280 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



weakened by the loss of their leaves that they are unable to obtain 

 sufficient nutriment for their sustenance. Care should be taken 

 to clear away all the needles from the seed-bed, as the spores lying 

 in the soil can play an important part in the cause and spread of 

 the disease. 



Peziza WiUkovi m ii. 



The canker of the larch disease is due to the attack of a fungus 

 known scientifically as '^Peziza Willkoinmn.^' Like all fungi, it 

 spreads by spores, which in this case are produced in cup-shaped 

 fructifications, which are always to be seen protruding from the 

 dead bark of the larch in the neighbourhood of a blister. These 

 bodies are about the size of a biggish pin-head, and when fresh are 

 of a rosy hue inside and white externally. On the spores germi- 

 nating, the mycelium enters under the bark wherever it can find 

 any damaged place. Then it spreads forth branches, so that in a 

 short time a regular network is formed, which attack and kill all 

 living cells with which they come in contact. In this way all the 

 cells of the cortex, bast, and cambium are killed, no new wood 

 being formed on that part, and if the growth of the parasite is 

 faster than the growth of cambium, the tree will undoubtedly die. 

 The outflow of resin, which is so characteristic of the disease, is due 

 to the shrinkage and cracking of the wood and tissues consequent 

 on their death. In regard to the part of the tree attacked by the 

 disease, it is generally to be seen at the base of a branch or twig, 

 and if the blister be examined, a dead branch or twig may generally 

 be seen protruding from the centre of the diseased part. If a part 

 of a tree should escape infection until it is two or three inches 

 thick, the chances are decidedly in favour of its escaping the 

 disease altogether at that particular part. The belief is that if 

 the spores of this fungus germinate on the sound bark, cortex, or 

 other part of the larch tree, the hyphse fail to effect an entrance ; 

 on the other hand, if the spores are sown on a wound, however 

 slight, the mycelial threads are able to enter and set up the disease. 



Diseases In.jurious to Hardwoods. 

 There are a few diseases which attack seedlings, which, in 

 favourable circumstances, prove disastrous to the young plants. 



Rosellinia quercina. 

 This disease attacks the roots of young oak seedlings in nursery- 

 Vjeds, and occasions fading and dying away of the plants. The 



