POLLINATION. _Fumaria_, with its inconspicuous flowers, has to
a great extent to resort to self-pollination. _Corydalis_, on
the other hand, is dependent on cross-pollination; _C. cava_
is even absolutely sterile with its own pollen. _Corydalis_
is pollinated by insects with long probosces (humble-bees,
bees), which are able to reach the honey secreted in the spur;
as they alight on the flowers they press the exterior petals
on one side (Fig. 396 _e_), so that the stigma, surrounded by
the anthers, projects forward; the proboscis is introduced in
the direction of the arrow in the figure, and during this act
the under-surface of the insect is covered with pollen, which
is transferred by similar movements to the stigma of another
(older) flower.--Ornamental plants; _Dicentra_ (_spectabilis_
and _eximia_), _Adlumia_, _Corydalis_.
Order 3. =Cruciferæ (Crucifers).= The flowers are _regular_, ☿; sepals
4, free (2 + 2), deciduous; petals 4, free, deciduous, unguiculate,
placed _diagonally_ in one whorl, and alternating with the sepals;
stamens 6; the 2 _outer_ are _short_, the 4 _inner_ (in reality the two
median split to the base) _longer_, placed in pairs (tetradynamia of
Linnæus); gynœceum syncarpous formed by 2 (as in the previous order,
lateral) carpels, with 2 parietal placentæ, but divided into two
loculi by a _spurious_ membranous dissepiment (_replum_) (Fig. 397).
Style single, with a capitate, usually two-lobed stigma, generally
commisural, that is, placed above the parietal placentæ (Fig. 397), but
it may also be placed above the dorsal suture, or remain undivided.
Ovules _curved_. The fruit is generally a bivalvular _siliqua_ (Fig.
398 _B_, _C_), the valves separating from below upwards, and leaving
the placentæ attached to the replum; other forms of fruits are
described below. The oily seeds _have no endosperm_ (endosperm is
present in the two previous orders); the _embryo is curved_ (Figs.
398 _E_, _F_; 399, 400).--In general they are _herbaceous_ plants,
without latex, with scattered, penninerved leaves, without stipules;
the inflorescence is very characteristic, namely, a raceme with the
flowers aggregated together at the time of flowering into a corymb, and
_destitute of both bracts and bracteoles_.
[Illustration: FIG. 397.--Diagram of a Cruciferous flower.]
[Illustration: FIG. 398.--_Brassica oleracea_: _A_ raceme; _B_,
_C_ siliqua; _D_ seed; _E_ embryo; _F_ transverse section of
seed.]
[Illustration: FIG. 399.--Transverse section of seed and embryo
of _Cheiranthus cheiri_.]
[Illustration: FIG. 400.--Transverse section of seed of
_Sisymbrium alliaria_.]
Many are biennial, forming in the first year a close
leaf-rosette. By cultivation the tap-root can readily be induced
to swell out into the form of a tuber (Turnips, Swedes, etc.).
_Stipules_ are found indicated by small glands on the very
young leaves; in _Cochlearia armoracia_ they are fairly large
triangular scales. _Stellate hairs_ often occur. _Floral-leaves_
are occasionally developed. Terminal flowers are never found in
the inflorescences. _Iberis_ and _Teesdalia_ have _zygomorphic_
flowers. _Subularia_ (Fig. 403) is perigynous. The 2 external
sepals (Fig. 397) stand in the median plane; it may therefore
be supposed that there are two bracteoles outside these which,
however, are suppressed, and can only in a few instances be
traced in the young flower; the two lateral sepals are often
gibbous at the base, and serve as reservoirs for the nectar
secreted by the glands placed above them; they correspond in
position to the external petals of the Fumariaceæ. The 4 petals
which follow next arise simultaneously, and alternate with the
4 sepals; if it could be shown that these are merely 2 median
petals, which have been deeply cleft and the two parts separated
from each other and displaced to the diagonal position, there
would be a perfect correspondence with the Fumariaceous flower;
then the petals would be followed in regular alternation by the
2 lateral small stamens, the 2 median long stamens, which it
has been proved are split into 4 and placed in couples, and the
2 laterally-placed carpels,--in all 6 dimerous whorls. But the
formation of the corolla by the splitting of 2 petals does not
agree with the development of the flower or bear comparison, and
hence the only fact in favour of this theory is the otherwise
prevailing correspondence with the Fumariaceæ. Yet it may
be observed that in special cases each pair of long stamens
clearly enough arises from one protuberance and even later
on may be considerably united or entirely undivided (_e.g._
_Vella_); in other instances they are quite distinct from the
beginning, and it is possible that this latter condition has
become constant in the corolla. _Lepidium ruderale_ and others
have no corolla. _Senebiera didyma_ has only 2 median stamens.
_Megacarpæa_ has several stamens, no doubt by dédoublement, as
in Capparidaceæ.--The _number of carpels_ may also be abnormally
increased; _Tetrapoma barbareifolium_ has normally 4 carpels
with an equal number of placentæ and repla. It is supposed to
be a variety of _Nasturtium palustre_.--The 2–4–8–10 greenish
_glands_, which are found at the base of the stamens, are
nectaries, morphologically emergences, and not rudimentary
stamens. The forms of _fruits_ are of great systematic
significance, see the genera. In some species dimorphic fruits
are present, _e.g. Cardamine chenopodiifolia_ which has both
ordinary _Cardamine_-siliquas and 1-seeded siliculas.
The _curved embryo_ appears in five forms, which have
systematic importance: 1. To the PLEURORHIZÆ belong those
genera whose radicle (with the hypocotyl) lies bent upwards
along the _edge_ of the _flat_ cotyledons (Fig. 399); to
this group belong _Cardamine_, _Nasturtium_, _Cheiranthus_,
_Matthiola_, _Cochlearia_, _Draba_, _Iberis_, _Thlaspi_, etc.;
diagrammatic transverse section: ◯=.--2. To NOTORHIZÆ belong
those whose radicle lies in an upward direction along the
_back_ of one of the _flat_ cotyledons (Figs. 400, 413); _e.g._
_Hesperis_, _Sisymbrium_, _Lepidium_, _Capsella_, _Camelina_:
◯‖.--3. ORTHOPLOCEÆ differ from the Notorhizeæ in having the
cotyledons folded (not flat) (Fig. 398 _E_, _F_); to this belong
_Brassica_, _Sinapis_, _Raphanus_, _Crambe_, etc.: ◯>>.--4.
SPIROLOBEÆ: the radicle lies as in the Notorhizæ, but the
cotyledons are so rolled together that a transverse section of
the seed cuts them twice; _Bunias_: ◯‖‖.--5. DIPLECOLOBEÆ: the
cotyledons are folded forward and backward so that a transverse
section cuts them several times; _Subularia_, _Senebiera_: ◯‖‖‖.
On _germination_ the cotyledons appear above the ground as green
leaves; in the Orthoploceæ they are bilobed, in the _Lepidium_-species
divided.
1. =Silicula, broad replum= (Siliculosæ latiseptæ), valves flat or
slightly vaulted, and the replum extends through the greatest width of
the silicula (Fig. 404). The seeds are situated in two rows.
◯=: _Cochlearia_ (Horse-radish): the siliqua is nearly spheroid;
glabrous herbs, generally with fleshy, stalked leaves, and white
flowers.--_Draba_ has an oblong, lanceolate, somewhat compressed
silicula; herbs with small rosettes of leaves, most frequently with
stellate and long-stalked racemes.--_Alyssum_ and _Berteroa_ are
whitish, on account of the stellate hairs; they have a more compressed
and round or elliptical silicula. _Vesicaria_; _Aubrietia_. _Lunaria_
(Honesty, Fig. 401): very broad and flat silicula with long stalk (the
receptacle as in Capparidaceæ).
◯‖: _Camelina_ (Gold-of-pleasure) has a spheroid, pear-shaped siliqua
with a small rim passing right round (Fig. 402). _Subularia_ (Awlwort),
an aquatic plant with _perigynous_ flower (Fig. 403) and folded
cotyledons.
2. =Silicula, narrow replum= (Siliculosæ angustiseptæ), _i.e._ the
replum is much shorter than the arched, more or less boat-shaped valves
(Figs. 405, 406, 407).
[Illustration: FIG. 401.--_Lunaria biennis._ Fruit, the valves of
which have fallen off.]
[Illustration: FIG. 402.--_Camelina sativa._ Fruit.]
[Illustration: FIG. 403.--_Subularia aquatica._ Longitudinal
section through the flower.]
◯=: _Thlaspi_ (Penny-Cress) has a flat, almost circular silicula,
emarginate or cordate, with a well-developed wing round the edge (Fig.
406). _Iberis_ and _Teesdalia_: the racemes during flowering are
especially corymbose, and the most external petals of the outer flowers
project radially and are much larger than the other two (the flower is
_zygomorphic_).--_Biscutella_, _Megacarpæa_.
◯‖: _Capsella_ (Shepherd’s-Purse) has a wingless, obcordate or
triangular silicula (Fig. 407). _Lepidium_ (Pepperwort) has a few–(2–4)
seeded, slightly winged, oval silicula. _Senebiera_ has a silicula
splitting longitudinally into two nut-like portions; its cotyledons are
folded.--~_Anastatica hierochuntica_ (“Rose of Jericho”) is an annual,
silicula-fruited, desert plant (Arabia, Syria, N. Africa). After the
flowering all its then leafless branches bend together upwards, forming
a kind of ball; this spreads out again on coming in contact with water,
and the fruits then disseminate their seeds, which germinate very
quickly, often in the fruit.~
3. =Siliqua= (Siliquosæ). The fruit is a true siliqua, several times
longer than broad. The seeds in most are borne apparently in one row.
[Illustration: FIG. 404.--Transverse section of a silicula with
broad replum: _s_ replum; _k_ the valves.]
[Illustration: FIG. 405.--Transverse section of a silicula with
narrow replum.]
◯>>: _Brassica_ (Cabbage). The seeds are placed apparently in one
row in each loculus (Fig. 398 _C_); the style is long and round; the
valves have only 1 strong, longitudinal rib.--_Melanosinapis_ (_M.
nigra_, Black-mustard); the style is compressed, two-edged; the valves
of the siliqua are one ribbed.--_Sinapis_ (Mustard); quadrangular or
flat style (in which in most cases there is a seed) and 3–5 strong,
longitudinal ribs on the valves.--_Eruca_ differs from _Brassica_ by
the shorter siliqua, broad, sword-like “beak” and seeds in two rows.
◯= (Fig. 399): _Cardamine_ (Bitter Cress) has a long, linear siliqua,
with flat, unribbed, _elastic_ valves. The leaves are most frequently
pinnatifid or pinnate. ~_C. pratensis_ reproduces by buds formed
in the axils of the leaves.~--_Arabis_ (Rock Cress); _Matthiola_
(Stock); _Cheiranthus cheiri_ (Wallflower); _Barbarea_ (Winter Cress)
(double-edged, quadrangular siliqua); _Nasturtium_ (_N. officinale_,
Water-cress); the siliqua of the latter genus is in some species short,
in others long.
[Illustration: FIG. 406.--_Thlaspi arvense._]
[Illustration: FIG. 407.--Silicula of _Capsella bursa-pastoris_.]
◯‖ (Fig.400): _Sisymbrium_ (Hedge Mustard) the valves of the siliqua
are 3-ribbed.--_Erysimum_; _Hesperis_; _Schizopetalum_ (with fimbriate
petals).
4. =Fruit jointed= (Lomentaceæ). The fruit is divided by transverse
walls into as many spaces as there are seeds, and dehisces at maturity,
generally _transversely_, into a corresponding number of nut-like
joints (“articulate-siliqua.”)
◯=: _Crambe_ (Kale, Fig. 408). The fruit has only 2 joints. The lower
one resembles a short, thick stalk, and is barren, the upper one is
spherical, and has 1 seed.--_Cakile_ (_C. maritima_, Sea-kale); the
lower node is triangular, 1-locular, the upper one more ensiform,
1-locular (Fig. 409).
[Illustration: FIG. 408.--Fruit of _Crambe maritima_.]
[Illustration: FIG. 409.--_Cakile maritima._ Fruit (2/1).]
[Illustration: FIG. 410.--_Raphanus raphanistrum._]
[Illustration: FIG. 411.--_Raphanus sativus._]
◯>>: _Raphanus_ has a long siliqua, which, in the garden Radish (_R.
sativus_), is spongy and slightly abstricted (Fig. 411), but neither
opens nor divides transversely (a kind of dry berry), and which in the
Wild Radish (_R. raphanistrum_) (Fig. 410) is abstricted in the form
of a string of pearls, and separates into many joints. ~_R. sativus_;
the “Radish” is formed by the hypocotyl, after the bursting of its
external, cortical portions (of which there are generally two patches
at the top of the Radish).~
5. =Siliqua indehiscent= (Nucumentaceæ). The fruit is a short,
_unjointed_, unilocular and 1-seeded nut, and the fruit-stalks are
often long, slender, and drooping. (Sometimes a thin endosperm is
present).--_Isatis_ (Woad) has most frequently an oblong, small-winged
nut; ◯‖ (Figs. 412, 413).--_Bunias_; _Neslia_.
[The systematic division of this order given above is founded
upon that of A. P. de Candolle. Prantl (_Engler and Prantl, Nat.
Fam._), 1891, adopts a somewhat different system, which may
briefly be summarised as follows:--
_A._ Hairs unbranched or absent; no glandular hairs.
1. THELYPODIEÆ. Stigma equally developed on all sides; style
undivided or prolonged above the middle of the carpels,
or turned back.--_Stanleyinæ_; _Heliophilinæ_.
2. SINAPEÆ. Stigma strongly developed above the placenta;
style beaked or two-lobed.
_a._ Cotyledons arising behind the bend of the
embryo.--_Lepidiinæ._
_b._ Cotyledons arising at the bend of the embryo.
α. Only lateral nectaries. Generally a silicula or
indehiscent fruit.--_Cochleariinæ._
β. Generally a siliqua, more rarely a silicula or
transversely-divided or indehiscent fruit.
Nectaries generally lateral and
median.--_Alliariinæ_; _Sisymbriinæ_; _Vellinæ_;
_Brassicinæ_; _Cardamininæ_.
_B._ Hairs collectively or partially branched, very rarely
entirely absent; glandular hairs are sometimes also present.