Physma A.Massal.
Thallus foliose, homoiomerous, lobate, gelatinous-expanded when wet, leathery, wrinkled when dry. Lobes radiate attached to the substrate by rhizines. Upper surface dark greenish-grey or greenish-brown to bluish, wrinkled-plicate when dry, swollen when wet. Photobiont blue-green, Nostoc. Lower surface uneven, rhizinate. Apothecia sessile or semi-immersed, lecanorine, thalline margin prominent, discs broad, thalline exciple welldeveloped. Ascospores 8 per ascus, colourless, simple, ellipsoid to fusiform, thick-walled, often minutely warted.
Physma is a predominantly tropical genus included in the family Collemataceae with c. 10 described species. Two species occur in New Zealand in damp, shaded, humid habitats. Zahlbruckner [ Denkschr. Akad. Wiss. Wien math.-naturwiss. Kl. 104: 271 (1941)] described a strongly reticulate-ridged species P. reticulatum Zahlbr., from the Cook Is. The genus is discussed by Hue [ Bull. Soc. linn. Normandie 5 sér. 9: 110-137 (1906)] and Dughi [ Bull. Soc. bot. fr. 93: 112-114 (1946)], but is much in need of revision and serious study. At least one undescribed species is known from New Zealand.
