PDF - CES (IISc)

REPRODUCTION IN DISCOLICHENS 163
original cell nucleus. In the same cell, lying close against the lower septum
and partly within the opening, there was a mass of chromatin material which
might be the male nucleus migrating downwards. The next point of interest
was observed in the twelfth cell from the tip in which there were two nuclei,
a larger and a smaller, the latter judged to be the male cell, the small size
being due to probable division of the spermatium nucleus either before or
after leaving the spermatium. It is stated however that the spermatium
was always uninucleate. Meanwhile the cells of the ascogonium had
increased in size, the perforations of the septa between the cells became
more evident, and their nuclei persisted. In one cell at this stage two nuclei
were present, one of the two presumably a male nucleus; no fusion of nuclei
was observed in the ascogonial cells. Later the cross walls between the
cells were seen to have disappeared more completely and migration of
nuclei had taken place, so that some of the cells appeared to be empty while
others were multinucleate. Considerable multiplication of the nuclei occurred
before the ascogenous hyphae were formed : twelve nuclei were observed in
a part of the ascogonium which was just beginning to give off a branch.
Several branches might arise from one cell, and their cells were either uni-
or binucleate, the nuclei being larger than those of the vegetative hyphae.
The formation of the asci was not distinctly seen, but young binucleate
asci were not uncommon. The fusion of the two nuclei was followed by
the enlargement of the ascus and the subsequent nuclear division for spore
formation. In the first heterotypic division twelve chromosomes, double the
number observed in the vegetative nucleus, were counted on the equatorial
plate. In the third division they were reduced to the normal number of six,
from which F. Bachmann concludes that a twofold fusion must have taken
place
in the ascogonium and again in the ascus.
Spiral or coiled ascogonia were observed by Wainio 1 in the gelatinous
crustaceous genus Pyrenopsis, but the trichogynes did not reach the surface.
In Lichina-, a maritime gelatinous lichen where the carpogonia occur in
groups, trichogynes have not been demonstrated.
A peculiarity of some gelatinous lichens noted by Stahl 3 and others in
species of Pkysma, and by Forssell 4 in Pyrenopsis and Psorotichia, is the
development of carpogonia at the base of, and within the perithecial walls
of old spermogonia. No special significance is however attached to this
phenomenon, and it is interesting to note that a similar growth was observed
by Zukal 5 in a pyrenomycetous fungus, Pleospora collematum, a harmless
parasite on PJiysma compactum and other Collemaceae. The structures invaded
were true pycnidia of the fungus as the minute spores were seen to
germinate. A " Woronin's hypha " at the base of several of these pycnidia
developed asci which pushed up among the spent sporophores.
1 Wainio i. 1890.
2 Wolff 1905.
3 Stahl 1877.
4 Forssell 1885'-.
a Zukal 1887, p. 42.
II 2