46 PLANT PROPAGATION 
celebrated ancient writers accounts are given of various 
attempts having been made, and supposed unions 
effected, under conditions which have since been found 
impossible, on account of a natural affinity being non- 
existent. A temporary union has sometimes taken place, 
but not a vital and lasting one. 
A fundamental principle, which applies to every 
method of grafting, is the necessity for forming a direct 
communication between the layers of inner bark in each 
of the parts to be united, as without this a perfect join- 
ing is not effected. The pithy or woody parts never 
unite, as may be frequently observed when grafting 
trees of long standing are cut down and the ends of 
wood originally placed in contact are found to have 
become decayed. Provided this essential principle be 
kept in view, the methods of grafting may be varied 
almost indefinitely. 
The natural vigour of the stock and scion should be 
somewhat similar for inducing a steady growth, but at 
times it is preferable that the scion should be the 
hardier and more vigorous of the two. This is exem- 
‘plified, and the desired results are obtained in many 
cases, by grafting various strong-growing varieties of 
Apples on the Paradise stock, Cherries on the Mahaleb, 
and Pears on the Quince. In these and other instances 
the stock is restricted in its root growth, and the supply 
of sap transmitted to the grafted portion is consequently 
limited. This latter condition tends to encourage fruit- 
bearing instead of vigorous wood, and proves, by 
results, the modifying effect of the stock and the 
superior results in productiveness thereby secured. 
Double-grafting is sometimes adopted as another 
means for reaching the same end by having a variety of 
