ROSACEOUS FRUITS ] 187 



square metre, and then digging deeply and soaking 

 thoroughly with water. Sulphate of magnesia (Epsom 

 salt) is also known to be an efficient corrective for 

 infected soils, and is distributed either in substance 

 or as a fairly strong solution. 



The stone fruits are further linked together by their 

 common liability to exude gum from breaks and wounds in 

 the bark of the stem, branches and twigs. This is of course a 

 diseased condition and may be due to various pathogenic 

 causes. Wounds in the bark caused by pruning in 

 summer or by accidental injuries may cause an exudation 

 of gum in the shape of drops or of irregular worm- 

 like lumps which are usually transparent and colourless 

 or may be tinged yellow or red. A plethora of sap 

 in the course of the summer provoked by a sudden 

 excess of moisture in the soil, brought about by 

 irrigation, is sure to cause breaks in the bark attended by 

 an abundant flow of gum. Independently of these physical 

 causes, an abundant formation of gum in summer or 

 autumn, either as small drops disseminated all over 

 the stem and branches, or as large lumps of dirty, 

 dark, semiliquid gum, is a sure indication of root trouble, 

 particularly if at the' same time the tree is in a sickly 

 condition with weak growth and chlorotic foliage, and 

 the tree will probably succumb in the course of the 

 following winter. The unhealthy state of the roots 

 may be due to various causes, such ns an excess 

 of humidity with bad drainage, a long and exhausting 

 period of drought followed too suddenly by liberal 

 irrigation, the presence of fermenting organic material, 

 or an excess of nitrogenous manures, but here again 

 the most frequent cause of trouble is the insidious 

 presence of the mycelium of root-rot fungi above 

 referred to. 



