Foliicolous lichens from Madeira, with the description of a new ...

210 THE LICHENOLOGIST Vol. 28
Thallus epiphyllous, farinose but rather compact, with an irregular surface,
matt, pale green with tinges of yellow or blue, continuous over the leaf
surface. Photobiont: most probably a species of the Chlorococcaceae, with
spherical, green cells, 5–12 μm diam.
Apothecia usually numerous, sometimes absent, circular when young,
eventually becoming lobulate, with an irregular edge, 0·15–0·2(–0·3) mm
diam., less than 0·1 mm in height, without any distinct margin, disc very pale
to pale brownish orange, almost white when young; becoming brownish when
old, flat or convex. Excipulum poorly developed, best seen in young apothecia,
almost absent in older ones, hyaline and without crystals, made of a loose
network of branched and anastomosed hyphae, cells without any swelling at
the margin. Hypothecium hyaline, less than 10 μm thick. Hamathecium of
branched and anastomosed paraphyses. Asci of the Byssoloma-type (sensu
Hafellner 1984: 315), 35–4510–15 μm, 8-spored. Ascospores ellipsoid,
3-septate, not constricted at their septa, with a distinct gelatinous halo,
10–142·5–4 μm.
Pycnidia always numerous, sessile, globose, usually distinctly constricted at
their base, 0·1–0·15 mm high, 0·05–0·1 mm diam., sometimes with a spherical
glut of conidia at their apical ostiole, wall white to very pale brown. Conidia
numerous, bifusiform to slightly clavate, 4–51–1·5 μm.
Byssoloma kalbii belongs to a small group of foliicolous Byssoloma species
with tiny apothecia almost devoid of a margin and with 3-septate ascospores.
These species are weak competitors and are usually present in atypical niches,
such as the leaf margins or the fronds of fragile ferns, or at early stages of
the colonization of leaves by foliicolous organisms. Byssoloma kalbii is easily
distinguished from related species by the very pale apothecia, hyaline
hypothecium and the abundant, white globose pycnidia.
The related species are (Vězda 1975b: 426–427, Kalb & Vězda 1990:
445–447, Barillas & Lücking 1991: 314, Lücking 1992: 143):
—Byssoloma subpolychromum Vězda, known from Africa/Tanzania and Zaïre
and from ‘Amerika’ (fide Vězda 1987: 74, but not mentioned in Kalb & Vězda
1990), and which has pale brown to brown apothecia, 0·3–0·5 mm diam. and
a dark brown hypothecium. Pycnidia are also abundant and have a dark brown
wall.
—Byssoloma minutissimum Kalb & Vězda, widespread in Brazil, also found
in Guatemala and Costa Rica, and which has pale ochre apothecia, 0·15–
0·2 mm diam. and a brown hypothecium. Pycnidia have not yet been found in
this species.
Further data about species of Byssoloma with tiny apothecia and hardly
distinct excipulum not producing any crystals can be found in Farkas & Vězda
(1993: 324).
Byssoloma kalbii is known from only one locality in Madeira, where it
colonizes the fronds of the fern Trichomanes speciosum, growing on the ground;
other foliicolous species present on the same phorophyte are Byssoloma
leucoblepharum and Porina leptosperma. The Riba do Seixal shelters the best