^] 



"CANKER" THE LARCH DISEASE 



233 



destioyed, the general effect is eventually to "ring" 

 the tree. 



To understand these symptoms better, it is 

 necessary to examine the diseased patch more 

 closely in its various stages. The micioscope shows 

 that the dead and dying cortex, cambium, and 



Fig. 35 — Porti n of stem of a j oung larch affcrttd u ith the larch disease as indicated 

 by the dead " cancerous " patch of cracked cortes a at ^nd near the margins of 

 the patch are the small cup-like fructifications of Ptziza Willkoinmii (Htg ), )\hich 

 «;pnns frcn mj celium in the dead and dying corte\ and cambium beneath (After 

 Hess ) 



young wood in a small patch, contain the mycelium 

 of the fungus which gives rise to the cup-like 

 fructifications — Peztza Wtllkommii — above referred 

 to (Fig. 3S) ; and it has been proved that, if the 

 spores of this Pezzza are introduced into the cortex 



