Pyxine subcinerea is a species of foliose lichen in the family Caliciaceae. It has a pantropical distribution, and typically grows on bark, but less commonly on rocks. The lichen is characterised by its yellow medulla, soralia on the margins on the lobes that make up the thallus, and the presence of the chemical lichexanthone in the cortex.
Taxonomy
The lichen was first formally described by the Scottish scientist James Stirton from specimens collected in Queensland, Australia. He noted that its thallus was similar to that of Pyxine sorediata, but Stirton distinguished it from that species by the "internal organization of both the thallus and the apothecia", as well as the negative K reaction of the thallus, compared to the yellow reaction of P. sorediata.
Synonyms of Pyxine subcinerea include: Physcia melanenta, described by Charles Knight in 1882; Pyxine chrysanthoides, described by Edvard August Vainio in 1915 from material collected in the Antilles; Pyxine meissneri var. sorediosa, described by Johannes Müller Argoviensis in 1879; and Pyxine cocoes var. caesiopruinosa, described by Edward Tuckerman in 1869 (and later promoted to distinct species status as Pyxine caesiopruinosa by Henry Andrew Imshaug in 1957).
Description
Closeup of lobes; the scale bar is 0.5 mm.
The thallus of Pyxine subcinerea is 3–8 cm (1.2–3.1 in) wide, with an upper surface ranging in colour from yellowish grey to grey to brownish grey or olive-grey. The lobes that comprise the thallus are 0.3–1.5 mm (0.01–0.06 in) wide, somewhat tightly apressed to the substrate and are more or less flat but often somewhat concave near the tips. The lobe surface are pruinose, with the pruina resembling dense points near the lobe tips. These pruina contain weddellite, a mineral form of calcium oxalate. There are distinct pseudocyphellae at the margins of the lobes. The soralia are near the lobe margins. The medulla is quite thin and yellow above. The lower surface is black in...
