136 PROTECTION OF WOODS AGAINST 



Polyporus sulphureus. 



This fungus causes red-rot in the timber of oak, sweet 



chestnut, poplars, willows, alder, birch, fruit trees, larch and 



silver fir. Infection occurs through 

 wounds on the branches and on the 

 stems ; the timber attacked becomes 

 reddish brown, cracked and dry. The 

 mycelium spreads through the cracks 

 and forms large felted white sheets. 

 The fructifications appear annually, 

 and are very conspicuous, being large, 

 bright yellow, smooth and cheese- 

 like. 



The only remedial measure is to 

 cut down infected trees, care being 

 taken not to damage other trees in 

 removing them. Other forms of 

 Polyporus, which often have bracket- 

 like fructifications, cause various 

 forms of rot in different species. 



Nectria ditissima. The canker of 

 broad-leaved trees. 



This fungus is a very common 

 one on beech, oak, ash, hornbeam, 

 hazel, alder, lime, cherry, and apple, 

 but is chiefly found on beech and 

 ash. The part infected becomes 

 cankered, and on careful examina- 

 tion in spring, dark red globular fruc- 

 tifications will be found on it. Trees 

 of all ages are attacked, and the parts 

 infected often become greatly mal- 

 formed. Beech timber turns brown, and ash timber black, and, 

 if badly attacked, the wood is only fit for fuel. The fungus is 



Fig. 13. Nectria ditissi- 

 ma, Tul., on a beech, a Com- 

 mencement of the disease, 

 which has proceeded deeper 

 into the wood at b. 



