540 
Vol. XXIX, No. 11 
Journal o f Agricultural Research 
hyphae in infected wood has been used 
with some success in commercial work 
(88). Other useful stains (requiring 
longer preparation of the slides) have 
been developed by Sinnott and Bailey 
(75) and by Diemer and Gerry (21). 
EXTENT OF HYPHAE IN AND BEYOND 
DISCOLORED AREAS 
There seems to be very little his¬ 
tological and no cultural evidence in 
literature that the hyphae of certain 
wood-inhabiting fungi extend in and 
beyond the invasion discolorations. 
Meinecke (54, p■ 28) states that the 
incipient stage of rot due to Echinodon- 
tium tinctorium has a sound appearance 
but “has only recently been invaded 
by the mycelium.” He terms the in¬ 
vading hyphae “pioneer hyphae.” 
Boyce (8) in describing the hyphae 
of Polyporus amarus in infected incense 
cedar (Libocedrus decurrens) states 
that— 
hyphae were commonly present in the apparently 
sound wood surrounding young pockets to a dis¬ 
tance of 4 mm. (0.157 inch) and sparingly from that 
point to 8 mm. (0.314 inch) in a horizontal direc¬ 
tion.” Inf the case of the last (highest) pocket in 
a diseased tree the hyphae were abundant to a dis¬ 
tance of 1.5 cm. (0.6 inch above the pocket) and 
sparingly from that point on to 7.8 cm. (3.07 inches), 
where they ended 
Hiley (85, p. 88) in discussing the 
incipient rot produced by Fomes an- 
nosus in larch wood states that “stray 
hyphae were often found in' the red rot 
region, and where hyphae could not be 
seen, the occurrence of the empty bore 
holes proved that they had formerly 
been present. Hyphae were even seen 
in the normal colored wood outside the 
turpentine region (bordering incipient 
decay and infiltrated with resin). 
White (89, p. 156) states that the 
brown invasion zone noted in living 
trees attacked by Fomes applanatus 
“keeps pace with the advancing 
hyphae.” This would imply hyphae 
present in this zone. 
Schrenk (68) describing the mycelium 
of Polyporus juniperinus in red cedar 
(Juniperus barbadensis) states that 
the mycelium of the fungus is found in the wood 
between the holes (rot pockets), as well as in the 
sound (?) wood around the cavities, 
and of Polyporus carneus Nees, he says 
the wood between the pockets has many hyphae, 
which pass from one pocket to another. 
In his paper on the rot caused 
in white ash, Fraxinus americana L., 
by Polyporus fraxinophilus Pk. (71) 
he finds that “the first hyphae are 
generally several rings” back from the 
outer edge of the invasion discoloration 
areas. Rhoads (64) found hyphae in the 
brown discolored wood (incipient rot) 
of Lupinus arboreus Sims, produced by 
Polyporus ostreatus (Jacq.) Que’l. and 
Collybia velutipes (Curt.) Que’l. 
Munch (58) found hyphae of Stereum 
purpureum ahead of the brown inva¬ 
sion zone in infected poplar. 
Boyce (9) in a recent publication 
states that “Apparently mycelium 
does not occur in the brown discolored 
wood in advance of the white spots” in 
the rot produced by Fomes fraxinophilus 
(Pk.) Sacc. He also states that hyphae 
are not found in the brown invasion 
zone of the rot produced by Fomes 
igniarius. 
Kauffman and Kerber (48) find 
hyphae and evidence of fungous attack 
in the apparently sound wood of 
Robinia pseudo-acacia attacked by 
(Trametes robiniophila) (Polyporus ro- 
biniophilus (Murr.) Lloyd). 
Microscopical examinations.— 
The extent to which the hyphae ad¬ 
vance in and beyond the discolored 
areas of incipient rot, is shown by 
microscopical examinations, and is given 
in Table II. 
Evidently, in certain rots the wood 
apparently sound for some distance 
beyond the edge of the discolored areas 
contains abundant hyphae. The face 
of the railroad tie section shown in 
Figure 3, A, when tested by culturing 
gave positive results from the greater 
part of the area which appeared entirely 
normal in texture and color. In a Picea 
sitchensis trunk split, open for study the 
yellow spires, wdiich indicate the 
farthest limit of the incipient stage of 
rot, extended up in the trunk 5 feet 
beyond the last signs of typical rot and 
for 30 inches beyond the last brownish 
discoloration. Hyphae were observed 
in a sample taken from the yellow 
spires 25 inches beyond the last faint 
brownish-colored areas. The hyphae 
of Polyporus balsameus in Abies bal- 
samea are very numerous in the normal 
appearing wood several inches beyond 
the edge of the typical rot area (fig. 3 
E). A somewhat similar condition is 
observed for Trametes carnea and Len- 
zites sepiaria in Picea canadensis. The 
longitudinal extent of the hyphae of 
these fungi beyond the discolored areas 
has not yet been satisfactorily worked 
out. The invasion zone of Fomes 
igniarius in Populus tremuloides shows 
hyphae present, although not in large 
numbers (fig. 3, B). In some collec¬ 
tions of this rot showing a faint yellow 
area bordering the invasion zone 
hyphae are rarely found, and cultures 
from this region are usually negative. 
It is not known whether the hyphae are 
present and are merely difficult to dis¬ 
tinguish or whether the discoloration 
has preceded the hyphae. 
