MISSOURI BOTANICAL GARDEN BULLETIN 41 
Curious traditions were associated by the ancients with 
grafting operations. Thus Pliny emphasizes the fact that 
the graft must not be sharpened while the wind blows; and 
again, “It is a point most religiously observed to insert the 
graft during the moon’s increase.” 
There are numerous modes of grafting, but the one of 
present interest is that known as grafting by approach or 
inarching. If we believe, with Pliny, that this art was taught 
to man by nature, it is highly probable that examples of nat- 
ural inarching were the inspiration of present grafting prac- 
tices. Inarching differs from other modes of grafting in that 
it involves the union of two individuals growing on their own 
roots. When this method is used in horticulture, the plant 
intended for the scion is severed from its lower portion as 
soon as the union of the two individuals is complete. Natural 
grafts are, of course, purely the result of chance. The essen- 
tial condition for their development is the same as in artificial 
grafting, namely, that the region of actively growing cells— 
the cambium layer—of both plants shall be in close contact. 
In nature this is effected when two trees of the same or related 
species grow sufficiently close together for a branch of one 
to interlock with, or to grow across and in contact with, a 
branch of the other. The continued growth of both branches 
causes great pressure and friction, which is increased by 
winds, so that ultimately the bark is worn away, the cambium 
regions come in contact, and union of the limbs occurs. 
Plate 9, fig. 1, shows such a union of two red oaks (Quercus 
rubra) growing in Worcester, Massachusetts. 
Of more common occurrence than natural grafts between 
two individuals are those between two portions of the same 
plant. Trees furnish many examples of this type of union, 
which may be regarded as natural bridge grafting or self- 
grafting. Thus a tree, branching from its trunk, may de- 
velop limbs which unite in the manner just described. 
There are several examples of self-grafted trees in the Gar- 
den, which visitors may be interested in seeing. Plate 9, fig. 
2, shows a self-grafted hawthorn (Crataegus) on the left side 
of the path which parallels the east wall of the Garden, about 
two hundred feet north of the main entrance. If, upon en- 
tering the main gate, one turns directly to the left and takes 
the path to the south along the same wall, he will come to a 
striking self-grafted specimen of Osage orange, Maclura pomi- 
fera (Plate 10, fig. 1), one of a group of five trees about one 
hundred feet north of the Cleveland Avenue gate and about 
fifteen or twenty feet west of the path. In both hawthorn and 
Osage orange the union has been effected in several places, 
indicated by the arrows. 
