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128 MORPHOLOGY
somewhat irregular. The terminal empty cells are, loosely attached and as
they are eventually abstricted and strewn over the inside of the cup they
give to it the characteristic white powdery appearance.
1
According to Schwendener
development begins by an exuberant growth
of the medulla which raises and finally bursts the cortex; prominent cyphellae
have been thus formed in Sticta damaecornis (Fig. 73). In other species
the swelling is less noticeable or entirely absent. The opening of the cup
measures usually about \ mm. across, but it may stretch to a greater width.
c. PsEUDOCYPHELLAE. In these no margin is formed, the cortex is
simply burst by the protruding filaments which are of the same colour
yellow or white as the medullary hyphae. They vary in size, from a minute
point up to 4 mm. in diameter.
d. OCCURRENCE AND DISTRIBUTION. The genus Sticta is divided into
two sections : (i) Eusticta in which the gonidia are bright-green algae, and
(2) Stictina in which they are blue-green. Cyphellae and pseudocyphellae
are fairly evenly distributed between the sections; they never occur together.
Stizenberger 2 found that 36 species of the section Eusticta were cyphellate,
while in 43 species pseudocyphellae were formed. In the section Stictina
there were 38 of the former and only 31 of the latter type. Both sections of
the genus are widely distributed in all countries, but they are most abundant
south of the equator, reaching their highest development in Australia and
New Zealand.
In the British Isles Sticta is rather poorly represented as follows:
\Eusticta (with bright-green gonidia).
Cyphellate: 5. damaecornis.
Pseudocyphellate: S. aurata.
\Stictina (with blue-green gonidia).
Cyphellate: S.fidiginosa, S. limbata, S. sylvatica, S. Dufourei.
Pseudocyphellate: 5. intricata van Thouarsii, S. crocata.
Structures resembling cyphellae, with an overarching rim, are sprinkled
over the brown under surface of the Australian lichen, Heterodea Miilleri;
the thallus is without a lower cortex, the medulla being protected by thickly
woven hyphae. Heterodea was at one time included among Stictaceae,
though now it is classified under Parmeliaceae. Pseudocyphellae are also
present on the non-corticate under surface of Nephromium tomentosum,
where they occur as little white pustules among the brown hairs; and the
white impressed spots on the under surface of Cetraria Islandica and allied
species, first determined as air pores by Zukal 3 have also , been described by
Wainio 4 as pseudocyphellae.
1 Schwendener 1863, p. 169.
2
Stizenberger 1895.
3 Zukal 1895, p. 1355.
4 Wainio 1909.