PDF - CES (IISc)

i ;o
REPRODUCTION
In the brown Parmeliae, Rosendahl 1 found the same series of apothecial
tissues, but he interprets the course of development somewhat differently:
the basal dark layer or hypothecium he found to be of purely vegetative
origin ; above it extended the lighter-coloured subhymenium ; the ascogenous
hyphae were present only in the second layer of dark tissue immediately
under the hymenium.
In most lichens the primordium of the apothecium arises towards the
lower side of the gonidial zone, the hyphae of which retain the meristematic
character. In Parmeliae, as was noted by Lindau 2 in P. tiliacea, and by
Baur 3 and Rosendahl 1 in other species, the carpogonial groups are formed
above the gonidial zone, either immediately below the cortex as in P. glabra-
tula, or in a swelling of the cortex itself as in P. aspidota, in which species
the external enlargement is visible by the time the trichogynes reach the
surface. In P. glabra, with a development entirely similar to that of P. as-
pidota, no trichogynes were seen at any stage. The position of the primordium
close under the cortex is also a feature of Ramalina fraxinea as described
G. Wolff4 The
trichogynes in that species are fairly numerous.
. by
A further peculiarity in Parmelia acetabulum attracted Baur's 3 attention.
Carpogonia with trichogynes are extremely numerous in that species as are
the spermogonia, the open pores of which are to be found everywhere between
the trichogynes, and yet fertilization can occur but rarely, as disintegrating
carpogonia are abundant and very few apothecia are formed. Baur makes
the suggestion that possibly cross-fertilization may be necessary, or that the
spermatia, in this instance, do not fertilize and that development must
therefore be apogamous, in which case the small number of fruits formed is
due to some unknown cause. Fiinfstuck 5
thought that degeneration of the
carpogonia had not gone so far, but that a few had acquired the power to
develop apogamously. In Parmelia saxatilis only a small percentage of
carpogonia attain to apothecia, although spermogonia are abundant and in
close proximity, but in that species, unlike P. acetabulum, a large number
the more vigorous apothecia seem
reach the earlier stages of fruit formation ;
to inhibit the growth of those that lag behind.
bb. PERTUSARIAE. In Pertusaria, the apothecial primordium is situated
immediately below the gonidial zone; the cells have a somewhat larger
lumen and thinner walls than those of the vegetative hyphae. In the asco-
gonium there are more cells than in Parmelia acetabulum] the trichogynes
are short-lived, and several carpogonia probably enter into the formation of
each apothecium ; the paraphyses arise from the covering hyphae. So far the
course of development presents nothing unusual. The peculiar pertusarian
feature as described by Krabbe 6
, and after him by
1 Rosendahl 1907.
5 Funfstiick 1902.
2 Lindau 1888. 3 Baur 1904.
6 Krabbe 1882. 7 Baur 1901.
7 Baur does not ,
appear
4 Wolff 1905.