Pseudocyphellaria colensoi (C.Bab.) Vain.
Sticta colensoi Church. Bab., Fl. N.Z. 2: 274, pl. CXIII (1855).
Lectotype [fide Galloway and James loc. cit., p. 294 (1980)]: New Zealand Sine loco. ?J.D. Hooker, BM!
Thallus orbicular to spreading often ± pendulous, 8-20(-30) cm diam. Lobes rounded to linear-enlongate, 10-25 mm wide, to 12 cm long, ± irregularly incised, margins often notched or crenulate, ± ragged or with coarse to verruciform-granular to flattened isidia. Upper surface bright green or yellowish-green or tinged pale bluish-green when wet, pale greenish-grey when dry, slightly undulate to very shallowly faveolate, matt or glossy, minutely scabrid-areolate (×10 lens), occasionally cracked, lacerate, isidiate. Isidia coarse, verruciform-granular or subcoralloid, abraded at apices and exposing yellow, medulla, appearing ± sorediate, marginal and laminal. Medulla yellow. Photobiont green. Lower surface thinly white-tomentose, ± bullate, pale yellowish-buff. Cephalodia in prominent rounded warts. Pseudocyphellae numerous, yellow, crowded, raised in verrucae, 0.1-0.2 mm diam. Apothecia sparse to frequent, 2-10 mm diam., pedicellate, laminal, rarely marginal, disc red-brown, concave to plane, matt, often fissured, with eroded, verruciform-isidiate margins, thalline exciple prominent, pale, verrucose-areolate. Ascospores 1-3-septate, colourless, fusiform-ellipsoid (30-)34-40 × 8-11 µm. Chemistry: Pulvinic dilactone, pulvinic acid, calycin, polyporic acid, 2α,3β,22α-triacetoxystictane, 22α,hydroxystictane-3-one (±), 2α-3β-diacetoxystictane-22α-ol, stictane-3β,22αdiol (±), 2α-acetoxystictane-3β,22,α-diol, 3β-acetoxystictane-2α,22α-diol (±), stictane-2α,3β,22α,-triol (±).
N: S: St: A: Throughout, frequent, s.l. to 1000 m on both successional vegetation and forest trees, especially on Nothofagus both east and west of the Main Divide in South I. Rarely on rock in humid habitats in medium to strong light.
Australasian
P. colensoi is one of the largest and most beautiful of the New Zealand lichens and together with P. coronata is the largest of the yellow-medulla species in the genus. It is distinguished from both P. degelii and P. coronata by the marginal and laminal verruciform-granular isidia and by the ragged, linear-laciniate lobes. It is a very common and conspicuous epiphyte of Nothofagus bark and in some forests (e.g., in the Craigieburn State Forest) it is the dominant epiphyte. It is widely used in lichen dying. Babington's description is accompanied by an excellent plate (pl. CXIII) drawn and engraved by Walter Fitch. Other illustrations of P. colensoi appear in Allan [ Tuatara 1: 35, fig. 34 (1948)], as Sticta coronata, Murray [ Tuatara 11: fig. 31 (1963)] as Sticta hirta and an accurate coloured photograph is given in Margin and Child ["Lichens in New Zealand": 117 (1972) pl. 29 and also fig. D of back cover]. Chemistry in this species is discussed by Chin et al., [ J. chem. Soc. Perkin. Trans. 1: 1437-1446 (1973)].
