THE LARCH CANKER 25 
chiefly through his untiring zeal that chaos has given place 
to order. The authority of Hartig’s name had become so 
grcat that it has been thought scarcely worth ‘while to 
reinvestigate diseases on which he had written, and con- 
sequently less is often known about parasites which he 
investigated than about others, of smaller importance, 
which were unknown in his time. The ground has been left 
as Hartig tilled it, and pathologists have sought new fields 
where the spirit of the pioneer hay attracted them. Hartig’s 
views were presented in English by Marshall Ward (1889), 
but without addition or correction. 
Among subsequent papers the following may here be 
noticed : 
Carruthers (1891) noted the blackening of the bark in the 
neighbourhood of the canker, which he attributed to the 
fungus Antennaria pithyophila, Fr., which looks like a covering 
of soot. As the result of observations on young cankered trees 
which showed no sign of having becn wounded, he expressed 
the opinion that young trees might be attacked by the Dasy- 
scypha while still unwounded, if the bark and air were damp. 
Somerville (1895) published the results of an inquiry 
among foresters, instituted by the English Arboricultural 
Society, in pursuance of which a number of questions were 
put in relation to the causes and nature of larch canker. 
Forty answers were received, the chief value of which was 
to elicit evidence as to the kinds of soil and climate in 
which the disease was most to be feared. The majority 
agreed that damp situations arc favourable to the canker, 
and many regarded larch aphis as a predisposing factor. 
Somerville suggests that this is due to the partial inhibition 
of transpiration caused by the aphis, and also that the 
aphis makes holes in the twigs and spurs, through which 
the spores of Dasyscypha may infect. A similar inquiry 
was held by the Scottish Society in 1905 (vide Richardson, 
Borthwick, and Mackenzie). 
Massee (1902) performed experiments to demonstrate the 
connexion between the aphis, Chermes abietis, and the entry 
of the Dasyscypha, and found that canker spots resulted 
