ir secure fastening in the soil. The real mouths by which the food is
taken in are the minute tips of the hair-like roots found over the
surface of the smaller branches. As trees especially need a strong
support, they all have either a _tap-root_--one large root extending
from the lower end of the trunk deep down into the ground; or _multiple
roots_--a number of large roots mainly extending outward from the base
of the trunk.

Trees with large tap-roots are very hard to transplant, and cannot with
safety be transferred after they have attained any real size. The
Hickories and Oaks belong to this class.

Trees having multiple roots are readily transplanted, even when large.
The Maples and Elms are of this class.

Roots that grow from the root-end of the embryo of the seed are called
_primary roots_; those growing from slips or from stems anywhere are
_secondary roots_.

Some trees grow luxuriantly with only secondary roots; such trees can
readily be raised from stems placed in the ground. The Willows and
Poplars are good examples of this group. Other trees need all the
strength that primary roots can give them; these have to be raised from
seed. Peach-trees are specially good examples, but practically most
trees are best raised from seed.

A few trees can be easily raised from root-cuttings or from suckers
which grow up from roots. The Ailanthus, or "Tree of Heaven," is best
raised in this way. Of this tree there are three kinds, two of which
have disagreeable odors when in bloom, but the other is nearly odorless.
By using the roots or the suckers of the third kind, only those which
would be pleasant to have in a neighborhood would be obtained. One of
the large cities of the United States has in its streets thousands of
the most displeasing of these varieties and but few of the right sort,
all because the nurseryman who originally supplied the city used
root-cuttings from the disagreeable kind.

If such trees were raised from the seed, only about one third would be
desirable, and their character could be determined only when they had
reached such a size as to produce fruit, when it would be too late to
transplant them. Fruit-trees, when raised from the seed, have to be
grafted with the desired variety in order to secure good fruit when they
reach the bearing age.

CHAPTER II.

_Stems and Branches._

The stem is the distinguishing characteristic of trees, separating them
from all other groups of plants