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 

 great 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 has 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 pithy ophila, FT., which looks like a covering 

 of soot. As the result of observations on young cankered trees 

 which showed no sign of having been wounded, he expressed 

 the opinion that young trees might be attacked by the Dasy- 

 scypJia while still un wounded, 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 arid climate in 

 which the disease was most to be feared. The majority 

 agreed that damp situations are 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 



