mechanical injury. The extensive ravages of the budworm in the 
spruce and balsam forests, for example, have resulted in the death of 
more than 40 per cent of these important pulp-wood species in the 
areas affected. Trees weakened or killed by this pest quickly show 
signs of rot. 
Investigations thus become necessary to determine to what extent 
deterioration can proceed before the wood loses its economic value 
for pulping. Such investigations are under way at the Forest 
Products Laboratory, * and it is hoped that the results will lead to 
better methods of selecting the wood, to the end that the value of 
partially decayed material will be fully realized. 
In connection with the control of decay and molding in pulp stored 
commercially, much attention has been devoted to the use of anti- 
septics introduced into the pulp to prevent the development of 
fungous growth. This was found necessary since no other remedy 
seemed at all feasible. During the progress of the investigation a 
brief report of the behavior of some of the most effective antiseptics 
and of the method of their application was distributed to the industry 
through the courtesy of the American Paper and Pulp Association. 
As there are many fungi concerned in the deterioration of both 
pulp wood and stored pulp, it was necessary to determine which of 
these were the more detrimental. For this reason a large number of 
fungi were studied individually in pure culture in order to determine 
their action on wood fiber, and the resultant infected pulps were 
examined both chemically and physically with the same object in 
view. This investigation will be continued and expanded to include 
other fungi which produce rots of distinctive types prevalent in pulp- 
wood species. 
DECAY OF WOOD 
Decay in wood is produced by fungi. These fungi are plants, 
differing from the ordinary green plants merely in their form, lack 
of green coloring matter, and methods of nutrition. Ordinary plants 
get their nutriment from the soil and air; wood-destroying fungi 
utilize wood substance for this purpose. 
Many fungi are wood inhabiting, but not all are wood destroying. 
In studying the effect of fungi on pulpwood and pulp it is necessary 
to chscriminate between two broad groups of fungi — namely, molds 
and wood destroyers. Molds are abundant on pulp, particularly 
ground wood, but play so little part in the actual disintegration of 
wood fiber that their effect on its strength may be ignored. The 
active wood-destroying organisms are for the most part hymeno- 
mycetes, or fungi comparatively high in the scale of development. 
These fungi feed actively on the wood substance. 
In the life cycle of wood-inhabiting fungi two essential stages of 
development are recognized: (1) The mycelial, or vegetative stage, 
during which the fine, cotton-like branched threads (the mycelium) 
of the fungus penetrate the wood and also develop on the surface if 
the surrounding air be moist; and (2) the fruiting stage, during which 
spores are produced for the further propagation of the fungus. 
The mycelium (PL I, fig. 1) is the absorbing system of the fungus, 
and in function is comparable to the root system of ordinary green 
plants. In the case of molds, the mycelium enters chiefly the ducts 
or medullary rays of the wood, where it feeds on the starches, sugars, 
