the fact
that the number of trees in each group-unit is seven.
Equilateral triangle system refers to the planting of the trees
in equilateral triangles, but is identical with the hexagonal
or septuple.

[Illustration: FIG. 31. Hexagonal Planting System.]

It is the only system whereby each tree is placed equally
distant from each of its adjoining neighbors, and the only
system which equally divides the space among the trees. By this
method about fifteen per cent. more trees can be set per acre
than by the rectangular.

For permanent plantings, at regular distances, this system and
the rectangular should be recommended before other systems.

LAYING OUT BEFORE PLANTING.

Level and smooth the ground, harrow and pulverize thoroughly, then
proceed to stake the ground off, placing a stake for every tree.

_Laying Out Squares or Rectangles with the Plow._ If a good
plowman can be secured, very satisfactory work can be done with
the plow. In some cases a man can be found who needs nothing in
the way of a guide, except two or three stakes. But with a
sufficient number of stakes and a marker attached to the plow,
good results can be secured by almost any plowman.

Furrows should be run both lengthwise and crosswise of the
field, their intersections marking the place where the trees
are to stand. At each one set a stake.

It is essential that a true, square corner should be secured.
This may be done by sighting with an ordinary carpenter's
square set upon three posts.

_Laying Out in Rectangles with a Wire._ A wire, long enough to
reach down one side of the field, should be provided. Stretch
this straight out between two posts and mark off the distance
which the trees are to stand apart, upon it. At each point
marked, firmly twist a piece of small wire about the larger
one. These should then be soldered in place. It will not do to
have them shift. This wire may be rolled upon a roller when not
in use.

Measure off along both ends of the field and set small stakes
on the tree rows, at the marked places on the wire. Tightly
stretch the wire down the first tree row, attaching it firmly
at the ground level to a pair of good, stout posts. Then plant
a lath stake at each mark on the wire. Set all of them on the
outside of the wire, so as