228 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



by the shading of the upper branches, but this method is less 

 important since it only affects trees which are being killed out 

 through lack of light. The importance of wounds in connection 

 with infection is considered to have been over-estimated by 

 previous investigators. The author, therefore, suggests a method 

 of prevention of canker by the removal of dead branches in 

 plantations from six to eighteen years old t but, as pointed out, 

 this would prove very expensive, and there is little doubt that 

 in a large number of cases it would be impracticable. 



A detailed description of heart-rot caused by Pomes annosus 

 is given, dealing especially with the secretions of the fungus and 

 the decomposition of the wood. Cultures on artificial media 

 and on soil are described, and the results of a number of 

 infection experiments are given. The frequency of heart-rot in 

 plantations forming a first rotation on old agricultural soil is 

 discussed. The author considers that the methods of infection 

 suggested by Hartig — by spores and by means of diseased roots 

 coming into contact with healthy ones — are inadequate, and 

 suggests that infection through dead roots is, in many cases, 

 the cause of the disease. Isolation of diseased trees by trench- 

 ing is not recommended as a general means of prevention on 

 account of the labour involved, and also because of the fact 

 that this method does not prevent the distribution by air of 

 conidia produced on the sides of the trench. Heart-rot caused 

 by various other fungi is also described. 



Leaf diseases of the larch are comparatively infrequent in 

 Britain, and the two caused by rust fungi are probably the 

 most widespread. In describing the leaf blister rust the 

 author takes it for granted that this is the aecidial stage of 

 Melampsoridium betulinum, and the experiments carried out by 

 Plowright give very considerable support to this conclusion. 

 The wide distribution of the disease on the birch and its rarity 

 on the larch, as well as the large number of specialised forms 

 known to exist in closely allied genera, however, suggest caution 

 in drawing a general conclusion of this kind. In the case of the 

 specimens of Peridermium laricis obtained from Inverness-shire, 

 no infection experiments have yet been carried out on the birch, 

 and until these have been successfully performed the retention 

 of the name Peridermium laricis is advisable. 



Mr Hiley is to be congratulated on his book, which not only 

 brings together the work carried out by previous investigators 

 on the diseases of the larch, but contains a considerable number 



