THE LARCH CANKER 19 



eventually be impossible to detect from the outside where 

 the canker has been, but though the tree is to all appear- 

 ances sound, there remains inside the blemish which the 

 canker has left. 



At present larch canker is prevalent only in Europe. It 

 has been recorded from Britain (until twenty years ago it 

 was rarely found in Ireland, but has now become common), 

 France, Holland and Belgium, Scandinavia, Russia, Ger- 

 many, Austria, Hungary, Italy and the Balkans, and 

 probably its boundaries here are coterminous with those of 

 larch cultivation. Australian and American text-books do 

 not include the disease among their own pests, but care will 

 be needed to prevent its introduction to these countries 

 with seedlings from Europe. Indeed it has already been 

 reported from Newfoundland, so that the danger to America 

 is imminent. 



Historical. It would be hard to say when or how the 

 canker fungus was first introduced to Britain. According 

 to Booth (1904) it was known to the Duke of Atholl at the 

 beginning of the nineteenth century, 1 and Loudon (1838, 

 p. 2384) quotes as follows from de Candolle : ' Sometimes, 

 also, we see the larches having a wound of resinous cancer ; 

 but this seems to proceed from some accidental cause, such 

 as a blow or a knock, which the tree may have received 

 when it was in full sap. All these observations incline me 

 to think that the cause of the diseases which attack the 

 British larches must be sought for in some difference exist- 

 ing in the physical nature or in the culture of your trees 

 and ours.' From this quotation we learn not only that the 

 canker was fairly common in Britain by 1838, but also 

 that it was less frequent in France than here. 



The suggestions offered by de Candolle on the etiology 

 of the canker are not happy, and London's volume had 

 reached the conventional age of manhood before the true 



1 I have been unable to find a copy of the Duke of Atholl's book (1832) 

 to confirm this reference. Schotte's view (1917) that ' canker, as a rule, 

 has always been found where the larch occurs ', may probably be accepted 

 for Britain as well as Sweden. 



C 2 



