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Lichens (1985) - Flora of New Zealand Lichens
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Arthonia Ach.

ARTHONIA Ach., 1806  nom. cons. 

Thallus crustose, effuse, ecorticate or immersed, corticolous or foliicolous or lichenicolous. Photobiont green, Trentepohlia, Phycopeltis or in Chlorococcaceae. Ascocarps adnate to sessile or immersed, immarginate, presenting a somewhat "rubbed-down" appearance, rounded to irregular, stellate or ± lirelline. Ascospores colourless to brown, transversely septate (1-8-septate), obovate to fusiform, very variable, 2-8 per ascus.

Key

1
Ascocarps pruinose
2
Ascocarps epruinose
3
2
Ascocarps ± lirelliform or bluntly stellate, disc pink- or red-pruinose
tumidula
Ascocarps round or oblong, disc grey-white-pruinose
platygraphella
3
Ascocarps ± stellate
4
Ascocarps round to irregular-oblong
5
4
Spores 1-septate
dispersa
Spores 3-septate
subramulosa
5
Thallus whitish or pale greenish or greyish
6
Thallus olivaceous, greenish or grey-black
9
6
Spores 1-septate
7
Spores 4-7-septate
8
7
Spores 29-33 × 12-15 µm
conspicua
Spores 40-56 × 25-32 µm
diaphora
8
Spores 4-septate
nigrocincta
Spores 7-septate
epiodes
9
Ascocarps minute, less than 0.3 mm diam.
10
Ascocarps 0.6-1.5 mm diam.
11
10
Ascocarps discrete, spores 4-septate
phymatodes
Ascocarps in ± parallel lines, spores 3-septate
indistincta
11
Spores 5-septate, 24-32 × 9-12 µm
peraffinis
Spores 3-7-septate, 23 × 8 µm
knightii

Arthonia is a large cosmopolitan genus with c. 500 species described. Some species are non-lichenised fungi living as parasymbionts or parasites on lichens, or as saprophytes [Santesson Symb. bot. upsal.12: 68-91 (1952)]. Problems of nomenclature in the genus are discussed by Santesson ( loc. cit. pp. 68-75). Twelve species are recorded from New Zealand, but the genus is still very poorly collected and understood here.

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