Introduction to Fungi, Third Edition

458 LICHENIZED FUNGI (CHIEFLY HYMENOASCOMYCETES: LECANORALES)
when placed in a windstream and that eddy
currents effectively remove soredia.
Usnic acids (Fig. 16.5) are particularly common
in Cladonia spp., and their concentration in the
lichen thallus has been shown to increase linearly
with the intensity of UV light, supporting a
possible role as a light screen (Rundel, 1969).
Further, sun-exposed thalli of Cladonia spp. appear
yellowish whereas those in more shaded habitats
are greyish-green, although the pigment responsible
is not usnic acid.
The reindeer lichen genus Cladina is closely
related to Cladonia (Stenroos & DePriest, 1998).
The most common species are C. rangiferina (Plate
8f) and C. stellaris, which are a major winter food
for grazing animals such as reindeer or caribou
in northern boreal forests (Richardson, 1988).
These lichens provide an important component
of the ground cover grazed by animals, and are
also used by Laplanders to make hay for their
animals. Reindeer lichens are popular in
Germany as decorations on wreaths and are
also well-known among model railway enthusiasts
and architects who use the highly
branched fruticose thalli as miniature trees
(Kauppi, 1979; Richardson, 1988).