The type of the flower is: S5, P5, A5 (of which one, or in some cases
several, are suppressed), and G2. The flowers are _hypogynous_, ☿,
perfect with gamopetalous corolla, but most frequently irregular
(medianly zygomorphic, except _Solanaceæ_), the _corolla_ being
_bilabiate_ (divided into a posterior part of two lobes and an anterior
part of three lobes), and the _stamens_ 4, _didynamous_ (the posterior
being suppressed). The ovary has 2 loculi (only 1 in _Utriculariaceæ_,
_Gesneriaceæ_, _Orobanche_); the placenta in the first-named orders
(1–7) is most frequently very thick, and bears a _great many ovules_
(Figs. 554, 555, 557, 562); the number of ovules in the last orders
(8–9) is considerably reduced (Fig. 570).
Special mention may be made of the apparently 4-merous flower which
is found, _e.g._ in _Veronica_ and _Plantago_ (Figs. 567, 562 _C_,
570, 571), and which arises from the typical 5-merous flower by the
suppression of the posterior sepal and the posterior stamen, and by
the union of the two posterior petals into one.--Terminal flowers
very seldom occur on the main axis, and would not harmonise well
with the very irregular form of the flower. When they do occur, they
are, as a rule, “peloric,” _i.e._ regular (in _Linaria vulgaris_ two
kinds of peloric flowers occur,--one with 5 spurs, and one without
spurs). The halves of the anthers are often divided as far as the
base, and laterally so widely separated from each other as to assume
an almost straight line (Figs. 563, 564). There is generally a nectary
(“disc”) round the base of the ovary, often 5-lobed (or divided into
free glands).--A common vegetative characteristic is the _absence of
stipules_.
The 9 orders of the Personatæ are: 1, Solanaceæ; 2, Nolanaceæ;
3, Scrophulariaceæ; 4, Utriculariaceæ; 5, Gesneriaceæ; 6,
Bignoniaceæ; 7, Pedaliaceæ; 8, Acanthaceæ; 9, Plantaginaceæ.
[Illustration: FIG. 554.--Diagram of _Petunia_.]
Order 1. =Solanaceæ.= The flower (Figs. 554, 555, 559) is hypogynous,
regular (zygomorphic in _Hyoscyamus_), ☿, and gamopetalous, with
S5, P5 (most frequently _imbricate_ or _valvate_), A5, G2, the 2
carpels being placed obliquely (Fig. 554); the bilocular ovary has a
very _thick axile placenta_ (Figs. 554, 555 _H_, 557), which extends
almost as far as the wall of the ovary. The fruit is a capsule
or berry; the seeds are more or less reniform, and the embryo is
_curved_ (rarely straight), in a fleshy endosperm (Figs. 555 _F_, _G_;
561).--Both arborescent and herbaceous forms are found in the order;
leaves scattered without stipules, but with variously formed laminæ
(always penninerved). _A peculiar leaf-arrangement_ is found in many
species, viz. the leaves are borne _in pairs, a large and a smaller
one together_; these pairs stand in 2 rows, and the flowers are then
situated _between_ the individual leaves in each pair, apparently _not_
in a leaf axil. The inflorescences are frequently unipared scorpioid
cymes without floral-leaves.
[Illustration: FIG. 555.--_Atropa belladonna_: _A_ is reduced.]
Zygomorphic flowers occur, and thus form a transition to the
closely allied Scrophulariaceæ; the zygomorphy sometimes
shows itself only in the relative length of the stamens,
sometimes also in the corolla (_Hyoscyamus_).--_Nicandra_ is
5-merous throughout all the whorls.--The peculiar relative
_leaf-arrangement_ in this order occurs from sympodial branching
and displacement. The most simple is, _e.g._ _Datura_ (Fig. 556
_A_); each shoot-generation in the floral parts of the plant has
only 2 foliage-leaves (_f^1_ and _f^2_), and then terminates
in a flower; the axillary buds of both the foliage-leaves
are developed and form a dichasium, but since the leaves are
displaced on their axillary-shoots as far, or almost as far, as
the first leaf of these axillary-shoots, the flowers are borne
singly on the dichasial branches, and all the branches appear to
be without subtending leaves (Shoot I is white, II shaded, III
white, etc., diagram _A_). _Scopolia_ and others (Fig. 556 _B_)
differ in that the lowest and smallest (_f^1_) of the two leaves
on each shoot is barren, and is therefore not displaced; but the
upper one (the second bracteole, _f^2_) is displaced as in the
first instance, and consequently it assumes a position near the
first leaf (the shaded leaf _f^2_ of shoot I being placed near
the white leaf _f^1_ of shoot II, etc.,) of the next youngest
shoot-generation, and hence the leaves are borne in pairs; the
flower placed between the two leaves of a pair is therefore the
terminal flower of the shoot to which the smaller of the two
leaves belongs, and the larger leaf is the subtending leaf for
the floral shoot itself.
[Illustration: FIG. 556.--Diagrammatic representation of the
branching in Solanaceæ. The various shoot-generations are white
or shaded.]
[Illustration: FIG. 557.--Fruit of _Hyoscyamus niger_ after
removal of calyx.]
[Illustration: FIG. 558.--Fruit of _Datura stramonium_.]
=A.= FRUIT A CAPSULE. _Nicotiana_ (Tobacco) has a 2-valved capsule with
septifragal dehiscence; the valves separate at the apex; the corolla is
funnel-shaped, tubular, salver-shaped or campanulate. The flowers in
panicles.--_Datura_ (_D. stramonium_, Thorn-apple) has a (frequently
spiny) capsule (Fig. 558), which is _falsely 4-locular_ (at the top,
bilocular) and opens septifragally with 4 valves. The lower part of
the calyx persists as a thick collar (see Fig. 558). The corolla
is funnel-shaped. The flowers are solitary, large.--_Hyoscyamus_
(_H. niger_, Henbane) has a pyxidium (Fig. 557) enclosed in the
campanulate, completely persistent, thick-walled calyx. The flowers
are slightly _zygomorphic_, and borne in unipared scorpioid cymes.
~_Scopolia_ (pyxidium); _Fabiana_ (Heather-like shrub); _Petunia_
(slightly zygomorphic flower; funnel-shaped corolla); _Nierembergia_;
_Brunfelsia_ (almost a drupe); _Franciscea_; _Browallia_.~--Among
those with capsular fruits are found the most anomalous forms, which
by their zygomorphic flowers and often didynamous stamens present the
transition to the Scrophulariaceæ: _Salpiglossis_; _Schizanthus_ (lobed
petals; 2 perfect, and 3 rudimentary stamens).
[Illustration: FIGS. 559–561.--_Solanum tuberosum._
FIG. 559.--Flower (1/1).
FIG. 560.--Stamen, ejecting pollen.