The primitive form resembles that of the preceding family. In it
we find the typical, perfectly developed, Monocotyledonous flower,
sometimes even with free carpels and with a dry or somewhat fleshy, but
never petaloid perianth; and this passes over into very different forms
by the suppression of the floral-leaves, perianth and sporophylls
(unisexual flowers are common), and by the close aggregation of the
flowers in the inflorescence. The flower is _hypogynous_ in every case.
The inflorescence is a _spike_ which may be either single or branched,
and has often a thick and fleshy axis (a _spadix_). In Palms and Araceæ
it is enveloped, at any rate prior to the opening of the flowers, by a
very large floral-leaf, _the spathe_, which may be petaloid (Figs. 297,
301).
The fruit is most frequently fleshy (_berry_, _drupe_) or a _nut_,
never a capsule. The embryo is small, with large, fleshy endosperm
(Fig. 299 _C_); very rarely the endosperm is wanting.
[Illustration: FIG. 295.--Piassava (_Attalea funifera_).]
[Illustration: FIG. 296.--A portion of the stem of _Attalea
funifera_ with persistent leaf-bases.]
The numerous plants belonging to this family are large, herbaceous or
tree-like, and the leaves seldom have the usual Monocotyledonous form,
_i.e._ linear with parallel venation, but most frequently have pinnate
or palmate venation.
Order 1. =Palmæ (Palms).= The majority are trees with an _unbranched_,
cylindrical _stem_, having short internodes and covered with leaf-scars
or the bases of the leaf-stalks (Fig. 296), and at the summit a rosette
of large leaves closely packed together (Fig. 295). An exception to
this is found in _Calamus_ (Cane, “Rotang”), whose thin, creeping or
climbing stems have long internodes; sparsely[28] branched is, _e.g._
the African Doum-palm (_Hyphæne_). Notwithstanding their often enormous
stems the Palms have fibrous roots, like the bulbous Monocotyledons.
The leaves are pinnate (Feather-palms, Fig. 298) or palmate (Fan-palms,
Fig. 295) and often very large; they have a well-developed petiole
with an _amplexicaul sheath_, which is often more or less separated
into a large number of fibres. _In the bud the blade is entire but
folded_, as the leaf expands the lines of folding are torn, either
those which are turned upwards (thus ∨ ∨ ∨ ∨, _e.g. Pritchardia_,
_Livistona_, _Phœnix_, _Chamærops_) or those turned downwards (thus
∧ ∧ ∧ ∧, _e.g. Cocos_, _Chamædorea_, _Calamus_). The inflorescence
is usually lateral; when, as in Sago-palm (_Metroxylon rumphii_)
or Talipot (_Corypha umbraculifera_) it is terminal, the plant is
monocarpic, and dies after flowering; it is often a very _large_
and _branched spadix_ with numerous flowers either borne externally
or embedded in it, and enclosed either in one woody, boat-shaped
_spathe_ (Fig. 297) or several spathes, in the latter case one for each
branch. The flowers are sessile or even embedded, regular, generally
_unisexual_ (monœcious or diœcious) with the usual diagram (Fig.
278); the perianth is inconspicuous, green or yellow, persistent, and
more or less leathery or fleshy. 6, rarely 3 or many stamens. The 3
carpels remain either _distinct_ or form one, generally 3-locular,
ovary. The style is short. There is _one ovule in each carpel_. Often
during ripening 2 carpels with their ovules are aborted. The fruit is
a _berry_, _drupe_ or _nut_, generally one-seeded, with a large horny
or bony endosperm with hard thick-walled cells (_e.g._ Date-palm). In
some (_e.g._ Cocoanut) it is thin-walled, soft, and oily; in several
“ruminate.”
When _germination_ commences in the Cocoanut, Date, etc., the
apex of the cotyledon remains in the seed and developes into
a spongy mass to withdraw the endosperm; in the Cocoanut it
attains a considerable size (Fig. 299 _C_) and assumes the
form of the fruit. The endosperm in the Cocoanut is hollow and
the interior is filled with “milk.” In the Date-palm and the
Vegetable-ivory (_Phytelephas_) the cell-walls of the hard
endosperm serve as reserve material.
=1.= PHŒNICEÆ. _Phœnix_ (Date-palm) has pinnate leaves with channeled
leaflets and diœcious flowers with 8 free carpels, of which usually
only one developes into a berry with membranous endocarp; the large
seed has a deep furrow on the inner side, and horny endosperm.
[Illustration: FIG. 297.--Inflorescence of a Palm with spathe. At
the top ♂-, at the base ♀-flowers.]
[Illustration: FIG. 298.--_Livistona australis._]
=2.= SABALEÆ. These have fan-like leaves with channeled segments;
flowers ☿ or polygamous, rarely diœcious, with 3 separate or only
slightly united carpels, all of which are sometimes developed
into fruits (berry or drupe, with thin stone).--_Chamærops_, the
Dwarf-palm. The pericarp is externally fleshy, internally more
fibrous, and provided with a membranous inner layer. The endosperm is
ruminate (that is, the testa is several times deeply folded into the
endosperm).--_Sabal_, _Copernicia_, _Livistona_ (Fig. 298), _Thrinax_,
_Corypha_, _Brahea_, and others.
[Illustration: FIG. 299.--_A_ Longitudinal section of a Cocoanut
(diminished), the inner layer only (the stone) not being divided
_B_ End view of the stone, showing the sutures for the 3 carpels
(_a_), and the 3 germ-pores; the embryo emerges from the lowest
one when germination begins. _C_ Germinating; inside the stone is
seen the hollow endosperm and the enlarging cotyledon.]
=3.= COCOINEÆ. With pinnate leaves. Monœcious inflorescence. The
carpels are united into a 3-locular ovary. The fruit is most frequently
1-locular, only 1 of the loculi becoming developed, rarely 3-locular;
it is a drupe with a large, fibrous, external layer (_mesocarp_) and
most frequently a very hard inner layer (_endocarp_, stone) which
has 3 germ-pores, the 2 of these, however, which correspond to the
suppressed loculi are closed; internal to the third lies the small
embryo (Fig. 299). Endosperm containing abundance of oil. _Cocos_ (the
Cocoanut-palm), _Attalea_, _Elæis_, _Acrocomia_, _Bactris_.
=4.= LEPIDOCARYINÆ. The floral-leaves and flowers are borne in 2
rows on the spadix. The carpels are united into one 3-locular ovary;
the fruit is coated by a layer of hard, shining, imbricate scales.
The majority of the species are thorny, and climb by means of the
thorny leaves. Some have fan-like (_Mauritia_), others pinnate leaves
(_Raphia_, _Calamus_, _Eugeissonia_, _Metroxylon_; the stems of the
latter die after the first flowering).
=5.= BORASSINÆ. Large Fan-palms without thorns, with 3-locular
ovary. Drupe with separate stones. _Latania_ and _Lodoicea_ have
many stamens; _Hyphæne_; _Borassus_ (Palmyra-palm).
=6.= ARECINEÆ. The most numerous group. Feather-palms. Berry.
_Areca_, _Euterpe_, _Oreodoxa_, _Ceroxylon_, _Chamædorea_,
_Geonoma_, _Caryota_ with bipinnate leaves.
=7.= PHYTELEPHANTINÆ. Flowers with rudimentary perianth united
in close capitula. _Phytelephas_ (Vegetable-ivory). _Nipa._
DISTRIBUTION. About 1,100 species are known. In Europe
only the Dwarf-palm (_Chamærops humilis_) is wild (Western
Mediterranean). The Date palm (_Phœnix dactylifera_) belongs
to North Africa and West Asia. Other African genera are
_Hyphæne_ (Doum-palm) and _Elæis_ (_E. guineensis_, Oil-palm).
A large majority of the genera are found in South America and
in the East Indies. The following are AMERICAN:--_Mauritia_,
_Acrocomia_, _Bactris_, _Chamædorea_, _Oreodoxa_, _Euterpe_,
_Attalea_, etc. ASIATIC:--_Metroxylon_, _Calamus_, _Areca_,
_Borassus_, _Lodoicea_ (“Double-cocoanuts,” Seychelles) and
others. The Cocoanut-palm has perhaps an American origin; all
the other species of the same genus being endemic in America;
it is the only Palm found on the coral islands of the Pacific
Ocean, and is also the only one which is common to both
hemispheres.
USES. Palms belong to the most useful plants; they contain no
poison, and are of little medicinal interest, but are largely
employed in the arts and manufactures, the hard timber being
adapted for many purposes on account of the hard tissue in
which the vascular bundles are embedded. “Cane” is the stem
of _Calamus_-species (from India). SAGO is obtained from the
pith of _Metroxylon rumphii_ (Sago-palm, Sunda-Is., Moluccas),
_Mauritia flexuosa_, etc. Sugar-containing sap (“palm wine”) is
obtained from the American _Mauritia vinifera_ and _flexuosa_,
_Borassus flabelliformis_ (Asiatic Palmyra-palm), _Arenga
saccharifera_, etc., by cutting off the young inflorescences,
or by perforating the stem before the flowering (_arrack_ is
distilled from this). _Vascular strands_ for the manufacture of
mats and brushes, etc., are obtained from the outer covering
(mesocarp) of the Cocoanut, and from the detached leaf-sheaths
of _Attalea funifera_ (Brazil) (Fig. 296). WAX is yielded by the
leaves of _Copernicia cerifera_ (carnaueba-wax, Amazon region),
and by the stem of _Ceroxylon andicola_ (palm-wax, Andes);
East Indian _Dragon’s blood_ is from the fruit of _Calamus
draco_; the young buds of many species, especially _Euterpe_,
_Cocos_, _Attalea_, etc., are used as “cabbage.” Palm-oil is
obtained from the oily mesocarp of the plum-like fruits of
_Elæis guineensis_ (W. Africa), and from the seeds, when it is
largely used in the manufacture of soap. EDIBLE FRUITS from the
Date-palm (_Phœnix dactylifera_, Arabia, Egypt, W. Africa), and
the endosperm of the Cocoanut (_Cocos nucifera_). The seeds
and the unripe fruits of the Areca-palm (_Areca catechu_)
are chewed with the leaves of the Betelpeper, principally in
Asia. VEGETABLE IVORY from the hard endosperm of _Phytelephas
macrocarpa_ (S. America.)--Many species are cultivated in
the tropics as ornamental plants, but in this country only
_Chamærops humilis_, _Livistona australis_ and _chinensis_ are
generally grown. In addition to the few just mentioned, many
others are of importance, but these are much the most useful.
Order 2. =Cyclanthaceæ.= This is a small order related to the
Palms (44 species from Tropical America), with fan-like, folded
leaves. The flowers are unisexual and arranged in whorls or
close spirals on an unbranched spadix. Ovary unilocular, ovules
numerous. To this belongs _Carludovica palmata_, whose leaves
are used for Panama hats.
Order 3. =Pandanaceæ= (Screw-pines) is another small order,
forming a transition to the Araceæ. The woody, (apparently)
dichotomous stem is supported by a large number of aerial roots,
which sometimes entirely support it when the lower portion of
the stem has decayed. The leaves are closely crowded together,
and arranged on the branches in three rows, which are often
obliquely displaced, with the formation of three spiral lines;
they are, as in the Bromeliaceæ, amplexicaul, long, linear,
the edge and lower midrib often provided with thorns. The
♂-flowers are borne in branched, the ♀ in unbranched spadices
or capitula, which resemble those of _Sparganium_, but have no
floral-leaves. Perianth absent. The drupes or berries unite into
multiple fruits.--About 80 species in the islands of the Indian
Ocean.--_Pandanus_, _Freycinetia_.--Fossils perhaps in the chalk
of the Harz.
Order 4. =Typhaceæ.= The flowers are unisexual, monœcious, and borne
on a cylindrical spike or globose capitulum; ♂ inflorescences above,
the ♀ below. The perianth consists of a definite number of scales
(_Sparganium_), or in its place numerous irregularly-arranged hairs are
found (_Typha_); in the ♂-flower there are generally three stamens; the
gynœceum is formed of 1–2 carpels with 1 prolonged style; 1 pendulous
ovule. The seeds are furnished with a seed-cover, which is cast off on
germination.--The few species (about 20) which belong to this order are
marsh plants with creeping rhizome (and hence grow in clusters); the
leaves on the aerial shoots are borne in two rows, entire, very long
and linear.
_Sparganium_ (Bur-reed). The flowers are borne in globose capitula;
the perianth distinct, generally consisting of 3 small scales; pistil
bicarpellate. Drupe, dry and woody. ~The stalk of the lower ♀ capitula
is sometimes united with the main axis, and consequently the capitula
are situated high above their subtending-leaf.~
_Typha_ (Bulrush, Reed-mace) has a long, cylindrical, brown spike,
the lower portion bearing ♀-flowers, and the upper ♂-flowers, which
is divided into joints by alternate leaves. The ♀-flowers have 1
carpel. The perianth is wanting, represented by a number of fine,
irregularly-placed hairs; pistil unicarpellate. Fruit a nut.
The two genera, according to some, are related to the 2nd order.
In both genera native species are found. The pollination is
effected by the wind, and consequently the anthers project
considerably, and the stigma is large and hairy. _Typha_ is
protandrous, _Sparganium_ protogynous. The small, fine hairs
surrounding the nut of _Typha_ assist in its distribution by the
wind.--Fossil _Typhas_ in the Tertiary.
Order 5. =Araceæ= (=Arums=). The flowers are small, and always borne
_without bracts or bracteoles_ on _an unbranched_, often very fleshy
spike, which is enclosed by a spathe, often petaloid and coloured (Fig.
301). The fruit is a _berry_. Outer integument of the seed fleshy.--The
leaves have generally sheath, stalk, and blade with distinctly
_reticulate_ venation; they are chiefly cordate or sagittate (Fig.
302), seldom long with parallel venation as in the other Monocotyledons
(_Acorus_, Fig. 300). The Araceæ are quite _glabrous_, generally
_perennial herbs_ with tubers or rhizomes. Many have latex.--For the
rest the structure of these plants varies; for example, while some
have a perianth, in others it is wanting; in some the perianth-leaves
are free, in others united; some have hermaphrodite flowers, but the
majority unisexual (monœcious); some have free, others united stamens;
the ovules are orthotropous, anatropous, or campylotropous, erect or
pendulous; the ovary is 1–many-locular; some have seeds with endosperm,
others without. ~_In habit_ there are great differences. While some,
_e.g. Colocasia_ (Fig. 302), have a thick, more or less upright stem,
with leaf-scars, but not woody, others are climbers, epiphytic, and
maintain themselves firmly by means of adventitious roots, on the stems
and branches of trees, or even on steep rocks, _e.g. Philodendron_;
the cordate, penninerved leaf is the most common (Fig. 302), but
various branched forms appear; the pedate leaves of _Helicophyllum_,
_Dracunculus_, etc., are cymosely branched; the leaves of _Monstera
deliciosa_, perforated by tearing, should be noticed (the vascular
bundles while in the bud grow faster than the tissue between them,
causing the latter to be torn, and the leaf perforated). With regard to
the anatomical structure, the presence or absence of latex, raphides,
resin-passages, groups of mucilage-cells should be noted. Engler makes
use of these anatomical peculiarities for a scientific arrangement of
the order.~
=A.= ORONTIEÆ, CALAMUS-GROUP. ☿, hypogynous flowers of a completely
formed monocotyledonous type (number in the whorls 2, 3, or
4).--_Acorus_ (_A. calamus_, Sweet-flag) has a regular, 3-merous,
pentacyclic flower (Fig. 300 _C_, _D_). They are marsh-plants, with
creeping rhizome, triangular stem, and long, sword-like leaves (Fig.
300 _A_); the inflorescence is terminal, apparently lateral, being
pushed to one side by the upright, sword-like spathe (Fig. 300
_B_).--~_Anthurium_ (Pr2+2, A2+2, G2); _Pothos_; _Orontium_ (unilocular
ovary with one ovule), etc.~
[Illustration: FIG. 300.--_Acorus calamus_: _A_ habit (much
reduced); _B_ inflorescence; _C_ a flower; _D_ diagram; _E_
longitudinal section of an ovary; _F_ an ovule.]
[Illustration: FIG. 301.--_Arum maculatum._ The spathe (_h_) in
_B_ is longitudinally divided.]
[Illustration: FIG. 302.--_Colocasia Boryi._]
=B.= CALLEÆ. Flowers hypogynous, naked, ☿.--_Calla_ (_C. palustris_).
All flowers in the spike are fertile, or the upper ones are ♂; 6–9
stamens; ovary unilocular with many basal ovules. Marsh-plants with
creeping rhizome and cordate leaves.--_Monstera_, _Rhaphidophora_, etc.
=C.= ARINEÆ. Flowers monœcious, naked, ♂-flowers on the upper, ♀ on the
lower part of the spadix.--_Arum_ (Fig. 301). The spadix terminates in
a naked, club-like portion (_k_); below this is a number of sessile
bodies (rudimentary flowers), with broad bases and prolonged, pointed
tips (_b_); underneath these are the ♂-flowers (_m_), each consisting
only of 3–4 short stamens, which eject vermiform pollen-masses through
the terminal pores; then follow, last of all, ♀-flowers (_f_), each of
which consists of one unilocular ovary, with several ovules. Perennial
herbs, tuberous, with cordate leaves.--~_Dracunculus_; _Biarum_;
_Arisarum_; _Pinellia (Atherurus) ternata_ with leaves bearing 1–2
buds. _Zantedeschia æthiopica_ (_Richardia_, Nile-lily); ♂, 2–3
stamens; ♀ with 3 staminodes, 1–5-locular ovary (S. Africa.)--In some
genera sterile flowers are present between the ♂ and ♀ portions of
the spadix (_e.g._ in _Philodendron_); in _Ambrosinia_ a lateral,
wing-like broadening of the axis of the spadix divides the cavity
of the spathe into two chambers, the anterior containing one ♀, and
the posterior 8–10 ♂-flowers in two series; in some the stamens in
the single ♂-flowers unite and form a columnar “synandrium” (_e.g._
in _Dieffenbachia_, _Colocasia_, _Alocasia_, _Caladium_, _Taccarum_,
_Syngonium_). A remarkable spadix is found in _Spathicarpa_; it is
united for its entire length, on one side, with the spathe, and the
flowers are arranged upon it in rows, the ♀ to the outside, and the
♂ in the middle (_Zostera_ has a similar one).--_Pistia_ similarly
deviates considerably, it is a floating water-plant, with hairy, round
rosettes of leaves; in it also the spathe and spadix are united; at the
base a ♀-flower is borne, which consists of one unilocular ovary, and
above several ♂-flowers, each composed of two united stamens.~
BIOLOGY. The inflorescences are adapted for
_insect-pollination_; they are protogynous, since the viscous,
almost sessile stigmas come to maturity and wither before the
pollen, which is generally dehisced by apical pores, is shed;
some pollinate themselves freely by the pollen from the higher
♂-flowers falling upon the ♀-flowers below them, and in some
it is conjectured that the pollination is effected by snails.
The coloured spathe, and the naked end of the spadix (often
coloured) of certain genera function as the coloured perianth in
other orders; during flowering a very powerful smell is often
emitted. _Arum maculatum_ is worthy of notice; small flies
and midges creep down into the spathe, between the sterile
flowers (Fig. 301 _b_), which are situated where the spathe is
constricted, and pointing obliquely downwards prevent the escape
of the insects; in the meantime, the stigmas are in a condition
to receive any pollen they may have brought with them; after
pollination the stigmas wither, and exude small drops of honey
as a compensation to the flies for their imprisonment; after
this the anthers (_m_) open and shed their pollen, the sterile
flowers wither, and the insects are then able to escape, and
enter and pollinate other inflorescences.--In many, a _rise
of temperature_ and evolution of carbonic acid takes place
during flowering; a spadix may be raised as much as 30°C. above
the temperature of the surrounding air.--Again, under certain
conditions, many species absorb such large quantities of water
by their roots that water is forced out in drops from the tip of
the leaf; this may often be observed in _Zantedeschia_.
About 900 species in 100 genera. Home, the Tropics, especially
S. America, India, and the Indian Islands, preferably in shady,
damp forests growing as epiphytes upon trees, and on the banks
of streams. Outside the Tropics few are found. _Acorus calamus_
was introduced into Europe from Asia about 300 years ago; it,
however, never sets any fruit, as the pollen is unfertile. In
England _Arum maculatum_ is a very common plant; this and _A.
italicum_ are the only native species. _Colocasia antiquorum_
comes from Polynesia and the Indian Islands, and also _Alocasia
macrorrhiza_. Fossils in Cretaceous and Tertiary.
USES. Many species have pungent, and even _poisonous properties_
(_e.g. Dieffenbachia_, _Lagenandra_, _Arum_), which are easily
removed by boiling or roasting; the _rhizomes_ of many species
of _Caladium_, _Colocasia_ (_C. antiquorum_, _esculenta_, etc.),
are very rich in starch, and in the Tropics form an important
source of food. An uncommon occurrence in the order is the
highly aromatic rhizome of _Acorus calamus_; this contains
calamus-oil and acorin which are used in perfumery. Many are
ornamental plants, _e.g. Zantedeschia æthiopica_ (South Africa),
generally known as “Calla,” and _Monstera deliciosa_; many other
species are grown in greenhouses.
Order 6. =Lemnaceæ (Duck-weeds).= These are the most reduced form of
the Spadicifloræ. They are very small, free-swimming water-plants.
The vegetative system resembles a small, leaf-like body (Fig. 303
_f-f_), from which roots hang downwards; this branches by producing a
new, similar leaf-like body, which springs from a pocket-like hollow
(indicated by a dotted line in the figure) on each side of the
older one, at its base (or only on one side). ~The branching is thus
dichasial or helicoid (Fig. 303 _A_, where _f, f′, f″, f″′_ indicate
shoots of 1st, 2nd, 3rd, 4th generations respectively). The leaf-like
bodies are, according to Hegelmaier, leaf-like stems, and thus _Lemna_
has no other leaves than the spathe and the sporophylls; according
to the investigations of Engler they are stems whose upper portion
(above the “pocket”) is a leaf, which is not sharply separated from
the underlying stem-portion. The inflorescence is a very much reduced
Araceous-spadix, consisting in _Lemna_ of 1 or 2 stamens of unequal
length (1-stamened ♂-flowers), 1 unilocular carpel (♀-flower), and
1 thin spathe (_B_). [The same is found in _Spirodela polyrrhiza_,
etc., whose daughter-shoots begin in addition with 1 basal-leaf.
_Wolffia arrhiza_, etc., have no roots, no spathe, and only 1 ♂-flower
in the inflorescence (Engler).]--On the germination of the seed a
portion of the testa is thrown off as a lid, so that an exit is opened
for the radicle.--19 species. In stagnant fresh water, both Temp.
and Tropical.--In Europe the species are _Lemna minor, trisulca,
gibba; Spirodela polyrrhiza_, and _Wolffia arrhiza_, the smallest
Flowering-plant.~
[Illustration: FIG. 303.--_Lemna_: _A_ vegetative system; _B_
portion of a plant with flowers; one stamen and tip of the carpel
project; the remaining portions being indicated by the dotted
line.]