of the latter, represent the
vine family (_Vitaceae_ or _Ampelidae_), and the buckthorn (_Rhamnus_)
is the type of the _Rhamnaceae_.

[Illustration: FIG. 109.--_Eucylae_ (_Frangulinae_), _Tricoccae_. _A_,
flowers of spindle-tree, _Euonymus_, (_Celastraceae_), x 1. _B_,
cross-section of the ovary, x 2. _C_, diagram of the flower. _D_, leaf
and fruit of bitter-sweet (_Celastrus_), x 1/2. _E_, fruit opening and
disclosing the seeds. _F_, section of a nearly ripe fruit, showing the
seeds surrounded by the scarlet integument (aril). _em._ the embryo,
x 1. _G_, flower of grape-vine, _Vitis_ (_Vitaceae_), x 2. The corolla
has fallen off. _H_, vertical section of the pistil, x 2. _I_, nearly
ripe fruits of the frost-grape, x 1. _J_, cross-section of young
fruit, x 2. _K_, a spurge, _Euphorbia_ (_Euphorbiaceae_), x 1/2. _L_,
single group of flowers, surrounded by the corolla-like involucre,
x 3. _M_, section of the same, [Male], male flowers; [Female], female
flowers. _N_, a single male flower, x 5. _O_, cross-section of ovary,
x 6. _P_, a seed, x 2. _Q_, longitudinal section of the seed, x 3.
_em._ embryo.]

The fifth group of the _Choripetalae_ is a small one, comprising but a
single order (_Tricoccae_). The flowers are small and inconspicuous,
though sometimes, as in some _Euphorbias_ and the showy _Poinsettia_
of the greenhouses, the leaves or bracts surrounding the inflorescence
are conspicuously colored, giving the whole the appearance of a large,
showy, single flower. In northern countries the plants are mostly
small weeds, of which the various spurges or _Euphorbias_ are the most
familiar. These plants (Fig. 109, _K_) have the small flowers
surrounded by a cup-shaped involucre (_L_, _M_) so that the whole
inflorescence looks like a single flower. In the spurges, as in the
other members of the order, the flowers are very simple, being often
reduced to a single stamen or pistil (Fig. 109, _M_, _N_). The plants
generally abound in a milky juice which is often poisonous. This juice
in a number of tropical genera is the source of India-rubber. Some
genera like the castor-bean (_Ricinus_) and _Croton_ are cultivated
for their large, showy leaves.

The water starworts (_Callitriche_), not uncommon in stagnant water,
represent the family _Callitrichaceae_, and the box (_Buxus_) is the
type of the _Buxaceae_.

[Illustration: FIG. 110.--Types of _Calyciflorae_ (_Umbelliflorae_).
_A_, inflorescence of wild parsnip, _Pastinaca