The flower is regular, ☿, and _hypogynous_. The gamopetalous type is
present in this family with great uniformity, without suppression
or splitting; S5, P5, A5, G2 (3–5). The stamens are all fertile,
alternating with the lobes of the corolla. Gynœceum with 2, more
seldom 3–5 syncarpous carpels. Style nearly always simple; 2 dorsal
stigmas. In each carpel 2–∞ ovules. At the base of the ovary is found
a yellowish ring-like nectary (Fig. 552 C), sometimes 5-sinuate or
5-partite.--The leaves are nearly always scattered; stipules are
absent.--~The Solanaceæ, which formerly were classed here, are so
closely allied to the Personatæ, that it would be unnatural not to
place them first in this family; and the Boraginaceæ (which were also
placed in the Tubifloræ) appear to be best united, with the Labiatæ and
others, into one family Nuculiferæ.~
Order 1. =Polemoniaceæ.= The flowers are regular; S5, P5,
A5, G3. The calyx and corolla have united leaves, the petals
_twisted_ to the right in _æstivation_ (all the left edges
being covered). The ovary is 3-locular with 2–∞ ovules in
each loculus; the style is trifid at the apex; the fruit
is a 3-valved capsule. Embryo straight; endosperm fleshy.
The inflorescences are dichasia passing over into unipared
helicoid cymes (the shoot of the _lower_ bracteole being the
more strongly developed).--Herbs without latex. 150 species;
especially Western N. Am.--_Phlox_ (salver-shaped corolla;
entire, opposite leaves), _Polemonium_ (campanulate or almost
rotate corolla; scattered, pinnate leaves), _Leptosiphon_,
_Gilia_, _Collomia_, _Cobæa_ (climbing, like the Vetches, by
tendrils at the ends of the leaves), etc. They are frequently
ornamental plants.
Order 2. =Hydrophyllaceæ.= This order approaches very closely to
the Boraginaceæ. Herbs with pinnate or palmate leaves; S5, P5,
A5, G2. The lobes of the corolla are imbricate in æstivation.
Generally 2 median carpels. The ovary is _most frequently
unilocular_, and the seeds are situated on 2 _parietal
placentæ_; capsule 2-valved; embryo straight; endosperm fleshy.
In the corolla-tube, opposite the corolla-lobes, there are
frequently appendages of various forms, which resemble those of
_Cuscuta_. The inflorescences correspond exactly with those of
the Boraginaceæ, being _unipared scorpioid cymes_, which, prior
to opening, _are tightly rolled up_.--130 species, especially in
N. Am. (California, etc.). Many annual species of _Phacelia_,
_Nemophila_, _Whitlavia_, _Eutoca_, _Cosmanthus_, etc., are
cultivated in gardens as ornamental plants. _Hydrolea_ (has a
bilocular ovary, and two free styles).
Order 3. =Convolvulaceæ= (=Bindweeds=). The flower is regular,
hypogynous, with 5 almost free sepals (quincuncial æstivation), P5,
A5, G2 (rarely 3–5). The _corolla_ is very characteristic; it is
(with various forms) almost entire, or slightly 5-lobed, and _folded_
longitudinally _in the bud_ in such a way that 5 projecting, flat
portions, tapering towards the top and frequently differing in colour
and hairiness from the rest, are visible externally and applied close
together, while the remainder of the corolla is folded inwards (Fig.
552 A); and hence the whole corolla is _strongly twisted to the right_
in the bud. The gynœceum most frequently has a bilocular ovary; _in
each loculus_ there are _only_ 2 (erect) _anatropous ovules_ on the
placenta, which is not especially thickened (Fig. 552 _D_, _E_); each
loculus is sometimes divided into two by a false septum (a relationship
with the _Boraginaceæ_, etc.); style simple with most frequently a
bilobed stigma, or a bipartite style. The fruit is nearly spherical,
most frequently a _capsule_. The seeds are erect, and have a large
hilum at the base. The embryo is _curved_, with leaf-like, thin,
bilobed, most frequently folded cotyledons; _endosperm absent or
mucilaginous_.
=1.= CONVOLVULEÆ, BINDWEED GROUP. The majority are _twining_ (to
the left) _herbs_, with _latex_. The leaves are scattered, without
stipules, often long stalked, and nearly always with cordate base;
some are palmately lobed. The flowers are most frequently solitary
in the leaf-axils, large, quickly withering.--_Convolvulus_ (Fig.
552), _Calystegia_ (unilocular ovary, 2 large bracteoles), _Ipomœa_,
_Batatas_, _Evolvulus_ (with a doubly bifid style), _Calonyction_,
_Pharbitis_, etc.
[Illustration: FIG. 552.--_Convolvulus scammonia._]
=2.= DICHONDREÆ. This group is a more primitive form, not twining,
and without latex. It has 2 _free_ carpels with basal style (as in
Boraginaceæ) and valvate corolla.
=3.= CUSCUTEÆ, DODDER GROUP (Fig. 553). Parasites, with round,
filamentous stems, bearing only scale-like leaves and almost destitute
of chlorophyll (they are reddish or yellowish); they are parasitic
upon other plants, around which they twine, first with narrow, compact
coils from which haustoria (Fig. 553 _A_) are developed which enter the
host-plant, and then with wider coils by which they raise themselves
to other portions of their host or try to reach other plants. On
germination a very temporary primary root is developed, which bears
root-hairs as far as the tip (rootcap is wanting); it only serves as a
kind of reservoir for water, and perishes very soon after the seedling
has fastened on to a host. The embryo is filamentous and rolled up
_spirally_ (Fig. 553 _C_), and is sometimes destitute of cotyledons.
The flowers are crowded into capitulate inflorescences, complicated
by accessory shoots (Fig. 553 _A_); they have S5, P5 (_imbricate_
æstivation), A5 (and beneath the stamens 5 scales on the corolla-tube),
G2. Fruit a capsule opening by a lid.--_Cuscuta europœa_, _C.
epilinum_ (Flax-Dodder), _C. epithymum_ (Lesser-Dodder), _C. trifolii_
(Clover-Dodder), etc., are parasitic on different hosts, or parasitic
each on its own particular host.
[Illustration: FIG. 553.--_Cuscuta trifolii_, parasitic on Red
Clover. _A_ A portion of the stem with an inflorescence and
haustoria (mag.); _B_ seed (nat. size); _C_ seed (mag.); _D_
embryo (nat. size).]
840 species; the majority in the Tropics, especially Am. Many
are ornamental plants. OFFICINAL: some on account of their
purgative properties: the tuberous roots of _Ipomæa purga_
(Jalap, from Mexico) and the dried latex (“Scammony”) of
_Convolvulus scammonia_ (from the East). The tuberous roots of
_Batatas edulis_ (Trop. S. Am.) are used as a common vegetable
(Sweet Potato) in the Tropics.