'Cetraria' xizangensis J. C. Wei & Y. M. Jiang
Nomenclatural data
Acta Phytotax. Sin. 18: 288, 1980. – Type: [China] Xizang, Nyalam, silvicola, ad corticem Betula, alt. 3900 m, 22.06.1966, J. C. Wei & J. B. Chen 1899 (HMAS – holotype, isotype!)
Thallus foliose, dorsiventral, suborbicular to irregular, ca. 1–3 cm in diameter, yellow. Lobes rounded, partly crenulate and undulate and sparsely pruinose in lobe apices, with marginal white to pale yellow granular soredia; the sorediate zone 0.5–2 mm wide. Lower surface yellow to brown, with brown rhizinae. Thallus ca. (95) 139–177 (196) µm thick; upper cortex ca. 21–27 µm, algal layer ca. 21–50 µm, medulla ca. 21–98 µm, lower cortex ca. 17–21 µm. Algal photobiont green, cells ca. 11–17 µm in diameter. Medullary hyphae 3–4 µm; medulla white. Pycnidia and apothecia unknown.
Typical characters. Thallus dorsiventral, yellow on the upper surface and yellow to brown on the lower surface, with marginal white granular soredia. Medulla white, Pd + orange.
Contains usnic acid in the cortex; fumarprotocetraric (major), protocetraric (minor), lichesterinic and protolichesterinic acids in the medulla.
The species is not well known. The present characterization is compiled from the original Latin description (Wei & Jiang 1980) and the study of isotype material. The taxon is said to be similar to Vulpicida pinastri but the medulla and soredia are white and the medullary colour tests with K and Pd are positive (Wei & Jiang 1980). In our opinion 'C.' xizangensis is morphologically very similar to Allocetraria oakesiana but the chemistry of the two taxa is quite different. The Pd reaction on the medulla should be used to distinguish these lichens (positive in 'C.' xizangensis and negative in A. oakesiana). The true generic position of 'C.' xizangensis has yet to be determined as no ascospores nor pycnidiospores have been detected. Still, it is evident that this taxon does not belong to Cetraria s. strict.
Ecology and distribution
Known only from the type locality in Xizang province, China. Grows on trees (Betula) at rather high altitude (3900 m).
Species pages available
Randlane, T., Saag, A. & Obermayer, W. 2001.