Flora of New Zealand Series

Type : Cryptothecia subnidulans Stirt.

Description : Thallus crustose, whitish or greyish, sometimes reddish, spreading, effuse, epruinose, thin, lacking a cortex; isidia sometimes present, soredia absent; a marginal prothallus often present, byssoid, of radiating and interwoven hyphae. Photobiont green, Trentepohlia -like. Ascomata absent. Asci bitunicate, globose to ovoid, solitary or weakly aggregated in loose groups in the medulla, enclosed by a layer of densely branched and interwoven paraphysoids, resembling a cocoon; monosporous to 6–8-spored. Hypothecium and excipular layers absent. Paraphysoid layer 5–10 μm thick, individual paraphysoids to 1 μm diam. Ascospores colourless, muriform with wavy septa, ellipsoidal, ovoid to somewhat curved and often thickened centrally. Conidiomata pycnidia, present or absent, when present superficial, solitary or aggregated in small groups, elevated, black. Conidia bacillar, straight or slightly curved, 3–7 × 1 μm. Para-depsides (gyrophoric and confluentic acids) and β-orcinol depsidones (norstictic and psoromic acids) often present.

Thor (1997) defines Cryptothecia by three synapomorphies: (1) medulla I+ blue in patches; (2) wavy spore septa; (3) paraphysoids only enclosing the asci. Cryptothecia is accommodated in the family Arthoniaceae (Eriksson et al. 2004; Pennycook & Galloway 2004; Eriksson 2005). Twenty-six species are known worldwide, in tropical and subtropical regions where they colonise bark and/or leaves. One species is known from northern New Zealand (Thor 1997).

As Thor (1997) points out, recognition of species of Cryptothecia in the field can be difficult and recommends that crustose lichens from subtropical habitats lacking distinct ascomata and sharing the following characters should be studied for asci and spores: (1) thallus lacking a cortex and with a ±byssoid but dense (not fluffy) thallus; (2) thallus grey or whitish; (3) parts of the thallus paler and/or raised and/or with different texture; (4) prothallus of byssoid hyphae; (5) photobiont Trentepohlia -like. Several lichens with byssoid thalli that at least sometimes lack ascomata may be superficially similar to Cryptothecia and include species of Crocynia, Dichosporidium, Sagenidium, Streimannia and Tibellia. A key to byssoid lichen genera is given in Hafellner & Vězda (1992).