Part 25

Order 1. =Juncaginaceæ.= The ☿, regular, _hypogynous_ flowers have the _perianth_ 3 + 3, _sepaloid_, stamens 3 + 3 (with extrorse anthers), and carpels 3 + 3 (free or united), of which last, however, one whorl may be suppressed (in _Triglochin maritima_ all 6 carpels are developed, in _T. palustris_ the inner whorl is unfertile). Inflorescence long spikes. Embryo _straight_.--Marsh-plants with radical, rush-like leaves, arranged in two rows, and often sheathing and ligulate (“squamulæ intravaginales”); the inflorescence is a spike or raceme.--_Scheuchzeria._ Carpels almost free; in each at least two ovules. Follicles.--_Triglochin_ has long, fine racemes without bracts or bracteoles; one ovule in each carpel. The carpels in the two native species are united, but separate when ripe as a schizocarp, loosening from below; they open along the ventral suture or remain closed; a linear central column remains. ~The most reduced is Lilæa (1–2 sp. Am.)--Protogynous. About 10 species. Temp. Fossils in Tertiary.~

Order 2. =Potamogetonaceæ.= The aquatic plants belonging to this order are perennial, living entirely submerged, or with floating leaves, and preferring still water. The leaves are alternate, in some linear and grass-like, in others there is an elliptical floating blade, supported by a linear submerged petiole. Axillary scales. The fruit is generally a syncarp with _nuts_ or _drupes_; the _embryo is curved_, of very various forms.

_Potamogeton_ (Pond-weed). The rhizome is creeping, sympodial (with two internodes in each shoot-generation); the inflorescence is a terminal, many-flowered spike, without floral-leaves; below it are found 2 foliage-leaves placed nearly at the same height, from whose axils the branching is continued cymosely. The flowers are ☿, 4-_merous_, naked, and consist only of 4 _stamens_, with the _connectives, broadly developed_ at the back of the anthers, _resembling a perianth_, and of 4 _free, sessile carpels_. They are common plants in fresh water. ~The spike, during the flowering, is raised above the water. Wind-pollinated and protogynous.--Closely allied is _Ruppia_ (Tassel Pond-weed), in salt or brackish water. The spike has only two naked flowers, each consisting of 2 stamens and 4 carpels. The stalks of the individual carpels are considerably prolonged.--_Zannichellia_ (Horned Pond-weed) is monœcious; the ♀-flower consists of 4 (2–9) carpels, with membranous, bell-shaped perianth; long styles; the ♂-flower has 1 (-2) stamens. _Althenia._~

_Zostera_ (Grass-wrack) is an entirely submerged, marine plant with creeping rhizome (with displacement of buds) and strap-shaped leaves. The flowering shoots are sympodia with displacement of the axes (Fig. 281). The inflorescence is a peculiar, flatly-compressed spike, on _one_ side of which the flowers are borne (Fig. 281). ~This inflorescence may be considered, no doubt correctly, to be derived from the symmetrical spike of _Potamogeton_ by strongly dorsiventral development, and by a strong suppression of the floral parts taking place simultaneously. Two rows of flowers are developed, but of these one is so pressed into the other that apparently only one is present.~ Each flower consists of only 1 stamen and 1 carpel situated at the same height (Fig. 281); the unilocular ovary encloses 1 pendulous ovule and bears a bifid style. As regards the perianth (?) one leaf may be present (_Z. nana_, Fig. 281 _D_). The pollen-grains are filamentous. Pollination takes place under water. ~_Posidonia_ and _Cymodocea_ are allied to these. About 70 species.~

Order 3. =Aponogetonaceæ.= Aquatic plants with tuberous stem. They have a single, petaloid perianth (3–2–1–leaved), most frequently 6 stamens and 3(-6) carpels. Straight embryo.--About 15 species (Africa, Madagascar, Tropical Asia and Australia).--_Aponogeton distachyos_ and _A._ (_Ouvirandra_) _fenestralis_ are grown in conservatories; the latter has lattice-like, perforated leaves.

Order 4. =Najadaceæ.= Only one genus _Najas_ (about 10 species); annual fresh water plants with leaves in pairs and solitary, unisexual flowers. The ♂ flower is remarkable in having a terminal stamen, which has either 4 longitudinal loculi or 1 central one; on this account the stamen of _Najas_ is considered by some authorities to be a stem and not a leaf-structure. The unilocular gynœceum and the single, erect, anatropous ovule are also terminal. Pollination takes place under the water.

Order 5. =Alismaceæ.= The regular, _hypogynous_ flowers are in some species unisexual by the suppression of either andrœcium or gynœceum; they have a 6-merous perianth, _generally_ differentiated into 3 sepals and 3 petals; generally 6 _stamens in the outer whorl_ (by the division of the 3; Fig. 282) and often several 3-merous whorls inside these, and 6–∞ _free_ carpels arranged cyclically or spirally. Fruit a syncarp.--Marsh- or water-plants with radical leaves and long-stalked inflorescences.

=A.= _Butomeæ. Follicles with many seeds, which are borne on nearly the whole of the inner surface of the cyclic carpels_ (as in Nymphæaceæ). Embryo _straight_.--_Butomus_ (Flowering Rush, Fig. 282), has an umbel (generally composed of 3 helicoid cymes). _S_ 3, _P_ 3, stamens 9 (6 + 3, _i.e._ the outer whorl doubled), _G_ 3 + 3. ~_B. umbellatus_; creeping rhizome with triangular Iris-like leaves.--_Hydrocleis. Limnocharis._~

=B.= _Alismeæ._ Fruit achenes. Latex common (in the intercellular spaces). The flowers are arranged most frequently in single or compound whorls. Embryo _curved_, horse-shoe shaped.--_Alisma_ has _S_ 3, _P_ 3, _A_ 6 (in 1 whorl, grouped in pairs, _i.e._ doubled in front of the sepals), and 1 _whorl_ of 1-seeded achenes on a flat receptacle. The leaves are most frequently radicle, long-stalked; the lamina have curved longitudinal veins, and a richly branched venation. _A. plantago._--_Elisma_ (_E. natans_) has epitropous (turned inwards) ovules, whilst the ovules of _Alisma_, _Sagittaria_ and others are apotropous (turned outwards).--_Echinodorus_ (_E. ranunculoides_) has a convex receptacle, carpels many, united and capitate. _Damasonium_.--_Sagittaria_ (Arrow-head) has _monœcious_ flowers, several whorls of stamens and _spirally-arranged achenes_ on a very convex receptacle. ~_S. sagittifolia_ reproduces by tuberous buds formed at the end of long, submerged branches. The leaves, in deep and rapidly running water, are long and strap-shaped, but in the air arrow-shaped.~

Honey is secreted in the flower and pollination effected by insects. _Alisma plantago_ has 12 nectaries. The submerged flowers of _Elisma natans_ remain closed and are self-pollinated. _Butomus_ has protandrous flowers. There are about 50 species, which mostly grow outside the Tropics.--Uses insignificant. The rhizome of some is farinaceous.

Order 6. =Hydrocharitaceæ.= This order differs chiefly from the preceding in its _epigynous_ flowers. These are in general unisexual (_diœcious_), and surrounded by a 2-leaved or bipartite _spathe_; they are 3-merous in all whorls, but the number of whorls is generally greater than 5, sometimes even indefinite. The perianth is divided into _calyx_ and _corolla_. The ovary is _unilocular_ with parietal placentation, or more or less incompletely plurilocular. The fruit is berry-like, but usually ruptures irregularly when ripe. Embryo straight.--Most often submerged water-plants, leaves seldom floating on the surface. Axillary scales (_squamulæ intravaginales_).

_Hydrocharis._ Floating water-plants with round cordate leaves; S3, P3 (folded in the bud); ♂-flowers: 3 (-more) flowers inside each spathe; stamens 9–15, the most internal sterile. ♀-flowers solitary; three staminodes; ovary 6-locular, with many ovules attached to the septa; styles 6, short, bifid. [The petals of the ♀-flowers bear nectaries at the base. In this and the following genus the pollination is without doubt effected by insects.] ~_H. morsus ranæ_ (Frog-bit) has runners; it hibernates by means of special winter-buds.~--_Stratiotes_; floating plants with a rosette of linear, thick, stiff leaves with spiny margin, springing from a short stem, from which numerous roots descend into the mud. Inflorescence, perianth, and ovary nearly the same as in _Hydrocharis_, but the ♂-flower has 12 stamens in 3 whorls, of which the outer 6 are in 1 whorl (dédoublement), and inside the perianth in both flowers there are numerous (15–30) nectaries (staminodes?). _S. aloides_ (Water-soldier); in N. Eur. only ♀-plants.--~_Vallisneria spiralis_ is a tropical or sub-tropical plant, growing gregariously on the mud in fresh water. The leaves are grass-like, and the plants diœcious; the ♂-flowers are detached from the plant, and rise to the surface of the water, where they pollinate the ♀-flowers. These are borne on long, spirally-twisted peduncles which contract after pollination, so that the ♀-flower is again drawn under the water, and the fruits ripen deeply submerged.--_Elodea canadensis_ is also an entirely submerged plant. The leaves are arranged in whorls on a well-developed stem. Only ♀-plants in Europe (introduced about 1836 from N. Am). This plant spreads with great rapidity throughout the country, the reproduction being entirely vegetative. _Hydrilla_, _Halophila_, _Thalassia_, _Enhalus_.--In many of these genera the number of whorls in the flower is remarkably reduced; for example, in _Vallisneria_, in the ♂-flowers to 2: Pr 3, A (1-) 3, in the ♀ to 3: Pr 3, Staminodes 3, G 3.--About 40 species; Temp. and Trop.~

Family 2. =Glumifloræ.=

The _hypogynous_ flowers in the Juncaceæ are completely developed on the _pentacyclic, trimerous_ type, with _dry, scarious perianth_. Even in these the interior whorl of stamens becomes suppressed, and the ovary, which in _Juncus_ is trilocular with many ovules, becomes in _Luzula_ almost unilocular, but still with 3 ovules. The perianth in the Cyperaceæ and Gramineæ is reduced from hairs, in the first of these, to nothing, the flowers at the same time collecting more closely on the inflorescence (spike) supported by _dry_ bracts (_chaff_); the number of stamens is almost constantly 3; stigmas linear; the ovary has only 1 loculus with 1 ovule, and the fruit, which is a capsule in the Juncaceæ, becomes a nut or caryopsis.--The endosperm is large and floury, the embryo being placed at its lower extremity (Figs. 286 _B_, 291).--The plants belonging to this order, with the exception of a few tropical species, are annual or perennial herbs. The stems above ground are thin, and for the most part have long internodes, with linear, parallel-veined leaves which have long _sheaths_, and often a _ligule_, _i.e._ a membranous projection, arising transversely from the leaf at the junction of the sheath and blade. The underground stems are short or creeping rhizomes. The flowers are small and insignificant. Wind- or self-pollination.

Order 1. =Juncaceæ= (=Rushes=). The regular, hermaphrodite, hypogynous flowers have 3 + 3 brown, dry, free perianth-leaves projecting like a star during the opening of the flower; stamens 3 + 3 (seldom 3 + 0) and 3 carpels united into one gynœceum (Fig. 283); the ovary is 3- or 1-locular; there is as a rule 1 style, which becomes divided at the summit into 3 stigmas, often bearing branches twisted to the right (Fig. 283). _Fruit a capsule_ with loculicidal dehiscence. The embryo is an extremely small, ellipsoidal, cellular mass, without differentiation into the external organs.

_Juncus_ (Rush) has glabrous foliage-leaves, generally cylindrical, rarely flat; the edges of the leaf-sheath are free (“_open_” leaf-sheaths) and cover one another. The capsule, 1- or 3-locular, with _many_ seeds--_Luzula_ (Wood-Rush) has flat, grass-like leaves with ciliated edges; the edges of the leaf-sheath are united (“_closed_” leaf-sheath). The capsule unilocular and _3-seeded_.--_Prionium_: S. Africa; resembling a _Tacona_.

The _interior_ whorl of stamens, in some species, disappears partially or entirely (_J. supinus_, _capitatus_, _conglomerates_, etc.)

Some of the numerous _Juncus_-species (_e.g. J. effusus_, _glaucus_, _conglomeratus_, etc.), have false, lateral inflorescences, the axis of the inflorescence being pushed to one side by its subtending leaf, which apparently forms a direct continuation of the stem, and resembles it both in external and internal structure. The foliage-leaves of this genus were formerly described as “unfertile stems,” because they are cylindrical, erect, and resemble stems, and consequently the stem was said to be “leafless”: _J. effusus_, _glaucus_, _conglomeratus_. Stellate parenchynatous cells are found in the pith of these stems and in the leaves. Other species have distinct terminal inflorescences and grooved leaves; _J. bufonius_ (Toad-rush), _compressus_, and others. The _inflorescences_ most often present the peculiarity of having the lateral axes protruding above the main axis. Their composition is as follows:--The flowers have either no bracteoles, and the inflorescences are then capitulate; or they have 1–several bracteoles. Each branch has then, first, a 2-keeled fore-leaf placed posteriorly (“basal-leaf”), and succeeding this are generally several leaves borne alternately and in the same plane as the basal-leaf, the two uppermost (the “spathe-leaves”) being always barren; those which lie between the basal-leaves and the spathe-leaves are termed “intermediate-leaves.” If only branches occur in the axils of the basal-leaves, then the succeeding branches are always borne on the posterior side of the axis, and form a fan[27]; if the basal-leaf is barren, and if there is only one fertile intermediate-leaf, then the lateral axes are always on the upper side, and a sickle[27]-like inflorescence occurs; if there are 2 fertile intermediate-leaves, then a dichasium is formed, and in the case of there being several, then a raceme, or spike.

_Juncaceæ_ are, by several authors, classed among the Liliifloræ, but there are so many morphological and partly anatomical features agreeing with the two following orders, that they may, no doubt, most properly be regarded as the starting point of these, especially of the _Cyperaceæ_, which they resemble in the type of flowers, the inflorescence, the type of mechanical system, and the stomata.

POLLINATION by means of the wind. Cross-pollination is often established by protogyny. _J. bufonius_ has partly triandrous and cleistogamic, partly hexandrous, open flowers.--DISTRIBUTION. The 200 species are spread over the entire globe, but especially in cold and temperate countries; they are seldom found in the Tropics.--USES. Very slight; plaiting, for instance.

Order 2. =Cyperaceæ.= The majority are _perennial_ (seldom annual) _herbs_ living in damp situations, with a sympodial rhizome and grass-like appearance. The stems are seldom hollow, or have swollen nodes, but generally _triangular_, with the upper internode just below the inflorescence generally very long. The leaves are often arranged in 3 _rows_, the leaf-sheath is _closed_ (very seldom split), and the ligule is absent or insignificant. The flowers are arranged in _spikes_ (_spikelets_) which may be united into other forms of inflorescences (chiefly spikes or racemes). The flowers are supported by a bract, but have _no bracteoles_. In some genera the perianth is distinctly represented by six bristles corresponding to six leaves (Figs. 284 _A_, 286 _A_); in others it is represented by an indefinite number of hairs (Fig. 284 _B_), and very frequently it is altogether wanting. _The inner whorl of stamens is absent_, and the flower has therefore 3 stamens (rarely more or less than 3), the anthers _are attached by their bases to the filament_ (innate) and are not bifid (Figs. 286). Gynœceum simple, formed of 3 or 2 carpels; 1 style, which is divided at the extremity, as in the Juncaceæ, into 3 or 2 arms; the single loculus of the ovary contains one basal, erect, anatropous ovule; the stigmas are not feather-like. _Fruit a nut_, whose seed is generally not united with the pericarp. The embryo is small, and lies at the _base of the seed in the central line_, surrounded on the inner side by the endosperm (Fig. 286 _B_). On germination the cotyledon _does not remain_ in the seed.

A regular perianth, with 6 scale-like perianth-leaves in 2 whorls, is found in _Oreobolus_. In _Scirpus littoralis_ the perianth-leaves are spreading at the apex, and divided pinnately.

The branching of the inflorescence is often the same as in the Juncaceæ, and supports the theory that these two orders are related. In _Rhynchospora_ and others, the “spikelets” are really only “spike-like” and to some extent compound.

=A.= SCIRPEÆ. HERMAPHRODITE FLOWERS.

1. Spikelets cylindrical, the bracts arranged spirally (in many rows). The lower ones are often barren, each of the others supports a flower.--_Scirpus_ (Club-rush). The spikelets are many-flowered; the perianth is bristle-like or absent, and does not continue to grow during the ripening of the fruit (Fig. 286 _A_). Closely allied to this is _Heleocharis_, with terminal spikes.--_Eriophorum_ (Cotton-grass) differs chiefly in having the perianth-hairs prolonged, and forming a bunch of white, woolly hairs (Fig. 284 _B_).

_Cladium_ and _Rhynchospora_ (Beak-rush) differs especially in the _few_-flowered, compound spikelets which are collected into small bunches; the latter has received its name from the fact that the lowermost portion of the style remains attached to the fruit as a beak.

2. Spikelets compressed, the bracts arranged only in _two rows_; the other characters as in the first-mentioned. _Cyperus_ (spikelets many-flowered); _Schœnus_ (Bog-rush); spikelets few-flowered; _S. nigricans_ has an open sheath.

=B.= CARICEÆ. UNISEXUAL FLOWERS.

In the ♂-flowers there is no trace of a carpel, and in the ♀ no trace of a stamen. Floral-leaves in many rows. In some (_Scleria_, certain _Carex_-species), ♂-and ♀-flowers are borne in the same spikelet, the latter at the base or the reverse; in the majority each spikelet is unisexual.

_Carex_ (Fig. 285) has _naked_, most frequently monœcious flowers. The ♂-_spikes_, which are generally placed at the summit of the whole compound inflorescence, are _not compound_; in the axil of each floral-leaf (bract) _a flower is borne, consisting only_ of a short axis with three stamens (Fig. 285 _A_). The ♀-_spikes are compound_; in the axil of each floral-leaf is borne a very small branch (Fig. 285 _D_, _a_) which _bears only one leaf_, namely, a _2-keeled fore-leaf_ (_utriculus_, _utr._ in the figures) which is turned posteriorly (as the fore-leaves of the other Monocotyledons), and being obliquely sheath-like, envelopes the branch (in the same manner as the sheath of the vegetative leaves), and forms a pitcher-like body. In the axil of _this_ leaf the ♀-flower is situated as a branch of the 3rd order, bearing only the 2–3 carpels, which are united into one gynœceum. The style protrudes through the mouth of the utriculus. ~The axis of the 2nd order (_a_ in Fig. 285 _D_) may sometimes elongate as a bristle-like projection (normally in _Uncinia_, in which it ends as a hook, hence the name); this projection is in most cases barren, but it sometimes bears 1–several bracts which support male-flowers; this is normal in _Elyna_ (or _Kobresia_) and _Schœnoxiphium_; the axis (_a_ in 285 _E_) bears at its base a female-flower supported by the utriculus, and above it a male-flower supported by its bract.~

POLLINATION by means of the wind. Protogynous. Sometimes self-pollinated. The order embraces nearly 3,000 species, found all over the world. _Carex_ and _Scirpus_ are most numerous in cold and temperate climates, and become less numerous towards the equator. The reverse is the case with _Cyperus_ and other tropical genera. They generally confine themselves to sour, swampy districts; some, on the other hand, are characteristic of sand-dunes, such as Sand-star (_Carex arenaria_). There are about 70 native species of _Carex_.

USES. In spite of their large number, the Cyperaceæ are of no importance as fodder-grasses, as they are dry and contain a large amount of silica; hence the edges of many of the triangular stems or leaves are exceedingly sharp and cutting. _Cyperus esculentus_ has tuberous rhizomes, which contain a large amount of fatty oil and are edible (earth-almonds); it has its home in the countries of the Mediterranean, where it is cultivated.

_Cyperus papyrus_ (W. Asia, Egypt, Sicily) attains a height of several metres, and has stems of the thickness of an arm which were used by the ancient Egyptians for making paper (papyrus). Some serve for plaiting, mats, etc. (_Scirpus lacustris_, etc.). _Isolepis_ is an ornamental plant.