90 
M. Vermorel tersely defines it: ‘‘A ‘graft is a common 
cicatrix, or healing of two wounds placed in contact.” 
It is performed in a manner and under conditions such that 
they unite, and the scion will derive from his host, the stock, the 
nourishment necessary for its growth, and will bear fruit of the 
kind belonging to the plant from which it was taken. 
On some idea of the circumstances which make grafting 
practicable, and of the methods suitable to the performance of 
this operation depend the success or the failure of the graft. To 
be successful, grafting must be made with the right kind of wood. 
The stock and the scion must be botanically related; the closer 
the relationship the more successful the graft. Grafting is not 
practicable on all kinds of plants, but is restricted to thuse botani- 
cally known as exogenous plants, which are possessed of pith, 
wood, and bark, and grow outwardly. This term is used in contra- 
distinction to that of endogenous, which refers to a class of plants 
which inerease by internal growth and elongation at the summit 
instead of externally, and have no pith, wood, and bark. Reeds, 
palms, and cereals belong to this order, and, for the reason referred 
to, cannot be grafted. ; 
In order that grafting may be successful, the growing tissues 
of both stock and scion must be closely fitted together, so that the 
nourishing fluid may be forced by one into the other. For such 
an interchange to take place the growing tissues of each must be 
fresh, sound, and gorged with moving sap; the tissues conveying 
such sap must be in contact. This growing tissue is botanically 
known as cambium, a word which means “exchange.’”’ It consists 
of a layer of extremely delicate tissue formed between the wood 
and the bark. The cells of this tissue have very thin walls, and they 
are filled with protoplasma, or a gummy organisable nutrient matter. 
It shows like a thin film of mucilage. These cells develop on the 
one side into sap-wood or alburnum, which means “whitish,” and on 
the other side into new bark, whilst at the same time fresh cambium 
is formed for the continuation of the work. 
This fusion or union of these protoplasma cells or callus forma- 
tion is more active as the temperature becomes warmer, hence 
spring time is favoured for the operation. Biological laboratory 
observations in connection with the artificial callusing of ‘“bench- 
erafted” vines show very little callus formation at 68° F. at the end 
of eight days; at 77° F. it is plentiful, and still more so at 86° FP. 
This explains the greater percentage of suecess achieved when graft- 
ing is done when spring is well on. 
OBJECTS OF GRAFTING. 
This operation, which has been practised for ages without 
number, possesses advantages which are often availed of by the 
fruit-grower. 
