PDF - CES (IISc)

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REPRODUCTION
formed a wide-stretching hymenium. Several carpogonia took part in the
formation of one apothecium.
The tissue below the ascogonium meanwhile developed vigorously, form-
ing a weft of encircling hyphae, while the upper branches grew vertically towards
the cortex. Gonidia in contact with the developing fruit also increased,
and, with the hyphae, formed the exciple or thalline margin. The growth
upward of the paraphyses raises the overlying cortex which in Anaptychia
is " fibrous "; it gradually dies off and allows the exposure of the disc, though
small shreds of dead tissue are frequently left. In species such as those of
Xanthoria where the cortex is of vertical cell-rows, the apothecial hyphae
simply push their way between the cell-rows and so through to the open.
Baur found the development of the apothecium somewhat similar in the
crustaceous corticolous lichen, Lecanora subfusca. After a long period of
sterile growth, spermogonia appeared in great abundance, and, a little later,
carpogonia in groups of five to ten ; the trichogynes emerged very slightly
above the cortex; they were now branched. The ascogonia were frequently
a confused clump of cells, though sometimes they showed distinct spirals.
The surrounding hyphae had taken a vertical direction towards the cortex
at a still earlier stage, and the brown tips were visible on the exterior before
the trichogynes were formed. The whole growth was extremely slow.
In Physcia stellaris the carpogonia occurred in groups also, though Lin-
dau 1 thinks that, unlike Anaptychia (Physcia} ciliaris, only one is left to form
the fruit. Only one, according to Darbishire 2 , entered into the apothecium
in the allied species, Physcia pulverulenta. In the latter plasma connections
were visible from cell to cell of the trichogyne, and, after copulation with
the spermatium, the ascogonial cells increased in size though not in number
and the plasma connections between them became so wide that the asco-
gonium had the appearance of an almost continuous multinucleate cell or
coenogamete 3 . As in gelatinous lichens, each of these cells gave rise to
ascogenous hyphae.
c. GENERAL SUMMARY. The main features of development described
above recur in most of the species that have been examined.
(i) The carpogonia arise in a complex of hyphae situated on the under
side of, or immediately below the gonidial zone. Usually they vary in number
from five to twenty for each apothecium, though as many as seventy-two
have been computed for Icmadophila ericetorum*, and Wainio 5 describes
them as so numerous in Coccocarpia pellita var., that their trichogynes covered
some of the young apothecia with a hairy pile perceptible with a hand lens,
though at the same time other apothecia on the same specimens were
bsolutely smooth.
1 Lindau 1888.
2 Darbishire 1900.
3 See also p. 180.
4
Nienburg 1908.
5 Wainio i. 1890.