The Canlcer of the Larch. 
301 
of Britain as the cause of tlie disease. The microscopic fungus 
found on the diseased parts was in his opinion not the cause of 
the disease, but a result of it. 
The observations and views of foresters and others who are 
practically acquainted with the cultivation of the larch unfor- 
tunately lose much of their value because the writers have insuf- 
ficient knowledge of the nature of parasitic fungi and the effects 
they produce on their host plants. 
The real cause of the canker was not detected till 1859, 
when the late Sir W. C. Trevelyan called the attention of Dr. 
Lindley, as editor of the Gardeners'' Cliroiiide^ to his discovery 
of a small fungus associated with the disease, and forwarded 
specimens to him. Dr. Lindley submitted the letter and speci- 
mens to the Rev. M. J. Berkeley, the distinguished fungologist, 
who perceiving the imiDortance of the obsei'vation, after corre-. 
spondence with Sir W. C. Tre^•elyan, dealt with it in the Gar- 
deners' Chronicle for December 17, 1859. SirW. C. Trevelyan's 
letters (which, in view of the lack of knowledge on the subject 
at the time they were written, give a singidarly accurate account 
of the disease), have, with the rest of Berkeley's scientific corre- 
spondence, recently been acquired by the Botanical Department 
of the Bi'itish Museum. 
Mr. Berkeley, influenced by the notion generally prevailing 
at that time, that there existed a connection between the rot in 
the centre of the stem and the canker in the bark, endeavoured 
to trace the roots (mycelium) of the fungus, passing through 
the wood from the centre outwards, but without success. 
This decay, sometimes called foxing,"' produces first a slight 
discoloration of the wood in the centre of the stem, which 
progresses until the wood becomes soft and spongy, and ulti- 
mately completely destroyed, producing a hollow base to the 
stem. The process is one of simple decay in the wood, which 
begins at the base of the tree and gradually extends upwards. It 
is generally attributed to a superabundance of water in the soil, 
but is probably due to the decay of the original tap-root, which pene- 
trates only a little way into the soil before its growth is arrested, 
while the secondary roots spread out laterally to obtain the food 
necessary for the tree. This original tap-root, being no longer 
an active organ in the life of the plant, is more liable to perish, 
and would influence in its decay the centre of the stem with 
which it was vitally connected. Proper draining would be of 
great help in preventing this wet-rot attacking the root and 
stem. 
In 1855 the association of the canker with the fungus wa3 
observed by a forester in Hesse, whose report in November of 
