PDF - CES (IISc)

1 64
REPRODUCTION
b. CARPOGONIA or NON-GELATINOUS LICHENS. The soft loose tissue
of the gelatinous lichens is more favourable for the minute study of apo-
thecial development than the closely interwoven hyphae of non-gelatinous
forms, but Borzi 1 had already extended the study to species of Parmelia,
Anaptychia, Sticta, Ricasolia and Lecanora, and in all of them he succeeded
in establishing the presence of ascogonia and trichogynes. After him a
constant succession of students have worked at the problem of reproduction
in lichens.
Lindau 2
published results of the examination of a considerable series of
lichens. In Anaptychia (Physcia) ciliaris, Physcia stellaris, Ph. pulverulenta,
Ramalina fraxinea, Placodium (Lecanora) saxicolum, Lecanora subfusca and
Lecidea enteroleuca he demonstrated the presence of ascogonia with tricho-
gynes. In Parmelia tiliacea and in Xanthoria parietina he found ascogonia
but failed to see trichogynes. In none of the species examined by him did
he observe any fusion between the trichogyne and a spermatium.
In Anaptychia ciliaris he was able to pick out extremely early stages by
staining with a solution of chlor-zinc-iodine.
3 Maule applied the same test
to Physcia pulverulenta, but found that to be successful the reaction required
some time. Certain cells of the hyphae mostly
terminal cells in the lower area of the gonidial
zone and even occasionally in the pith (according
to Lindau) coloured a deep brown, while the
Fig. 93. Pkyscia pulverulenta Nyl.
Vertical section of thallus and
carpogonium before fertilization.
a, outer cortex; b, inner cortex;
c, gonidial 1 ayer ; d, medulla,
x ca. 540 (after Darbishire).
ordinary thalline hyphae were tinted yellow.
He assumed that these were initial ascogonial
cells on account of the richer plasma contents,
and also because of the somewhat larger size of
the cells. In the same region of the thallus
young carpogonia were observed as outgrowths
from vegetative hyphae, though the trichogynes
had not yet reached the surface.
At a more advanced stage the carpogonia
were seen to be embedded in the gonidial zone
and occurred in groups. The cells of the asco-
gonium, easily recognized by the darker stain,
were short and stout, measuring about 6-8 /j, in
length and 4*4 p, in width. They were arranged
in somewhat indistinct spirals; but the crowding
of the groups resulted in a confused intermingling of the various generative
filaments. The trichogynes composed of longer narrower cells rose above
the hyphae of the cortex; they also stained a deep brown and the projecting
cell was always thin-walled. Lindau frequently observed spermatia very
1 Borzi 1878.
2 Lindau 1888. 3 Maule 1891.