Pyxine philippina
Pyxine philippina is a species of foliose lichen in the family Caliciaceae. It was first discovered in the Philippines, growing on tree bark in the mountainous regions of Luzon. The lichen forms a thin to moderately thick, leaf-like body with a whitish upper surface and blackish underside, anchored by short root-like structures called rhizines. Since its original description, it has been widely documented across Asia, including in Bhutan, India, Japan, Nepal, and Thailand.
Taxonomy
Pyxine philippina was first described scientifically by the Finnish lichenologist Edvard August Vainio in 1913. The species epithet philippina refers to its type locality in the Philippine Islands. Vainio noted that this species is closely related to Pyxine denudatula, from which it can be distinguished by differences in the colour of the . The species also shows some similarities to Pyxine retirugella, but differs in having a rather than thallus with a granular margin.Description
Pyxine philippina is a foliose lichen, meaning it has a leaf-like growth form. The thallus is thin to moderately thick and lacks both soredia and isidia. The upper surface is whitish, fairly opaque, and , appearing smooth. The medulla is white. When tested with potassium hydroxide solution, the upper surface turns lutescent, followed by rubescent. The measure 0.5–1.4 mm in width and are irregular in shape, somewhat contiguous, and confluent, often very confluent. They are flat or partially convex, appearing blackish beneath. The rhizines are short and blackish in colour.The apothecia measure 1–4 mm in width and are in form. The margin is blackish or occasionally ashy-blackish in colour, fairly slender or of moderate thickness, whilst the is flat, black, and nude. The has an interior that is verdigris to sooty coloured and reacts strongly to potassium hydroxide, or occasionally appears whitish to ashy.
The is distinctly brownish above and shows no reaction to potassium hydroxide, whilst appearing whitish below or occasionally becoming ashy. The spores, which number eight per ascus, are arranged in two rows, appearing brownish, oblong, and blunt to . The spores are divided by a single cross-wall with membranes that are unequally thickened, particularly in the apices and at the septum, measuring 15–23 micrometres in length and 6–8 μm in width.