For wood mycologists, the work of Savory (1954a,b)
marked an important step in the understanding of decay
processes by lignolytic fungi. His description of decay by
ascomycete and deuteromycete fungi in wood from
industrial water cooling towers revealed a particular
pattern observed previously by Bailey & Vestal (1937),
Tamblyn (1937) and Barghoorn & Linder (1944) in wood
from other situations. This type of decay was termed ‘soft
rot’ because of the spongy texture of the wood surface.
Soft rot, characterized by hyphal penetration of the wood
cell walls in a fashion similar to sap-stain fungi, results in
the formation of decay cavities in the central zone of wood
cell walls, which leads to their ultimate destruction. Soft
rot was therefore described as distinct from the brown and
white rot forms of wood decay normally attributed to
lignolytic basidiomycetes and some of the larger ascomycetes,
such as members of the Xylariaceae. Indeed,
members of the genera Daldinia, Hypoxylon and Xylaria
have usually been considered to be white rot fungi.
However, the boundaries between these three types of
fungal decay have since become less clear-cut and a report
in this issue, of a study into hyphal penetration of the
reaction zone in beechwood (Schwarze and Baum, pp.
129–140), identifies different penetration mechanisms.