Pseudocyphellaria crocata (L.) Vain.
Lichen crocatus L., Mant. Pl.: 310 (1771).
Thallus 5-7(-10) cm diam., rigid, lobate, attached centrally, margins mainly free. Lobes ± broadly rounded to deeply laciniate, margins partly imbricate, apices rounded or incised, crenulate to sinuous, often subascendent, not isidiate or phyllidiate. Upper surface pale brownish-yellow with greenish tint, to red-brown or dark chocolate brown, ± densely reticulate-faveolate, ridges strongly defined, lacunae deep or shallow, shining, ridges with ± numerous low warts bursting into yellow soredia, often confluent and spreading, usually smaller or lacking at margins. Medulla white. Photobiont blue-green. Lower surface densely tomentose to margins, pale ochraceous-buff at margins, dark brown to blackish centrally, sometimes margins ± reticulate with yellowish-buff ridges and bullae visible. Pseudocyphellae yellow, scattered, sparse to ± frequent, 0.2-0.4 mm diam., ± sunk in tomentum, punctiform near margins. Apothecia rare, 1-2 mm wide, sessile on ridges, disc deep red-brown or blackish, occasionally faintly pruinose, concave to plane, margins thin, pale reddish-brown, ± smooth to wrinkled. Ascospores 1-septate, (18-)22-30 × 5-9(-12) µm. Chemistry: Pulvinic lactone, pulvinic acid, calycin, methyl virensate, 5-chloromethyl-virensate, hopane-6α, 7β-triol, norstictic, constictic and stictic acids. In c. one fifth of specimens examined stictic acid is replaced by salazinic acid (cf. P. neglecta).
N: S: St: Throughout, common, on rocks in open grassland, and on twigs or bark of lowland trees and shrubs or at treeline in subalpine habitats.
Cosmopolitan
P. crocata is characterised by a blue-green photobiont, white medulla, yellow pseudocyphellae and yellow soralia. It is often difficult to make a strict segregation of individuals with a ± even, plane upper surface from those having well defined faveolae. Morphological variation ranges from elongate, narrow lobes and a smooth upper surface (forms often called P. mougeotiana) to lobes which are broad and overlapping with conspicuous and often deep faveolation. Soralia are also variable, ranging from exclusively marginal (labriform granular-subcorticate to powdery sorediate) to laminal, especially in faveolate forms where soralia are confined to ridges and also inter-ridge lacunae, to smooth-surfaced forms where soredia tend to be randomly distributed on the upper surface. In contrast to the considerable variation in morphology, the chemistry in this species is remarkably uniform. P. crocata is related to P. neglecta but distinguished from it by the entire margins which lack phyllidia. It is also much less fertile. A coloured photograph (as P. mougeotiana) is given in Martin and Child ( loc. cit., p. 118, pl. 30).
