THE LARCH CANKER 23 
found. Hartig noticed certain microdimensional differences 
between the canker fungus and the type Peziza calycina, 
and named the former Peziza Willkominii, but as these 
differences are not constant this name may be dropped. 
The synonomy of the fungus is difficult, and is discussed in 
a note at the end of Chapter IV. 
The most important contribution which Hartig made to 
our knowledge of the disease was the result of his experi- 
ments on artificial infection. Previous experiments of this 
sort had been carried out by Fischer, a practical forester, 
in 1877; he cut pieces of bark and phloem out of a canker 
area and fitted them into suitably-shaped holes made in 
healthy trees; the latter became infected and ultimately 
showed all the features of canker. This proved that the 
canker was due to some transmissible cause, and was not 
entirely the result of unsuitable growth-conditions, as seems 
to have been generally supposed by English foresters even 
as late as 1895! But it did not establish a connexion between 
the disease and any one fungus, since a portion of infected 
tissue cannot be regarded as a pure culture of any particular 
parasite, and, as far as Fischer’s experiments could testify, 
the Peziza might be a more or less constant concomitant of 
the canker without being its cause. 
Hartig’s experiments were of a more exact nature. He 
grew small larches one metre high in pots and infected 
them on September 29, 1879, with ascospores through small 
wounds. The pots were left in the open till the beginning 
of January, when they were placed in a room, and by the 
middle of January disease, accompanied by death of the 
bark, was noticed within a centimetre of the points of infec- 
tion. By the middle of February normal fructifications 
were formed. Investigations showed that the mycelium 
had grown in October, but rested in November and Decem- 
ber. All attempts at infection with uninjured trees failed, 
and it was only found possible to inoculate trees through 
wounds. On this rather slender evidence Hartig based his 
theory that the fungus could not gain admission to trees 
which were entirely uninjured. 
