GRAFTING AND NURSERIES. 



235 



when removing the surface roots, that the ligature is too 

 tightly bound, it should be cut with a knife. But sulphate 

 of copper is a very caustic compound, and 

 "burns" the tissues with which it is in 

 contact, even when in small quantity, and 

 checks the division and multiplication of 

 the cells in the stages of their develop- 

 ment; it is, therefore, a great obstacle to 

 the formation of the knitting tissue, and 

 consequently to the success of the graft. 

 Some nurseries have often had extensive 

 failures through the use of bands contain- 

 ing too much sulphite of copper. It 

 should, therefore, be used with caution, 

 and, in order to diminish its caustic effect, 

 the bands should be washed carefully with 

 water to remove the excess of sulphate of 

 copper; enough will remain fixed in the 

 tissues to preserve the bands from too 

 rapid decay. Or, better, the graft may be 

 separated from the sulphated raffia by a 

 thin sheet of lead or tin (Figs. 117 to 121) ; 

 then when removing the roots in July or 

 August the bands which have not rotted 

 should be cut. 



The lead foil does not facilitate the R^fly&w. 

 knitting nor does it appear to prevent 

 the growth of roots at the base of the scion ; but it is 

 rather an obstacle to the formation of callus, first, in 

 preventing the contact of air with the cells during the 

 process of division and multiplication ; second, and also 

 perhaps by penetrating the new tissues in the form of car- 

 bonate of lead, which is a poison. But its action in that 

 sense is practically nil, and need not be taken into account. 

 On hundreds of thousands of grafts made as above with 

 lead foil we have not noticed any check. In any case its 

 action is incomparably less than that resulting from the 

 direct contact of the sulphate of copper with the knitting 

 tissues. The foil prevents the entrance of water at the base 

 of the scion ; this is an advantage in wet soils, but rather a 

 nuisance in dry soils. Anyhow, its use is more and more 

 discarded, except in damp soils, where its employment is an 

 advantage. 



