1916] 
ZELLER—PHYSIOLOGY OF LENZITES SAEPIARIA 449 
without excess of water were inoculated and enough water 
added from time to time to keep the humidity high, but the 
mycelium did not spread far from the place of inoculation. 
Where the blocks were kept saturated until after inoculation 
the mycelium grew rapidly over the surface, no matter what 
the nature of the block. As the water evaporates the 
mycelium penetrates, and the superficial growth dries down 
and disappears. The interior of the blocks, however, holds 
moisture for a longer time than the surface, and in such a 
proportion to the wood fibre that the nearest to optimal water 
content is reserved in the interior. This is shown by examples 
of Lenzites rot wherever it is found in nature, as well as in 
pure cultures. Blocks that show a reduction in weight (due 
to decay) of from 40-60 per cent show internal decay, with 
a crust of fairly sound wood over the surface. If two blocks 
fit rather closely together during incubation the surfaces in 
contact may be decayed. 
A large series of blocks inoculated with L. saepiaria were 
kept saturated for a year, and they were reduced very little 
by the fungus. The reduction was all superficial and appeared 
as a ‘‘scorching’’ of the surface. Microscopic examination 
showed that the hyphae penetrated to a depth of but three or 
four tracheids. Plate 8, figs. 13-17, shows a series of blocks 
having this superficial ‘‘scorching,’’ and figs. 8-12 show the 
internal decay mentioned above. From these observations it 
is apparent that the oxygen requirement of L. saepiaria is 
low. A certain percentage of water is a necessary factor, 
but total saturation is injurious to the fungus because of the 
paucity of oxygen. The optimum, maximum, and minimum 
percentages of air and water have not been determined. 
From the above observations it will be seen that any factors 
influeneing the proportion of water and air are of great im- 
portance. Seasonal cracks, due to drying, of ties and other 
structural timbers afford an entrance place for the fungus 
and the necessary air, and usually the decay is found in radial 
blotches when the end of an infected timber is observed. 
(4) When coniferous trees are wounded in one way or 
another the majority of them exude pure resin from the 
