Porpidia macrocarpa
Porpidia macrocarpa is a species of saxicolous, crustose lichen in the family Lecideaceae.
Taxonomy
It was formally described as a new species in 1805 by the Swiss botanist Augustin Pyramus de Candolle, who originally classified it in the genus Patellaria. It has a long and extensive taxonomic history, having been shuffled to many different genera, and having been described several times under different names by different authors. In 1984, Hannes Hertel and Adolf Josef Schwab transferred it to the genus Porpidia, and it has largely been referred to that name since.Description
Porpidia macrocarpa is a crustose lichen with a variable thallus, typically appearing to thin and continuous, but it can sometimes be thicker and become cracked or divided into small sections. The surface of the thallus is rough and web-like with a colour range from pale grey to greenish-grey. It frequently shows patches or continuous areas of orange to rust-red due to oxidation. The medulla does not react to iodine. The is indistinct at the margins of immersed thalli but becomes wavy, black, and somewhat distinct at the margins of more superficial thalli.The apothecia are up to 3 mm in diameter, usually, abundant, and can be scattered or crowded together. They are constricted at the base with a thick, swollen that is persistent, black, shiny, and raised, ranging from entire to somewhat wavy. The hyphae measure 3–9 μm in diameter. The of the apothecia can be slightly concave to flat or convex, black or brown-black, with a or shiny finish, and sometimes covered with a grey powdery coating. Larger apothecia often appear to divide through the formation of secondary margins within the disc. The is pale brown to olive-brown, and the hymenium measures 80–100 μm tall. The and inner exciple may show a reddish tinge when treated with potassium hydroxide solution.
The are elongated, measuring 16–20 μm in length and 6–11.5 μm in width. The medulla reacts variably to chemical spot tests, sometimes showing a yellowish reaction with potassium hydroxide and an orange reaction with p-phenylenediamine, indicating the presence of stictic and cryptostictic acids.