The leaves are most frequently _opposite_, _simple_, _entire_ (rarely
dentate), and _exstipulate_. The flowers are _regular_ and _epigynous_
(perigynous in _Lythraceæ_ and a few others), ☿, polypetalous; the
number of members in a whorl is generally 4 or 5 (S, P, A, or most
frequently A 2, G), but sometimes it becomes (_e.g._ Myrtles and
_Lythraceæ_) very large in the andrœcium by splitting, and in the
gynœceum also is often different. (When suppression takes place it is
principally in the corolla and petal-stamens.) In nearly all instances
the calyx is _valvate_. Gyncœceum multicarpellary, multilocular,
with only one _style_ (except _Haloragidaceæ_). In the majority the
ovules are situated on an axile placenta in the multilocular ovary.
_Endosperm is wanting_ in the majority.--~Less important exceptions:
_Rhizophoraceæ_ and _Gunnera_ have stipules. _Haloragidaceæ_ have
several styles and endosperm. _Rhizophora_ also has endosperm.~
Order 1. =Lythraceæ.= _Hermaphrodite_, _perigynous_ flowers which are
_most frequently =6=-merous_, viz. S 6 (often with a _commissural_
“_epicalyx_,” Fig. 519 _c_), one segment posterior, P 6, A 6 + 6 or
6 + 0 and G =2–6=, forming a 2–6-locular ovary with many ovules in
the loculi, style single, and capitate stigma. The _gynœceum is free_
at the base of the tubular, or bell-shaped, _thin_, strongly veined
receptacle, which bears the other leaf-whorls on its edge and inner
side. Fruit a capsule. No endosperm.--To this order belong both herbs,
shrubs and trees. The branches are frequently square, the leaves always
_undivided_, _entire_, and without stipules, or with several very
small stipules, and often opposite. The calyx is valvate. The flower
is regular (except _Cuphea_) and frequently large and beautiful. The
stamens are generally incurved in the bud, and the petals irregularly
folded.
[Illustration: FIG. 519.--_Lythrum salicaria._ _c_ the
“epicalyx.”]
_Lythrum_ (Loose-strife). The flower is diplostemonous and 6-merous,
with a long, tubular receptacle with epicalyx-teeth (Fig. 519 _c_).
The 12 stamens are arranged in two tiers on the inner side of the
receptacle. The gynœceum is bicarpellary. ~The flowers are borne
in small dichasia in the leaf-axils, and their number is increased
by accessory inflorescences beneath the main inflorescence.--The
native species, _L. salicaria_, is trimorphic (long-styled, mid-and
short-styled forms, Fig. 520). Cross-pollination is chiefly
effected by humble-bees and bees, which seek the nectar formed at
the bottom of the receptacle. Other species are only dimorphic,
or even monomorphic.~--Closely allied are, _Nesæa_, _Diplusodon_,
_Lagerstrœmia_, and _Cuphea_, whose flower resembles that of _Lythrum_,
but is zygomorphic. In _Cuphea_ the receptacle is oblique and at the
back prolonged into a _spur_, in which the nectar, secreted by a
gland situated behind the ovary, is collected; the calyx and corolla
gradually become reduced in size toward the anterior side of the
flower; the reverse, however, is the case with the 11 stamens (the
posterior one is absent); the posterior loculus in the bilocular ovary
is sometimes barren; the fruit, when ripe, dehisces along the posterior
side, the ovary as well as the wall of the receptacle being ruptured
by the placenta, which expands and projects freely. ~The flowers stand
singly in the centre of the stem, between the pairs of leaves. This
may be explained as follows: of the two foliage-leaves in each pair,
one supports a foliage-shoot, the other a flower; the foliage-shoot
remains in the axil, but the flower is displaced through the length
of an entire internode to the next pair of leaves, and then assumes
a position between these two leaves. All foliage-shoots stand in two
rows, the flowers in two other rows.~
[Illustration: FIG. 520.--_Lythrum salicaria._ One side of the
perianth is removed from all three flowers. _A_ is long-styled,
_B_ mid-styled, and _C_ short-styled. The direction of the arrows
and dotted lines indicates the best (legitimate) methods of
crossing.]
_Peplis_ (Water-purslane), a small, annual plant, with thin,
bell-shaped receptacle without projecting nerves. The small
flowers have no petal-stamens, and often also no corolla; fruit
indehiscent.--_Ammannia_ is closely allied to it.
365 species; 30 genera; mostly in the Tropics, and more
especially S. Am.--Some yield _dyes_, _e.g._ _Lawsonia inermis_
(cultivated in Africa and Asia) and _Lagerstrœmeria indica_;
some contain tannin; others are ornamental plants, especially in
gardens in warm countries.
Order 2. =Blattiaceæ.= 12 species. Tropical Asia and Africa.
Trees. Formerly included with _Punica_, but best placed as an
independent order.
Order 3. =Melastomaceæ.= A very natural and very large order
(150 genera; 2,500 species), its home being chiefly in tropical
S. America, especially the Brazils (termed by Schouw “The
kingdom of Palms and Melastomaceæ”). There are both herbaceous
and arborescent species, which are easily recognized by the
opposite or verticillate, simple leaves which have (with the
exception of a few heather-like species) 3–5–7–9 curved veins
proceeding from the base of the leaf, and connected very
regularly by closely parallel, transverse veins. The flower
is perigynous or epigynous; its type is that of the Onagraceæ
(4–5-merous; 1 whorl of sepals, petals and carpels, 2 of
stamens); the calyx is valvate, the corolla is twisted (to
the left) in æstivation; the stamens are very characteristic;
in the bud they are geniculate; the anther opens in the often
long, beak-like, prolonged point, with 1, less frequently with
2 pores, and has generally ear-like appendages at its base.
The fruit is a berry or capsule. These large and beautiful
flowering-plants play a very important part in South American
landscapes; otherwise they are of slight importance (a few are
cultivated in conservatories, _e.g._ _Centradenia_, _Medinilla_,
_Lasiandra_, _Tibouchina_, _Miconia_, etc.).
Order 4. =Œnotheraceæ= (or =Onagraceæ=). The flowers are arranged in
racemes or spikes, ☿, epigynous, regular, polypetalous, _=4=-merous in
all 5 whorls_ (1 whorl of sepals, petals and carpels, 2 of stamens);
2–3–5–6-merous flowers are less frequent; _the calyx is valvate_, the
_corolla twisted_ in æstivation (the left edge being covered). Gynœceum
simple with multilocular ovary; the _style is undivided_, filiform,
and bears a capitate or 4-partite stigma; endosperm wanting; embryo
straight.--The majority are herbs, especially water- and marsh-plants;
several are shrubs. No essential oils. The leaves are alternate or
opposite, always single, and without (or with very small) stipules.
~The odourless flowers sometimes have a coloured calyx. In some
instances (_e.g._ _Œnothera_, _Fuchsia_) the receptacle is prolonged
more or less beyond the inferior ovary, and finally falls off. The
stamens are obdiplostemonous (carpels epipetalous); the petal-stamens
are sometimes suppressed. The anthers in some genera are divided into
storeys. The well-pronounced, triangular pollen-grains are connected
together by viscous threads. Small stipules are sometimes found, _e.g._
_Fuchsia_, _Lopezia_.~
[Illustration: FIG. 521.--Flower of _Lopezia_.]
=A.= =Fruit a capsule.= _Œnothera_ (Evening Primrose) is 4-merous,
has 8 stamens, a tubular receptacle, and an oblong capsule with
loculicidal dehiscence leaving a centrally placed column, bearing
the seeds.--_Epilobium_ (Willow-herb) deviates from _Œnothera_
especially in the seeds being hairy (at the chalazal end of the
seed).--_Chamænerium_ is a Willow-herb with zygomorphic flowers.--~The
following may be included here: _Clarkia_, _Eucharidium_ (an _Œnothera_
with 4 stamens and 3-lobed petals), _Godetia_ and _Boisduvalia_,
_Jussiæa_ (dehiscence septicidal), _Isnardia_ (petal-stamens absent,
sometimes the petals also).--_Lopezia_ has a peculiar, zygomorphic
flower (Fig. 521); one of the four sepals is bent forwards and the
other 3 backwards; the posterior petals are narrower than the 2
anterior ones which are turned obliquely backwards and bent like
a knee, with a greenish nectary at the bend; 2 stamens, one only
fertile (the posterior), while the anterior is barren, petaloid, and
spoon-shaped; both are sensitive, which is essential for pollination.
In Fig. 521, _a_ represents an early stage, in which the stamen and
style lie concealed in the staminode; _b_ is the ♂ stage, the stamen
projects from the centre of the flower; _c_, the ♀ stage, the style
occupies the place of the stamen.~
=B.= =Fruit a berry.= _Fuchsia_ generally has a coloured calyx and
tubular receptacle; the corolla may be wanting.
=C.= =Fruit a nut.= _Circæa_ (Enchanter’s Nightshade) has a 2-merous
flower (S2, P2, A2 + 0 [petal-stamens are wanting], G2). The flowers
are borne in racemes without bracts.--_Gaura._
=D.= =Fruit a drupe.= _Trapa_ (Horn-nut); a peculiar aquatic plant;
the submerged stem has long internodes and lanceolate leaves, falling
off at an early period, but at each node are found 4 long roots with
thin, lateral roots (sometimes erroneously regarded as leaves) borne
pinnately; the stem reaching the surface of the water, bears a rosette
of rhombic foliage-leaves, with large, inflated stalks containing air,
and forming the floating apparatus of the plants. In the axils of the
leaves (as in _Gunnera_) 8 small, stipular structures are present. The
flowers are solitary in the axils of the foliage-leaves (S4, P4, A4 +
0, G2), _semi_-epigynous. There is an 8-lobed, crenate disc on the free
portion of the ovary; one ovule in each loculus. The fruit is a _drupe_
with 4 (or 2) prominent horns (the persistent sepals), which after the
pulp has decayed away bear a series of hooks turned downwards on each
side, _i.e._ sclerenchymatous bundles which formerly lay concealed
in the pulp of the sepals. ~The germination is peculiar: one of the
cotyledons is large, and its thick extremity remains in the fruit,
the other however is small and is pushed out at the apex of the fruit
together with the radicle and plumule; the development of the root soon
ceases, and the plumule usually grows into a stem entirely without
branches, similar to the one described above, only that 1–2 precisely
similar shoots arise in the axil of each cotyledon, so that each embryo
produces 3–5 shoots.--_Trapa_, by its mode of life, its 1-seeded fruit,
etc., forms a transition to _Haloragidaceæ_.~
The large-flowered forms are adapted for insect-pollination and
are often protandrous, the small-flowered ones are homogamous
and may pollinate themselves. _Œnothera_ is adapted for
hawk-moths and bees.--330 species; especially in temperate
climates, chiefly in the Northern Hemisphere. _Epilobium_,
_Circæa_ are natives of this country; _Trapa_ is extinct in this
country, it has been found in a semi-fossilized condition near
Cromer and in bogs in Denmark, and existed in Sweden until a few
years ago; _Œnothera_ has been introduced from N. Am.--A number
of N. Am. species are grown as ornamental plants in our gardens.
The seeds of _Trapa natans_ are edible, and used as food in
China.
Order 5. =Haloragidaceæ.= This is a reduced form of the Œnotheraceæ,
and principally differs from these in the presence of _endosperm_
and _free styles_. _Only 1 ovule in each loculus._--84 species
distributed over the entire globe; the majority are aquatic
plants. The most advanced type is _Myriophyllum_ (Water-Milfoil),
with a regular, epigynous flower (S4, P4, A4 + 4, G4), most
frequently _diclinous_ (monœcious); the fruit is a _2–4-partite
schizocarp_. Aquatic plants, most frequently with pectinate, pinnate
leaves.--_Haloragis._--~_Gunnera_ (a dozen species from the Southern
Hemisphere) forms the next step in the reduction. Large, scattered,
rough-haired, and softly-spined leaves, with small flowers in crowded
inflorescences. The flower, when most complete, has S2, P2, A2
(petal-stamens) and G2, forming an inferior, unilocular ovary with
1 ovule. It is remarkable for the great number of stipules placed
in transverse rows in the leaf-axils, for the peculiar glandular
organs, and for the colonies of _Nostoc_, which are found embedded in
the cortex as a kind of parasite.~--The simplest form is _Hippuris_
(Mare’s-tail) with an extremely small, crenate or entire calyx, without
corolla, and with only one stamen and one carpel, forming an inferior,
unilocular ovary with only one ovule. Fruit a drupe with thin pulp.
~It is an aquatic plant with creeping, sympodial rhizome, and erect
unbranched shoots, bearing numerous small, verticillate leaves. The
small flowers are situated singly in the leaf-axils.~
Order 6. =Rhizophoraceæ.= Tropical trees or shrubs (50 species,
the best known being _Rhizophora mangle_, Mangrove) which grow
gregariously, especially along the banks of rivers and by
sea-coasts, where the water is quiet and brackish, and where
they form the so-called Mangrove-swamps. Aerial roots are formed
on the stems and branches (Fig. 522 _A_). The seeds germinate
in the fruit, which by arrest contains only one seed (Fig. 522
_B_), before it is detached from the tree. The radicle projects
considerably from the seed, and hangs down freely in the air;
when the embryo is finally detached from the mother-plant,
the separation is effected by the hood-like cotyledon, which
entirely envelops the plumule, becoming detached from the rest
of the embryo, which falls down, while the hood-like cotyledon
remains enclosed in the fruit. The embryo, after it has fallen,
strikes root, and continues growing in the undisturbed mud
under the trees, or perhaps it may first be drifted about by
the water, being well adapted for this by its peculiar, tough
nature, and large, intercellular spaces.--It may also further
be remarked that the anther is divided into a number of small
loculi. The leaves are stipulate. The endosperm projects from
the micropyle, growing out from the base of the seed, and thus
serves as an organ of suction to convey nutriment to the embryo
from the mother-plant.
Order 7. =Combretaceæ.= Trees and shrubs, partly lianes.
An inferior, unilocular ovary with few pendulous ovules.
_Conocarpus_ and _Laguncularia_ form, in conjunction with
the species of Rhizophoraceæ, the tropical Mangrove-swamps.
_Terminalia._--280 species; Tropics.
[Illustration: FIG. 522.--_Rhizophora mangle_ with the germinating
fruit (much reduced).]
Order 8. =Myrtaceæ (Myrtles).= The plants belonging to this order are
shrubs or trees, the majority being easily recognised by the vegetative
characters. The leaves, for instance, are most frequently opposite,
without stipules, undivided and entire, parchment-like or leathery,
evergreen, _aromatic_, finely dotted by _pellucid glands containing
essential oils_; the venation is penninerved with a nerve just inside
and running parallel to the edge of the leaf. The flowers are regular,
epigynous (Figs. 523, 524, 525) and ☿, most frequently =4-= or 5-merous
in the calyx and corolla, with _many_ stamens (by splitting, so that
they are often in several distinct bundles) and an ovary with one
style, formed of 2–5–many carpels; the receptacle is most frequently
united for its entire length with the ovary. The fruit varies, but is
_most frequently a berry_. The embryo is thick, often curved, with
united cotyledons; no endosperm.
=1.= MYRTEÆ, MYRTLE GROUP. Chiefly American, though some are found also
in Africa and Asia. The fruit is a _berry_ with generally 2–5 loculi in
the ovary, and many ovules in each.--_Myrtus_; _Eugenia_ (the petals
fall off together as a hood in the Clove, _E. caryophyllata_, Figs.
523, 524); _Myrcia_; _Jambosa_; _Amomis_; _Psidium_, etc.
=2.= PUNICEÆ, POMEGRANATE GROUP. Only 2 species (_Punica granatum_;
from Persia, Afghanistan), differing in several respects from the
typical form of the Myrtaceæ. The leaves are generally _opposite_,
without glands and marginal veins. The receptacle, calyx and corolla
are red; the latter 5–8–(generally 6-) merous. Calyx valvate and
corolla folded as in Lythraceæ, stamens also and epicalyx as in this
order. The most characteristic feature is the inferior, spherical
berry, with dry pericarp, formed from two whorls of carpels in two
tiers (Fig. 525); the interior whorl, which is also the lower, has
3 carpels, and the placentæ are situated in the inner angles of the
3 loculi; the external whorl is 5-merous, and the placentæ have
originally the same position in the inner angles of the loculi, but
their position is changed to the outer side of the loculi owing to the
growth of the wall of the ovary, which takes place early, causing the
carpels to become, as it were, turned inside out, so that the part
which was turned downwards is turned upwards, and the part which was
turned inwards becomes turned outwards (as in _Mesembrianthemum_). The
edible part of the fruit is the _fleshy testa_, as in _Ribes_. The
cotyledons are rolled together spirally.
[Illustration: FIGS. 523, 524.--_Eugenia caryophyllata._
FIG. 523.--Flowers (nat. size).