PDF - CES (IISc)

HYMENOLICHENS 153
recognized its affinity with Thelephora, a genus of Hymenomycetes. Later
Johow 1 went to the West Indies and studied the Hymenolichens in their
native home. The genera and species described by Johow have been
reduced to Cora and Dictyonema ;
by Wainio 2 .
a new genus Corella has since been added
Johow found that Cora grew on the mountains usually from 1000 to
2000 ft. above sea-level. As it requires for its
development a cool damp climate with strong
though indirect illumination,
neither 1
it is found
in sunny situations nor in the depths
of dark woods. It grows most freely in diffuse
light, on the lower trunks and branches of
trees in open situations, but high up on the
stem where the vegetation is more dense.
It stands out from the tree like a small thin
bracket fungus, one specimen placed above
another, with a dimidiate growth similar to
that of Polystictus versicolor. Both surfaces
are marked by concentric zones which give
it an appearance somewhat like Padina Pa-
vonia. These zones indicate unequal intercalary
growth both above and below. The
whole plant is blue-green when wet, greyishwhite
when dry, and of a thin membranaceous
consistency.
B. STRUCTURE OF THALLUS
There is no proper cortex in any of the
genera, but in Cora there is a fastigiate
branching of the hyphae in parallel lines
towards the upper surface; just at the outside
they turn and lie in a horizontal direction,
and, as the branching becomes more profuse,
a rather compact cover is formed. The gonidia,
which consist of blue-green Chroococcus
cells, lie at the base of the upward branches
and they are surrounded with thin-walled short-celled hyphae closely interwoven
into a kind of cellular tissue. The medulla of loose hyphae passes
over to the lower cortex, also of more or less loose filaments. The outermost
cells of the latter very frequently grow out into short jagged or crenate
processes (Fig. 87).
1
Johow 1884.
Fig. 87. Cora Pavonia Fr. Vertical
section of thallus. a, upper cortex ;
b, gonidial layer; t, medulla and
lower cortex of crenate cells; d, tuft
of fertile hyphae. x 160. e, basidia
and spores x 1000 (after Johow).
2 Wainio 1890.