6 BULLETIN 1298, U. S. DEPAETMENT OF AGEICULTUEE 
film of water on the wood surfaces, lie believes, is highly favorable 
to germination. Just what moisture content of wood is most favor- 
able to decay after infection has once taken place is not known. Nor 
is it known what moisture is necessary for infection of sound wood 
from an infected stick lying in contact with it, so that the mycelium 
may grow from the one to the other. The study of this phase of the 
problem is complicated by the fact that moisture may possibly be 
added to the wood by direct secretion from the mycelium ana by 
the breaking down of the wood substance itself, in which process 
water is one of the products formed. Decay may therefore appear 
in certain cases, to take place somewhat below fiber saturation. 
A certain amount of air in the wood is absolutely necessary for the 
occurrence of decay. The fungi require it in their growth. When 
the wood is saturated, the air in the wood cells is displaced by water, 
and fungous growth and decay are impossible. 
The fungi which decay pulpwood generally grow best at temper- 
atures between 75 and 95° F. All will grow at much lower temper- 
atures, but much more slowly. The most severe winter conditions 
do not kill them. They merely cease growing and remain dormant. 
On the other hand, a rise of temperature of but a few degrees above 
the optimum has a greater retarding influence on growth than a cor- 
responding reduction. The conditions of moisture and temperature 
under which fungi thrive are such that in most pulp-wood regions 
they will find a favorable environment during the greater part of 
the year. 
FUNGI THAT DECAY STORED PULP WOOD 
The fungi which have been found causing extensive decay in stored 
pulp wood in the regions investigated are: Polystictus Mrsutus (PI. I, 
fig. 4) ; Polystictus versicolor, Polyporus adustus (PL II, figs. 3 and 4) ; 
Stereum purgureum (PI. II, fig. 6) ; Fomes roseus (PI. I, fig. 5) ; 
Lenzites sepiaria (PL I, fig. 6) ; Polystictus abietinus (PL II, 
figs. 1 and 2) ; Stereum sanguinolentum (PL II, fig. 5) ; and Trametes 
pini. The first four species mentioned attack hardwoods; the first 
three are particularly prevalent on aspen. The other fungi attack 
conifers. Other fungi found only occasionally are Fomes 'pinicola, 
Lenzites trabea, Trametes JieteromorpTia, Tr. peckii, Pleurotus ostreatus, 
Schizofhyllum commune, Corticium galactinum, Stereum rugosiusculum, 
and Hypoxylon cohaerens. Many others are undoubtedly present, 
particularly in the southern and western regions. In Sweden (15) 
Corticium evolvens is reported as doing considerable damage to spruce. 
Those producing heart rot in living trees are Fomes roseus, Fomes 
pinicola, and Trametes fini in conifers, and Pleurotus ostreatus in 
hardwoods. Trametes pini produces the so-called "red heart, "or 
< c ring scale." 
STORAGE OF PULP WOOD 
CHARACTER OF WOOD AVAILABLE FOR PULPING 
The principal woods used for pulping are: Spruce, 57 per cent; 
hemlock, 14.5 per cent; aspen, 6 per cent; balsam fir, 5.4 per cent ; and 
various yellow pines, 5.3 per cent. Other woods used in smaller 
quantities are jack pine, white pine, white fir, tamarack, basswood, 
beech, birch, cottonwood, gum, maple, and yellow poplar. 
