2 BULLETIN 510, U. S. DEPARTMENT OF AGRICULTURE. 
the effective control of such losses, a field study covering about seven 
months' active work was undertaken during 1914 to determine the 
conditions under which lumber and structural timbers are stored, 
for it is a well-known fact that timber infected with wood-destroying 
fungi during storage may be the direct cause of outbreaks of rot in 
buildings when such timber is placed in situations favorable to decay. 
On account of the many failures in timber in important structures 
during recent years, 1 such an investigation is of the highest impor- 
tance, both from the standpoint of owners and contractors and from 
that of the timber interests themselves. 
The writer has encountered a number of instances where he was 
informed that wood has been replaced by steel or concrete for no 
other reason than the failure of locally available timber to withstand 
decay. An increasing use of these structural materials is bound to 
occur unless the lumber industry takes steps to improve the quality 
of its product for the North American market, and the first step in 
this process of regeneration lies in the better sanitation of lumber 
storage yards, so as to remove the danger of directly transferring 
fungous infections from the lumber dealer to the consumer. 
During the course of this study a large number of sawmills and 
wholesale and retail lumberyards were visited in the eastern half 
of the United States. The region comprised 10 States along the 
Atlantic coast from Maine to Florida, all of the Gulf States, and 
the Central States of Arkansas, Iowa, Illinois, and Wisconsin. In 
addition to a personal inspection of the yards, much valuable in- 
formation was obtained directly from the operators. 
CAUSE OF DECAY IN TIMBER. 
Decay in timber is almost exclusively due to the action of fungi, 
the greater part of the destruction being referable to one of the 
higher groups of these organisms, namery, the Hymenomycetes. In 
the life cycle of these fungi there are two distinct phases of develop- 
ment: (1) The vegetative stage (mycelium) and (2) the fruiting 
stage. 
MYCELIUM. 
The mycelium consists of microscopic threadlike filaments, usually 
branched, which penetrate the wood either by traversing the natural 
longitudinal passages, such as the pores, resin canals, or cell cavities,, 
or by passing through the walls or through the pits in the walls of 
the wood fibers or tracheids (PL I, fig. 1). The mycelium also in- 
vades the pith lays, which contain a great abundance of food mate- 
1 In this connection, see the report hy F. J. Hoxie, entitled " Dry Rot in Factory Tim- 
bers," 34 p., 10 fig., Boston, 1915, published by the Inspection Department of the Asso- 
ciated Factory Mutual Fire Insurance Companies, Boston, Mass. 
