116 THE NURSERY-MANUAL 



ing of uncongenial kinds are surely to be avoided, but it is now 

 too late to raise the question in the abstract. 



Grafting is not unknown in nature. Often limbs of trees 

 grow together solidly when they cross. Fig. 129 (left) shows a 

 natural graft of two trunks which in some way became en- 

 tangled. Fig. 129 (right>) is a similar case, but here the four 

 trunks were tied together intentionally and are now grown 

 into a firm union. In these cases the trees are of the same 

 kind or species. 



The limit within which graftage is possible or desirable 

 between species, is determined only by experience. Probably 

 all exogenous plants those with a distinct bark and pith 

 can be regularly grafted. Plants must be more or less closely 

 related to allow of successful graftage of the one on the other. 

 As a rule, plants of close botanical relationship, especially those 

 of the same genus, intergraft with more or less ease; yet this 

 relationship is by no means a safe guide, particularly as the 

 current fashion among taxonomists of splitting up genera into 

 fragments obscures affinities. A plant will often thrive better 

 on a species reputed to be of another genus than on a congener. 

 The pear, for example, does better on many thorns than on 

 the apple. Sometimes plants of very distinct genera unite 

 readily. Thus among cacti, the leafless zygocactus (usually 

 known as epiphyllum) grows well on the leaf-bearing pereskia. 

 It should be borne in mind that union of tissues is 

 not a proof of affinity. Real affinity can be measured only 

 by the thrift, healthfulness and longevity of the cion. 

 The bean has been known to make a union with the chrysan- 

 themum, but it almost immediately died. Soft tissues, in 

 particular, often combine in plants that possess no affinity 

 whatever, as we commonly understand the term. Neither 

 does affinity refer to relative sizes or rates of growth of stock 

 and cion, although the term is sometimes used in this sense. 

 It cannot be said that some varieties of pear lack affinity for 



