THE HONEY FUNGUS 161 
covered by resin, they are only open to infection for a very 
short period. 
Evidence from observation confirms the deduction that 
infection by spores is unusual, for when attacked trees are 
rooted up it is almost always found that the soil in their 
vicinity is infested with rhizomorphs, which can generally 
be traced to a neighbouring stump. In such cases the 
evidence for infection by rhizomorphs as against infection 
by spores is overwhelming. 
What then is the use of spores? Spores are the common 
means by which the fungus attacks dead, but uninfected, 
stumps. As will be shown later, a stump is employed as 
a base from which the fungus attacks living trees, so that 
spores are the medium by which it forms new bases from 
which the fungus proceeds on a career of penetration in 
limited tracts of forest. , 
Infection by rhizomorphs, on the other hand, is a matter 
of common observation, and it is no doubt the géneral 
means employed by the fungus in attacking living trees. It 
is through the rootstocks or larger roots that the rhizo- 
morphs enter, but it is still a question whether an entrance 
is effected (i) through healthy, uninjured bark, (ii) through 
wounds, or (iii) through dead roots. 
Most of the experimental evidence bearing on the subject 
of infection by rhizomorphs is concerned with broad-leaved 
trees. Hartig (1894 and 1901) experimented on the oak 
and Cieslar (1896) used a variety of dicotyledons. Wagner 
(1899) planted 43 small trees of various broad-leaved species 
in a garden in which the soil was infected with rhizomorphs. 
Of these, 17 had been intentionally wounded on roots or 
rootstocks. Eight of the wounded trees became infected 
and none of the unwounded. This result is in general 
agreement with the conclusions of the other authors. 
A better known experiment of Brefeld’s, designed to 
show that Rhizomorpha subterranea could give rise to 
Rh. subcorticalis, should also be mentioned. It was 
not intended to demonstrate any pathological principle, 
so that for the present purpose it is of very limited value. 
1888 M 
