130 CHAPTER 7
Fig. 7.8Part of a wooden door post heavily rotted by
Serpula lacrymans. The surface of the timber is covered with
dense yellow/white mycelial fronds of the fungus. The wood
shows the characteristic block-like cracking (arrowheads)
typical of dry rot.
Fig. 7.9Mycelial cords and fans of hyphae produced
by a mycorrhizal fungus, Lactarius pubescens, on an agar
plate.Fig. 7.10Mycorrhizas of Basidiomycota
on a tree root. The narrow roots are
enclosed in a dense fungal sheath.Similar mycelial cords and fans of hyphae are seen
in many ectomycorrhizal fungi of forest trees (Fig. 7.9),
where they are responsible both for the spread of myc-
orrhizal development and for capturing mineral nutri-
ents and translocating them back to the root system.
The “fungal carbohydrates” are also implicated in
many plant-parasitic and symbiotic associations. The
initial studies on this were made by Harley with the
ectomycorrhizal fungi of beech trees. These fungi pro-
duce a substantial sheath of tissue around the root tips
(Fig. 7.10), and this sheath can be dissected away for
separate chemical analysis. When the leaves of tree
seedlings were exposed to^14 CO 2 , the label was found
mainly as sucrose in the leaf, stem, and root tissues,