 5.5–7.5 μm]; pycnidia Dermatocarpon -type (Harada 1993a: 141) with oblong–ellipsoidal conidia [2.5–4 × 1.3–2 μm]. In the earlier literature it was commonly referred to as Dermatocarpon hepaticum. The name Catapyrenium lachneum (=P. lachneum) was used in a broad sense for Southern Hemisphere collections of P. squamulosum, but true P. lachneum is restricted to the Northern Hemisphere in strictly arctic–alpine habitats (Breuss 1995: 178).