Introduction to Fungi, Third Edition

544 HOMOBASIDIOMYCETES
Fig19.17 Schizophyllum commune. (a) V.S. portion of
basidiocarp showing the divided inrolled ‘gills’.
(b) High-power drawing of part of the‘gill’ in the
region of the split (arrowed). Note that the hyphae
in this region are thin-walled in contrast to the
thicker-walled hyphae making up the rest of the
flesh.
include genetics (Raper & Hoffman, 1974),
nuclear migration (Snider, 1965) and morphogenesis
(Wessels, 1993b, 1994). Dikaryotic mycelia
fruit readily in culture. Monokaryotic fruiting
may also occur (for references see Moore, 1998).
The early stages of basidiocarp development have
been studied by Raudaskoski and Viitanen (1982)
and Raudaskoski and Vauras (1982). A short
exposure to light and good aeration are necessary
to induce sporulation; elevated CO 2 concentrations
are inhibitory. Under dark conditions,
mycelial growth is depressed beneath the surface
of the medium under a layer of slimy material.
Within 3 h after transfer of 3 day old dark-grown
cultures to continuous light, there is abundant
growth of aerial hyphae at the margin of the
culture. After 9 h the emergent aerial hyphae
become aggregated into a horseshoe-shaped
structure which is the ventral surface of the
fruit body. After 15 h basidial initials form the
beginnings of the hymenium which develops
over the entire lower surface of the basidiocarp.
The outside of the fruit body consists of vertical
and horizontal hyphal strands, and its outermost
layer is formed by parallel backward growth of
numerous hyphal tips towards the developing
hymenium. By more rapid growth on one side,
the fruit body may become fan-shaped. The split
gills arise by marginal proliferation, and their
number is increased by downgrowths from the