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Acarospora nitida H. Magn.
Family: Acarosporaceae
Acarospora nitida image

Thallus determinate, radiate, pitch black or dark brown/grayish-brown-black, outline indistinct, lobate, for the most part in discrete semiglobose, verrucae, dissolute, tightly adnate, pale below.

Apothecia solitary in each central areole or sometimes a few, immersed, disc punctiform, impressed, concolourous with thallus, ornate.  Upper cortex somewhat thick, CaCl-, medulla crystals dark.  Hymenium somewhat thick.  Paraphyses thick.  Spores broadly ellipsoid.

The single thalli dispersed upon the stone, about 1 cm in diam., +/- circular, only few, very convex marginal lobes developed, 1-1.5 mm long and about 0.5 mm broad, partly sinuate at the apices, firmly affixed.  Central verrucae somewhat regularly half globose and 0.5-0.7(1) mm in diam., 0.3-0.4 mm thick, their cortex, especially round the base, destroyed so that the white medulla is visible, often as a narrow ring at the base.  (Fig. 7).

Upper cortex 35-45(50) µ thick, transparent, exterior 8-12 µ very dark brown, amorphous stratum 5-7 µ thick, regularly developed, even.  Cortical cells indistinct, also in KOH or HCl, 1.5-3 µ in diam., irregular, hyphae apparently intricate.  Gonidia 7-13 µ in diam., stratum 50-75 µ thick, continuous, with even surface.  Medulla 100-400 µ thick, gray from granules on the hyphae.  These 3-4 µ thick, in KOH or HCl indistinctly thick-walled, very long-celled and very loosely intricate.  Marginal cortex dark brown, areolae largely attached to the stone with the medulla.

Apothecia at first in the shape of a slight depression at the top of the verruca, solitary, finally somewhat prominent and simple with rough disc, 0.3-0.4 mm large, or consisting of 2-5 very minute, punctiform apothecia.—Exciple 10-15 µ thick at the bottom, widened towards the surface, sometimes the exciples of approaching apothecia touching one another.  Hypothecium 20-30 µ thick, I+ dark blue, little developed.  Hymenium 85-110 µ high, upper 20-30 µ blackish brown; I+ greenish or pale blue.  Paraphyses 2-3 µ thick, apices KOH+ dark brown, 3-4 µ thick.  Asci 65-70 X 25 µ, easily bersting (sic).  Spores about 100, 3-4.5 X 1.7 (2) µ, somewhat broadly ellipsoid, especially as young.

Habitat.  On non-calciferous mica-schist with a specimen of Sporastatia testudinea and traces of Caloplaca and Gyrophora, but most part of the stone devoid of lichens.

Locality.  East Greenland.  Franz Josef Fjord: Reinbukta, 1929, Lynge.

One of the most curious species I have met with in this genus, through colour and marginal lobes reminding of a meagre species of A. molybdina, but quite different from that species in structure.