14 ADDRESS BY THE PRESIDENT, NOVEMEER 3, 1875. 



The liability of tlie plant to the development of epidemic disease 

 is produced by the state of the atmosphere as regards moisture, 

 the prevalence of hot or cold weather, the amount of light, and 

 probably the electrical condition of the air and earth. The natural 

 decay of plants also renders them liable to attacks of fungi, etc. 

 Thus leaves, before they fall, are often affected. The trunk and 

 branches of a tree become most frequently gangrenous when they 

 have attained maturity. Most epidemic diseases may be averted 

 by keeping plants properly exposed to light, ah, and moisture. 



The influence of the sea breeze, carrying with it saline matter, 

 is prejudicial to most plants. Plantations are frequently injured 

 from this cause. A good illustration is seen at Gosford, near 

 Edinburgh, where the trees, on reaching the top of a wall, are 

 stopped in then* growth by the sea breeze, and then* tops form an 

 inclined plane proceeding inwards from the wall as a base. Some 

 plants withstand this influence better than others.* The following 

 trees, shrubs, and herbs have been recommended as withstanding 

 the sea air : — 



Acer Pseudo-Flatanus. 

 Pinus Strobus. 



Pinea. 



Cembra. 



Pinaster. 



Quercus Ilex. 

 Pyrus Aria. 

 Hippophae rhamnoides. 



Hippophae conferta. 

 Tamarix galliea. 



germaniea. 



Pyrus japonica. 

 Leycesteria forrnosa. 

 Spiraea salicifolia. 

 Colutea eruenta. 

 Sambueus racemosa. 



The attacks of parasitic fungi cause extensive injury and disease 

 in trees. Some think that the spores of fungi coming into contact 

 with the plant act both as the predisposing and exciting cause of 

 disease ; others, perhaps more correctly, think that some change 

 is first produced in the cells, which enables the spores to find a 

 nidus, and then the disease goes on rapidly, assuming a peculiar 

 type on account of the presence of the fungus. 



Dry rot is a disease to which the wood of trees is liable. It 

 may be traced, in the first instance, to some alteration in the 

 woody tissue produced by moisture or other causes, and the sub- 

 sequent development of a fungus which spreads its myceliiim 

 through the texture, and produces rapid disorganisation. Trees 



* See two Papers by Mr William Gilchrist and Mr C. Y. Michie, in vol. v. 

 of the Transactions of the Society. 



