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336
An excellent species, differing already in habitus from all others
on account of the blackish colour, the somewhat indistinetly lobate
thalline margin and the very small irregular apothecia. The short
and broad spores is also a good characteristic.
6. Acarospora helvetica H. Magn. n. sp.
Thallus continuus, ambitu radiatim areolatus, centro diffracto-
areolatus, fusco-castaneus, opacus, areolae minutae, tenues, angulatae,
planae, subtus pallidae. Apothecia erebra, singula vel pauca, discus
obscure fuscus, planus. Hymenium angustum. Sporae late ellip-
soideae.
Thallus forming more or less confluent areas, in the circumference
mostly more or less distinctly radiate-areolate, with thin angulose
sterile areolae, towards the centre diffract-areolate, abundantly
fertile. All areolae concolorous, dark brown, 0.5—1 mm. in diam.
and 0.2—0.3 mm. thick, opaque, plane, angulose, separated by
distinct and wide cracks, unaltered by KOH, CaCl,O, and J, largely
alfixed to the substratum with rather pale lower surface.
Cortex 15—30 u, upper 4—8 u dark brown with no or very
thin amorphous stratum. Hyphae intricate, moderately pachyder-
matous, lumina 2.5—4 u large, irregular. Gonidia yellowish green,
8—20 u in diam., in a 30—40(—80) u thick, mostly unbroken,
not dense stratum. Medulla up to 200 u thick, white, somewhat
closely contexted, hyphae leptodermatous, lumina more or less round
or somewhat irregular, 3—5 w in diam. Marginal cortex 5—8 4,
dark brown, going in on the lower side only very narrowly and
therefore lower side mostly pale.
Apothecia more or less abundant towards the centre, one or few
in each areola, disc at first impressed, reddish, surrounded by a
thalline wall-like margin, then almost plane, dark brown to blackish
with disappearing margin, round or angulose 0.2—0.5 mm. broad.
Excipulum thin, 5—9 u, or in older apothecia up to 50 iu broad,
yellowish, confluent with hypothecium and coloured dark blue with
J. Cells very pachydermatous, lumina round or stretched, 2—3 u.
Somelimes a distinct hypothecium, 20—35 u, has been observed.
Hymenium 75—85(—100) u, white, upper 8 u dark yellowish brown,
with J coloured at first blue, soon dirty red. Paraphyses coherent,
1.7—2 u thick, often branched, brownish capitate, 4 a, in KOH
more distinetly so, midmost articles 6—8 u. Asci and spores not
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