Dec. 1, 1924 
Diagnosis of Decay in Wood 
553 
question whether the isolated fungus, 
when placed in contact with sterilized 
sound wood under favorable condi¬ 
tions, produces a rot identical with 
that from which it was isolated. 
The one difficulty to be guarded 
against is that of contaminations. 
Contaminating fungi present in the 
sample produce mixed cultures of very 
uncertain value; and the contamina¬ 
tions incidental to the technique of 
culturing are usually due to fungi 
which either inhibit or mask the 
development of wood destroyers on the 
agar. Mention has already been made 
of the fact that the late typical stage 
of the brown rots often shows a large 
amount of mold contamination when 
cultured. For critical study such ma¬ 
terial is obviously objectionable. 
For extensive comparison of the 
color reaction produced by specific 
fungi, Long and Harsch (50) have rec¬ 
ommended various media, but in 
routine commercial diagnosis the use 
of 8 or 10 different media is imprac¬ 
ticable. Plain malt agar slanted in 
tubes has been found a very satisfac¬ 
tory standard medium in the present 
cultural work. 
ARTIFICIAL PRODUCTION OF TYPICAL 
DECAYS 
White (89) has noted the fact that 
there appears to be one general weak¬ 
ness in method throughout the works 
on forest pathology. This weakness 
is the identification of causal agents of 
wood rots based almost entirely upon 
the more or less constant association 
of the fungus with the rotted wood. 
In plant pathological investigations 
and in all standard bacteriological re¬ 
search Koch's rules are applied in their 
entirety in order thoroughly to estab¬ 
lish the relationship between the causal 
organism and the symptoms. The 
comparison between bacteriological 
technique and organisms involved and 
the technique and organisms involved 
in wood-rot studies can not be drawn 
too closely. However, in the study of 
wood rots only the first rule, that of 
constant association of the organism 
with the disease, has been applied with 
any degree of consistency. It is equally 
important to establish with precision 
the relation between cause and effect 
in the study of wood rots as it is in the 
study of other plant diseases. The 
fact that more than one organism may 
be found developing simultaneously 
in the same substratum is sufficient 
ground for establishing a more accurate 
test for the identification of a wood- 
destroying organism with the particu¬ 
lar type of decomposition produced in 
wood. 
Only a few of the papers examined 
give cultural data showing the rela¬ 
tionship between fungus and wood rot. 
Of these, only the work on Forms ap~ 
planatus by White (89) indicates inten¬ 
tional application of the rules of proof. 
He inoculated basswood, poplar, pine, 
spruce, tamarack, hemlock, fir, cedars, 
maple, and willow blocks with pure 
cultures of Forms applanatus and 
secured typical rots in all but the 
conifers, where slight infection only 
was noted. Typical sporophores shed¬ 
ding mature spores were produced. 
Abbott (1) secured the typical decay 
caused by Trametes pini in tamarack, 
pine, hemlock, spruce, balsam, birch, 
and oak by inoculation with pure cul¬ 
tures of the organism. The above 
order of the hosts, according to Abbott, 
is the order of susceptibility to the 
fungus. 
Bayliss (4) produced the typical rot 
caused by Polystictus versicolor Fr. by 
inoculating various hardwoods with 
pure cultures of this organism. Typical 
sporophores were also produced, partly 
under natural conditions, on the in¬ 
fected blocks. Infection was not se¬ 
cured in the wood of pine and larch. 
Zeller (92) used Lenzites sepiaria to 
inoculate blocks of southern yellow pine 
for durability tests and noted that the 
typical rot was produced in all cases. 
The writer has produced incipient 
and typical decay with a number of 
wood-rotting fungi developing under 
artificial conditions. The following 
method was used in conducting these 
experiments: 
(1) Numerous field observations (ex¬ 
tending over several years) were as¬ 
sembled to check the constant associa¬ 
tion of the organism with the particular 
wood rot in the typical stage. (2) 
The organism was isolated from the 
decayed wood and pure cultures estab¬ 
lished, using fragments of decayed 
wood, sporophore tissue, and spores. 
(3) Sound sterilized wood was inocu¬ 
lated with pure culture inoculum, to 
prove that the organism can produce 
the incipient and typical stages of 
decay. (4) The organism was reiso¬ 
lated from the inoculated wood and 
compared with the original pure cul¬ 
tures or stock cultures, or with both. 
In the isolation of the organism from 
the piece of rotted wood 10 to 12 tubes 
were prepared from each wood sample 
(fig. 3, A). The fragments were 
selected from various areas on the 
surface representing both incipient and 
typical stages of decay. Subcultures 
were then made from these original cul¬ 
tures. Two sizes of sound wood pieces 
were used, each an inch square, the 
one being 5inches long, the other 11 
