GENERAL PRACTICE, DISEASES. 



23? 



The greatest possible preventive of canker is care all round. Wounds must not be 

 inflicted needlessly. Accidents happen, but there is no occasion for subjecting fruit 

 trees to abuse in performing cultural operations, or for breaking branches. Pruning in 

 severe weather, or when there is danger of frost occurring to enlarge the wounds or 

 cause the bark to die back, is to be deprecated. All wounds should be made smooth and 

 protected by a fungus-proof coat. Shellac 

 solution and the cement advised for li in- 

 lay ed " buds (page 13G) answer for the 

 smaller, whilst the larger wounds should 

 be covered with the plastic substance named 

 at page 125 for covering grafts. 



Notwithstanding all precautions the Nec- 

 triu spores gain entrance to apple and pear 

 tree tissues, and in them set up canker. 

 Prompt measures must be instituted to 

 prevent the disease spreading. This is 

 comparatively easy because local. The 

 spawn threads of the fungus pass cell by 

 cell, and obtain nourishment from the proto- 

 plasm of the cells of the tree, impairing or 

 destroying its vitality. Certain manurial 

 elements, applied to the soil and entering 

 the affected trees, strengthen their cellulose, 

 whilst acting inimically upon the parasitic 



. nii i References : 1, apple branch with Nectria, show- 



growth. Sulphates possess this property. ing the cracks in bark occupied by the fungug . 2> 



The Sulphur is believed to act as food for circles at top, pink spore-capsules magnified 40 dia- 

 meters, showing apical orifices for escape of spores ; 



the protoplasm of vegetable cells, increasing 3> two bladders at left, asci with sporidia (spores) 



the growth 13-54 per Cent. Professor A. ma g nified 4 diameters; 4, spore magnified 1,000 



diameters. 



Miintz found iron sulphate increased the 



growth 30-2 per cent., and the chlorophyll 9'6 per cent. "It destroys parasitic fungoid 

 diseases " (Griffiths), and should be applied as a top-dressing early in spring, when the 

 soil is wet, at the rate of a quarter to half an ounce per square yard. To insure its 

 even distribution, mix it thoroughly with ten times its weight of finely-powdered dry 

 clay for light soil, and sand for heavy soil. The rain will wash it in. 

 VOL. i. H H 



Fig. 61. NECTBIA DITISSIMA FUNGUS CAUSING CANKEB. 



