1921-22 



DEPARTMENT OF LANDS AND FORESTS 



265 



fungus, ascribe to it a decay in the outer sapwood immediately under the bark, 

 from there working inwards. An examination of hundreds of affected trees 

 has failed to substantiate this view in any one instance. On the contrary, in 

 living trees, the fungus enters through wounds or broken or dead branch stubs 

 and penetrates to the inner sapwood and heartwood, rapidly spreading up and 

 down in these regions of the stem and more slowly outward towards the bark. 

 Figure 2 illustrates a section taken from a living beech in which this fungus is 

 working as a pure heart rot. In birch it appears to spread more abundantly 



Photographs by Hedgcock & Hunt. 



Fig. 4. — Cankers in Lombardy Poplar caused by Dothichiza populea. 



i 



and rapidly in the inner sapwood as is shown in Figure 3, but it is important 

 to note that the adjoining heartwood is also affected and, in consequence, weak- 

 ened. One of the most significant features is the circumstance that cured 

 timber from trees in which the decay is in its incipient stages, is indistinguish- 

 able by ordinary means of examination at the command of the user, from per- 

 fectly sound timber. The infection of the birch appears to be commonly as- 

 sociated with the breaking of the branches of the crown, due to the action of 

 a boring insect. Complete results will be published when the investigations 

 have been brought to a conclusion. 



