236 THE FRUIT GROWER'S GUIDE. 



with gum. It prevails most in trees that are gross and sappy, but it also assails weakly 

 trees. The predisposing cause of gum appears to be defective food and assimilation, 

 inasmuch as we have seen little of it in really healthy trees. Thus, lifting and root- 

 pruning, with the addition of fresh soil, or an admixture of counteracting substances, 

 with firmer staple and shallower planting, cures the plethoric tree of its tendency to 

 gum ; whilst a weakly tree may be strengthened and fortified against attacks by im- 

 proving the soil, -clay marl being good for mixing with porous sandy soil, and then 

 with appropriate food supplies the tree is better able to resist the attacks of the enemy, 

 which is represented in the illustration Fig. 62. 



Peaches and nectarines, with other stone fruits grown against walls or under glass, 

 are most liable to receive injuries. These may be slight, yet sufficient to admit Cory- 

 neum spores, and everywhere precautions should be redoubled to prevent this con- 

 tagious disease. In nearly every instance of young trees much cut at the top and but 

 little at the roots, wounds and acute angles are formed by the branches which become 

 seats of acute gum disease. Any young tree showing gum in its stem and angles of 

 the radiating branches should be at once burned. Older trees that do not produce 

 clean healthy wood free from gum after a second or third careful lifting and rectifica- 

 tion of soil constituents and staple, should also be burned. But there are conditions of 

 culture essential to stone-fruit trees successfully resisting gum. Thus the apricot and 

 cherry gum in heavy wet soils and in deep alluvial deposits, whilst the plum is 

 nowhere so free from the malady as in calcareous clay. The cherry puts 19-98 per 

 cent, of silica, and 41-95 per cent, of lime in its bark ; while the plum strengthens its 

 external covering with a similar percentage of lime, and iron supplants silica to a large 

 extent. The plum also secures 28-06 per cent, of lime and 4-37 per cent, peroxide of 

 iron in the shell of its fruit, safeguarding its skin with 8 -25 per cent, of lime and 

 7-45 per cent, of peroxide of iron, when these essentials are provided. Other stone- 

 fruit trees similarly fortify themselves against their parasitic enemies. 



There is little doubt that heavy manuring induces the development of fungoid 

 diseases, and that top dressings of artificials are inimical to them. The exclusive use 

 of stable manure in gardens, under the erroneous impression that it contains everything 

 essential to tree growth and fructification, induces plethoric poverty in trees, rendering 

 them susceptible to gum disease. 



A suitable mixture for trees inclined to plethora and gum is : superphosphate of 

 lime, 5 pounds ; muriate of potash, 2 pounds ; sulphate of iron, 1 pound; mix, and apply 



