Introduction to Fungi, Third Edition

EXAMPLES OF MUCORALES
189
Fig 7.2 2 Projectiles of Pilobolus (diagrammatic). (a) Sporangium with adherent drop of sporangiophore sap about to strike an
obstacle. (b) Sporangium after striking the obstacle.The sporangiophore sap has flowed round the sporangium which has turned
outwards so that the mucilage ring adheres to the surface of the obstacle (after Buller,1934). (c) Sporangiophore releasing a
sporangium. Note the jet of liquid and the bending of the narrow base of the sporangiophore under the recoil of the discharge
(after Page,1964).
as nutrients is stimulated by the addition
of thiamine, haemin and coprogen, an organoiron
compound produced by various fungi
and bacteria (Hesseltine et al., 1953; Page, 1960;
Levetin & Caroselli, 1976). Sporangium formation
is stimulated by ammonia, and in dual
cultures Mucor plumbeus may release sufficient
gaseous ammonia to induce asexual reproduction
in Pilobolus spp. (Page, 1959, 1960).
Pilaira
Pilaira (Fig. 7.23) also appears early in the
succession of coprophilous fungi, i.e. the order
in which their fruit bodies appear on herbivore
dung incubated under moist conditions. It has
not been found in the tropics (Kirk, 1993). The
structure of the melanized sporangium closely
resembles that of Pilobolus in that the spores are
separated from the columella by a mucilaginous
ring which extrudes from the base of the
sporangium. There are, however, no trophocysts
or subsporangial vesicles, and sporangial release
is non-violent. The cylindrical sporangiophores
are phototropic, and when mature, especially
under moist conditions, they elongate rapidly
to a length of several centimetres (H. J. Fletcher,
1969, 1973). Their development essentially
resembles that of Phycomyces. In a moist atmosphere,
the mucilaginous ring may absorb water
and swell considerably so that a large sporangial
drop is formed (Ingold & Zoberi, 1963). When the
mucilaginous ring at the base of the sporangium