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CHAPTEE IV. 



PROTECTION AGAINST DAMAGE FROM INORGANIC CAUSES. 



Non - parasitic Diseases or serious physiological disturbance 

 predisposing trees to disease can be caused by injurious in- 

 fluences in soil or atmosphere. 



The Soil may be unfavourable through being too shallow, 

 dry, or wet. A dry soil is naturally poor in the amount of 

 plant-food in an available soluble form, and consequently the 

 crops are usually backward, stunted, and likely to become 

 attacked by insects and fungus diseases. Stagheadedness or 

 partial or total death of the crown, often the first stage of decay 

 from old age, is frequently induced by want of water and nourish- 

 ment in the subsoil, though also common when Oaks and other 

 trees are heavily thinned after growing long in close canopy, 

 or when standards over coppice are pruned of lower branches ; 

 for shoots flush along the stem and intercept the sap on its 

 upward flow. Stagheadedness also often follows any sudden 

 lowering of the water-level in the soil, by drainage, railway- 

 cuttings, &c. ; and Willows and Poplars soon become stag- 

 headed on dry soil. Stagheaded broad-leaved trees often live 

 for many years, but Conifers soon die. Trenching round and 

 filling up with manure afford a temporary remedy for old 

 ornamental trees. A stiff soil and a wet soil that has not 

 been well drained before planting are both deficient in oxygen, 

 so that the roots get suffocated and rot away, especially in the 



