PDF - CES (IISc)

202
REPRODUCTION
spermatia and, generally, with a mass of mucilage that swells with moisture
and secures their expulsion.
The spermatia of lichens are colourless and are provided with a cell-wall
and a nucleus. The presence of a nucleus was demonstrated by Holier 1 in
the spermatia of Calicium parietinum, Opegrapha atra, Collema micropkyllum,
C.pulposum and C. Hildenbrandii, and by Istvanffi 2 in those of Buellia punctiformis
(B. myriocarpa), Opegrapha subsiderella, Collema Hildenbrandii, Calicium
trachelinum,Pertusaria communis andArt&oma communis (A. astroided).
Istvanffi made use of fresh material, fixing the spermatia with osmic acid,
and in all of these very minute bodies he demonstrated the presence of a
nucleus which stained readily with haematoxylin and which he has figured
in the spermatia of Buellia punctiformis as an extremely small dot-like
structure in the centre of the cell. On germination, as in the cell-multi-
plication of other plants, the nucleus leads the way. Germination is preceded
by nuclear division, and each new hyphal cell of the growing mycelium
receives a nucleus.
c. GERMINATION OF SPERMATIA (pycnidiospores). The strongest argu-
ment in favour of regarding the spermatia of lichens as male cells had always
been the impossibility of inducing their germination. That difficulty had at
length been overcome by Moller 1 who cultivated them in artificial solutions,
and by that means obtained germination in nine different lichen species.
He therefore rejected the commonly employed terms spermatia and spermogonia
and substituted pycnoconidium and pycnidia. Pycnidiospore has
been however preferred as more in accordance with modern fungal termi-
nology. His first experiment was with the "spermatia" of Buellia punctiformis
(B. myriocarpa) which measure about 8-10/1. in length and about 3 ^ in
width, and are borne directly on the septate spermatiophores (arthrosterigmata).
In a culture drop, the spore had swelled to about double its size by
the second or third day, and germination had taken place at both ends, the
membrane of the spore being continuous with that of the germinating tube.
In a short time cross septa were formed in the hyphae which at first were
very close to each other. While apical growth advanced these first formed
cells increased in width to twice the original size and, in consequence, became
slightly constricted at the septa. In fourteen days a circular patch of mycelium
had been formed about 280/1 in diameter. The development exactly
resembled that obtained from the ascospores of the same species grown in the
absence of gonidia. The largest thallus obtained in either case was about
2mm. in diameter after three months' growth. The older hyphae had a
tendency to become brownish in colour; those at the periphery remained
colourless. In Opegrapha subsiderella the development, though equally
1 Moller 1887.
2 Istvanffi 1895.