CHE REFERENCE LIBRARY - Pole Shift Survival Information

116 TIIE NURSERY-MA NiJAL
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. l2C3 (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 grrlf ted. 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 nffinities. 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. Sonietirnes plants of very distinct genera unite
rea.dily. Thus :~mong caclt i, the leafless zygocactus (usually
known as epiph~~lluni) 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, healthfuhless and loilgevity of the cion.
The bean has been known to make a union with the chrysanthemum,
but it almost immediately died. Soft, tissues, in
particular, often combine in plants that possess no affinity
whatever, as we commonly understand the term. Keither
does affinity refer to relative sizes or rat,es 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