Germination was also observed in a species of _Arthonia_, the spores of
which had begun to grow while still in the pycnidium. The most complete
results were obtained in species of _Calicium_: in _C. parietinum_ the
spores, which are ovoid, slightly bent, and brownish in colour, swelled
to an almost globose shape and then germinated by a minute point at the
junction of spore and sterigma, and also at the opposite end; very rarely
a third germinating tube was formed. Growth was fairly rapid, so that
in four weeks there was a loose felt of mycelium measuring about 2 cm.
× 1 cm. and 1 mm. in depth. Parallel cultures were carried out with the
ascospores and the results in both cases were the same; in five or six
weeks small black points appeared, which gradually developed to pycnidia
with mature pycnidiospores from which further cultures were obtained.
On _C. trachelinum_, which has a thin greyish-white thallus spreading
over old trunks of trees, the pycnidia are usually abundant. Lindsay had
noted two different kinds and his observation was confirmed by Möller.
The spores in one pycnidium are ovoid, measuring 2·5-3 µ × 1·5-2 µ;
in the other rarer form, they are rod-shaped and 5-7 µ long. In the
artificial cultures they both swelled, the rod-like spores to double
their width before germination, and sometimes several tubes were put
forth. Growth was slow, but of exactly the same kind from these two types
of spores as from the ascospores. At the end of the second month pycnidia
appeared on all the cultures, in each case producing the ovoid type of
spore.
In a second paper Möller[729] recorded the partially successful
germination of the “spermatia” of _Collema_ (_Leptogium_) _microphyllum_,
the species in which Stahl had demonstrated sexual reproduction. Growth
was extraordinarily slow: after a month in the culture solution the first
swelling of the spermatium prior to germination took place, and some time
later small processes were formed in two or three directions. In the
fourth month a branched filament was formed.
Möller’s experiments with ascospores and pycnidiospores were primarily
undertaken to prove that the lichen hyphae were purely fungal and
parasitic on the algae. A series of cultures were made by Hedlund[730] in
order to demonstrate that the pycnidiospores were asexual reproductive
bodies; they were grown in association with the lichen alga and their
germination was followed up to the subsequent formation of a lichen
thallus.
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