74 College of Forestry 
In the case of attempts to infect sterile blocks of wood by 
inoculation with spores, both germinated and ungerminated, 
it was noticed that the resulting infection and spread of the 
mycelium was either very slow or failed altogether. Evi- 
dently there are some conditions for the ready development 
and spread of the mycelium in wood under natural environ- 
ment that are difficult to duplicate by artificial means. 
Otherwise wood would not be attacked so readily in nature. 
A far easier and more reliable means of infecting blocks of 
wood was found in the method of placing in contact with 
them a piece of decayed wood containing active mycelium. 
Upon examination of some successful infections, at the begin- 
ning of the appearance of the mycelium, it was found that 
the mycelium had partially broken up into oidia before any 
considerable mycelial growth had been made. Learn (1912, 
p. 544) observed tint oidia were present in cultures of 
Pleurotus ostreatus Jacqu. on blocks of wood and that new 
growths arose at the base of these blocks, apparently due to 
the shedding of the oidia from above. It is not improbable 
that in nature the formation of this secondary spore form 
may be a useful and additional means of propagation. 
The growth of the mycelium on inoculated blocks of sterile 
wood always gave uniform results. In both methods of 
inoculation (by the use of germinated basidiospores and by 
contact inoculation by pieces of infected wood) the mycelium 
spread over the surface of the wood in the form of irregularly 
running, white mycelial strands of varying (hide, 
(Plate XII, Fig. 1.) A microscopic examination of these 
strands showed that they were composed of smaller strands 
of hyphze which had anastomosed irregularly to form the 
larger strands. The smaller strands of hyphee were com- 
posed of. varying numbers of colorless hyphee which were 
fused together in a highly irregular manner. The individual 
hy phee exhibited a large number of cross-walls and clamp 
connections and innumerable branching of an exceedingly 
irregular character. As the strands of hyphze spread over the 
surface of the blocks, they gave rise to more or less rounded, 
compact masses of mycelium (Plate XII, Fig. 1), but the 
