Oaks, the
whole forms an _acorn_. [Illustration] If the coating has spiny hairs,
as in the Chestnut and Beechnut, the whole is a _bur_. The coating in
these cases is an _involucre_. If the coating or any part of the fruit
has a regular place for splitting open, it is _dehiscent_ (Chestnut,
Hickory-nut); if not, _indehiscent_ (Black Walnut).

[Illustration: Fig. 12.]

Dry fruits with spreading, wing-like appendages, as in the Ash (Fig.
11), Maple (Fig. 12), Elm (Fig. 13), and Ailanthus, are called _samaras_
or _keys_.

Dry fruits, usually elongated, containing generally several seeds, are
called _pods_. If there is but one cell and the seeds are fastened along
one side, _Pea-like pods_, or _legumes_. Locust. The term _capsule_
indicates that there is more than one cell. Catalpa, Hibiscus.

[Illustration: Fig. 13.]

All the dry, scaly fruits, usually formed by the ripening of some sort
of catkin of flowers, will be included under the term _cone_. Pine,
Alder, [Illustration] Magnolia. If the appearance of the fruit is not
much different from that of the cluster of flowers, as in the Hornbeams,
Willows, and Birches, the term _catkin_ will be retained for the fruit
also. The scales of a cone may lap over each other; they are then said
to be _imbricated_ or _overlapping_, [Illustration] (Pine); or they may
merely touch at their edges, when they are _valvate_ [Illustration]
(Cypress). When cones or catkins hang downward, they are _pendent_. If
the scales have projecting points, these points are _spines_ if strong,
and _prickles_ if weak. The parts back of the scales are _bracts_; these
often project beyond the scales, when they are said to be _exserted_.
[Illustration] Sometimes the exserted bracts are bent backward; they are
then said to be _recurved_ or _reflexed_.

CHAPTER V.

_Winter Study of Trees._

Many of the peculiarities of trees can be studied much better during the
winter and early spring than at any other time of the year. The plan of
branching, the position, number, size, form, color, and surface of buds,
as well as the arrangement of the leaves within the bud and the
peculiarities of the scales that cover them, are points for winter
investigation.

GENERAL PLAN OF BRANCHING.--There are two distinct and readily
recognized systems of branching. 1. The main stem is _excurrent_ (Fig.
3) when the trunk extends as an undivided stem throughout the tree to
the tip; this causes the spire-like or co