Introduction to Fungi, Third Edition

EUAGARICS CLADE
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Fig19.18 Basidiocarps in the euagarics clade (3): Marasmiaceae. (a) Marasmius oreades.(b)TwofairyringsofM. oreades approaching
each other on a lawn.The centres of the rings are to the top and bottom of the picture. (c) Oudemansiella radicata which grows
attached to tree stumps andburied wood andhas a long, tapering, undergroundbase to the stem (pseudorhiza). (d) Armillaria mellea.
(e) Flower cushion of cocoa tree infected by the monokaryotic mycelium of Crinipellis perniciosa.Bothhealthyflowersandswollen
infected shoots are visible. (f) Basidiocarps of C. perniciosa on a dead cocoa twig. (e) and (f) from Griffith et al.(2003),New Zealand
Journal of Botany, by copyright permission of the Royal Society of New Zealand; original images kindly provided by R.N. Birch, J.N.
Hedger and G.W.Griffith.
rings show that they can extend outwards at a
rate of about 1 3.5 cm per annum, and measurements
of their diameter indicate that some,
in permanent pastures, may be centuries old.
The mycelium is intermingled with the grass
roots usually near the soil surface at a depth of
8 10 cm, but it may extend to a depth of 30 cm,
depending on soil type. Closer inspection shows
that there are three concentric rings at the soil
surface: (1) an outer zone in which the grass is
greener and taller than outside, and in which the
fungus fruits; (2) a middle zone where the
grass is dead and the ground bare, especially in
dry seasons; and (3) an inner zone of stimulated