PDF - CES (IISc)

STRUCTURES PECULIAR TO LICHENS 127
b. DEVELOPMENT OF CYPHELLAE. The cortex of both surfaces in the
thallus of Sticta is a several-layered plectenchyma of thick-walled closely
Fig. 72. Lobaria pulnionaria Hoffm. Showing pitted surface, a, under surface.
Reduced (S. H., Photo.}.
packed cells, the outer layer growing out into hairs on the under surface of
most of the species. Where either cyphellae or pseudocyphellae occur, a
more or less open channel is formed between the exterior and the internal
tissues of the lichen. In the case of the cyphellae, the medullary hyphae
which line the cup are divided into short roundish cells with comparatively
thin -walls (Fig. 73). They form a tissue sharply differentiated from the
Fig. 73. Sticta damaecornis Nyl. Transverse section
of thallus with cyphella x 100.
loose hyphae that occupy the medulla. The rounded cells tend to lie in
vertical rows, though the arrangement in fully formed cyphellae is generally