526 
Journal of Agricultural Research 
Vol.XXIX, No. II 
may become soft and spongy and the 
remaining tissues become collapsed; 
and the result may be a stringy, spongy 
mass merging into hollow rot (fig. 1, A). 
Ring scale or ring rot may result from 
the more rapid dissolution of the cells 
in the spring wood of each annual ring, 
or a group of pits or pockets of isolated 
decayed tissues may be formed as in 
Trametes pini, Stereum frustulosum 
(Pers.) Fr., or Polyporus amarus Hedg. 
The texture of the infected wood va¬ 
ries from a soft, spongy mass to a 
shrunken, cracked mass of easily 
crushed material. 
The terms early incipient , incipient, 
and late incipient may be used for the 
early stages, and early typical, typical , 
and late typical for the later ones, al¬ 
though hard and fast lines can not be 
drawn, as the process is continuous. 
DECAY PROCESSES 
Under certain conditions wood is 
very stable. Exclusion of air from it 
by immersion in water, or by thorough 
drying and subsequent exclusion of 
moisture, prevents decomposition by 
decay. However, all wood is subject 
to decay when attacked by the right 
organism developing under favorable 
conditions. Both heart wood and sap- 
wood are attacked by wood-rotting 
fungi, the sapwood usually proving less 
resistant. Similarly, on account of its 
thinner cell walls and greater porosity 
or its different chemical composition, 
the spring wood of the annual ring 
offers less resistance to fungous attack 
than the summer wood. This often re¬ 
sults in a type of decay called ring scale 
or ring rot, in which the annual rings 
split apart in a cylindrical plane. 
The more pronounced decay proc¬ 
esses result usually in either a white 
rot, or a brown rot, and this furnishes a 
general basis for classification. In 
some rots the two processes seem to be 
combined to a certain degree and a 
brown rot results, which contains areas 
resembling a white rot. Certain stages 
of the rot caused by Echinodontium 
tinctorium E. and E. show this charac¬ 
teristic. 
Delignification apparently is the pri¬ 
mary process in many of the w T hite and 
brown rots. This results in the split¬ 
ting by enzymic action of the so-called 
lignin-cellulose compound into a lignin 
complex (composed of hadromal, conif- 
erin, and vanillin) and a cellulose com¬ 
plex (a polymer of starch). It rests 
with the particular attacking fungus 
whether the lignin complex is all or in 
part absorbed and the cellulose com¬ 
plex left (white rots) or whether the re¬ 
verse action takes place (brown rots) 
(11, 20, 28, 63). Some fungi are ca¬ 
pable of absorbing both compounds in 
varying amounts, as will be shown later. 
In some of the white rots the enzymic 
action continues and in the typical stage 
the lignin complex is often entirely re¬ 
moved, so that the presence of alde¬ 
hydes can not be demonstrated with 
the use of indicators (18). In others a 
bleaching action takes place as the rot 
develops and the typical reaction 
wherein the lignin compound is re¬ 
moved seems lacking. 
The cellulose complex is removed 
and apparently absorbed by the fungi 
producing brown rots. This cytolytic 
action usually leaves a brown, friable 
mass resembling charcoal in brittleness 
and composed mainly of the elements 
of the lignin complex. The decompo¬ 
sition may proceed by an attack upon 
the tertiary wall first and advance to 
the primary wall, or the process may be 
reversed. In these processes all stages 
from partial to complete disintegration 
of the cell walls are to be found. The 
bore holes produced by the hyphae in 
penetrating the cell walls are evidence 
of a complete localized destruction of 
the wall. 
The dissolution of the primary cell 
wall may take place before or after the 
cytolytic reaction begins. Separation 
of the two halves of the primary wall 
in the incipient stage of decay is 
characteristic of certain rots. In the 
typical stage of other rots it may 
represent the last phase. An enzyme, 
pectase or pectinase, has been described 
as the ferment responsible for this 
action in various plant tissues (20, J { 2). 
Czapek (20), discussing decay in 
wood, lists hadromase as the deligni- 
fying enzyme; cytase, the enzyme at¬ 
tacking cellulose; and pectase, the 
enzyme attacking the middle lamella 
of the cell wall. Schmitz (66) working 
with Echinodontium tinctorium E. and 
E. isolated a dozen different enzymes 
from the powdered mycelial mat de¬ 
veloped in pure culture on carrot 
media. The same writer (67) working 
with Polyporus volvatus Pk. recorded 
12 enzymes; and he listed 13 enzymes 
for Fomes igniarius (L.) Gillet. Zeller 
(91) determined the enzymes produced 
by Lenzites sepiaria growing on artificial 
media. A specific type of decay is 
thus produced in wood by a specific 
fungus; and a certain species of fungus 
produces quite similar decays in differ¬ 
ent species of woods, with occasional 
minor variations. 
