The very large order _Euphorbiaceæ_ and three smaller ones belong to
this family. They have in common: _unisexual_, hypogynous, frequently
regular flowers, the perianth most frequently single, rarely double, or
entirely wanting; there is such a great variety in the structure and
parts of the flower that one only can be cited as the _rule_: viz. the
simple gynœceum composed of 3 carpels forming a 3-locular ovary, which
is frequently more or less deeply grooved (hence the name, _Tricoccæ_);
in the inner angles of the loculi are found 1 or 2 (never several)
pendulous (except _Empetraceæ_), anatropous ovules, with upward and
outwardly turned, frequently swollen, micropyle (Fig. 455). The seed
most frequently has a large endosperm and a straight embryo (Figs.
455 _B_, 464).--~The family approaches the nearest to the Gruinales
and Columniferæ; it may perhaps be regarded as an offshoot from the
Sterculiaceæ.~
Order 1. =Euphorbiaceæ.= Flowers unisexual. In each of the loculi of
the ovary, generally 3, there are 1 or 2 pendulous ovules with upward
and outwardly turned micropyle. The placenta protrudes above the ovules
(Figs. 454, 461 _B_). On the ripening of the capsule the 3 carpels
separate septicidally, frequently with great violence, ejecting the
seeds and leaving a central column. Endosperm copious.--For the rest,
the flowers present all stages, from genera with calyx and corolla,
to those which are the most reduced in Nature, namely the naked,
1-stamened flowers of _Euphorbia_.
The same variety which is found in the flower is also present in the
vegetative parts. Some are herbs, as our Spurges, others are shrubs
and trees; some African _Euphorbia_-species even resemble the habit
of a Cactus. Leaf-like branches with rudimentary leaves are found in
_Phyllanthus_ (sub-genus _Xylophylla_) (Fig. 456). The leaves are
scattered or opposite, often stipulate; they are nearly always simple.
Large, highly-branched cells containing a great quantity of pungent
latex are found in many, and watery juice in others. Glands and
glandular hairs are general.--Only a few genera can be considered in
this book.
As an example of the most perfect flowers (which partly reproduce
the Geraniaceous type) may be mentioned, _Croton_, _Manihot_, and
_Jatropha_; 5 sepals, 5 petals, sometimes gamopetalous, andrœcium
diplostemonous, or many-stamened, often monodelphous.
[Illustration: FIGS. 453–455.--_Ricinus communis._
FIG. 453.--♂-flower (magnified).
FIG. 454.--♀-flower in longitudinal section.