50 BULLETIN 1298, U. S. DEPARTMENT OF AGRICULTURE 
yields of screened sulphite pulp were not, as a rule, much lower 
than the yield from sound spruce. These yields, however, being 
figured on an oven-dry weight basis for both the wood and the pulp, 
do not represent the actual loss. If the yields per cord could have 
been determined, a distinct lowering with increased decay would 
have been demonstrated Soda cooks required more chemical for 
decayed wood than for sound, since the portion that had decayed 
was more readily soluble in the cooking liquor. When the pulp was 
undercooked, screenings were about 17 per cent, with a yield ot only 
32 per cent. In these experiments the chemical pulps from decayed 
woods were lower in strength, showed less endurance against folding, 
and were exceptionally dirty. 
Chemical analyses of various sound and decayed woods explain 
the losses that occur through decay. The principal changes are 
marked increases in constituents soluble in hot ana cold water and 
in alkali, indicating changes in the character of the cellulose from a 
resistant to a less stable form. The lignin does not appear to be 
destroyed in any appreciable amount. In the case of pulp (spruce, 
sulphite) made from decayed wood, decay is likewise reflected in 
increased solubility in water and NaOH and lessened stability of the 
cellulose. It is thus evident that a qualitative parallelism exists 
between decayed wood and the mechanical and sulphite pulps made 
from it. 
In present commercial practice pulp is usually stored in large 
piles in the open or placed in closed unheated sheds or in the base- 
ments of mills. As a result of manufacturing conditions, ground 
wood is frequently stored for 6 to 12 months, or even longer. Chemi- 
cal pulps are, for the greater part, converted immediately, or within 
a few months. Deterioration during storage is often severe, partic- 
ularly with ground wood, and is due both to molds and to wood- 
destroying fungi. Molds, though not affecting the strength of the 
pulp, discolor it and frequently bind together the pulp particles so 
that the molded spots or areas do not beat up well, and a lumpy, 
speckled paper results. Wood destroyers decrease the strength of 
the wood fibers and render them so brittle that they break into short 
lengths in the beater, with the result that much of the pulp is lost 
in the white water and the manufactured paper has little strength. 
The combined action of molds and wood-destroying fungi thus results 
in the production of paper of very poor color and quality. 
In order to combat deterioration of pulp during storage, careful 
attention must be given to the elimination of sources of infection. 
Pulp may become infected with molds either through the spores which 
abound in the air and in the water used in manufacturing processes, 
or by direct contact of moldy with clean pulp. Infection by wood 
destroyers more often occurs through contact with infected pulp or 
wood, but it may also occur through secondary spores produced 
on the fungus mycelium, or through spores of the more common 
type, produced on the fruit bodies which develop on wood in the 
form of conchs, brackets, toadstools, mushrooms, leathery incrusta- 
tions, etc. Humus soil also appears to be an important source of 
infection for both molds and wood-destroying fungi. This may be 
carried about on the workmen's clothing or shoes. 
The physical characteristics of pulp which has decayed in storage 
are similar to those of pulp made from badly decayed wood. Such 
