CHAPTER II 
THE LARCH CANKER 
General. Historical. The mycelium of Dasyscypha calycina and its 
effect on the tissues. The canker as a pathological structure. 
General. The canker or blister of the larch is by far the 
best known of the diseases of this tree. It is exceedingly 
common and very destructive, and, since none of the methods 
which have been adopted with a view to preventing attack 
have met with success, the pest bids fair to become even 
more disastrous in the future than it has been in the past. 
In Germany it has already made larch growing so un- 
profitable that the tree has almost ceased to be planted 
except where sparingly. mixed with other species, and a like 
fate must follow it in many parts of Britain unless a system 
of growing can be adopted which will to some extent obviate 
the evil. 
The disease is due to a fungus which has been called by 
a variety of names, but is now generally known as Dasyscypha 
calycina' in Britain and D. Willkommii on the Continent. 
This fungus belongs to the class Ascomycetes, since it bears 
its spores in eights inside an enlarged hypha or ascus 
(fig. 18, a, p. 40), and it is placed in the sub-class Dis- 
comycetes since its fructification is in the form of an open 
cup or apothecium (fig. 17, p. 38), which is lined on the 
upper concave side by the asci arranged at right angles to 
the surface. 
D. calycina is almost universal on recently dead branches 
of larch trees. Its fructifications are very small, being 
seldom more than one-eighth of an inch in diameter, of bright 
orange or yellow colour above and white below, and each 
1 The synonymy of Dasyscypha calycina is discussed in a note at the 
end of Chapter IV. 
