Fig. 553.—Cuscuta trifolii, parasitic on Red Clover. A A portion of the stem with an inflorescence and haustoria (mag.); B seed (nat. size); C seed (mag.); D embryo (nat. size).
840 species; the majority in the Tropics, especially Am. Many are ornamental plants. Officinal: some on account of their purgative properties: the tuberous roots of Ipomæa purga (Jalap, from Mexico) and the dried latex (“Scammony”) of Convolvulus scammonia (from the East). The tuberous roots of Batatas edulis (Trop. S. Am.) are used as a common vegetable (Sweet Potato) in the Tropics.
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.
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.
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 (f1 and f2), 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 (f1) of the two leaves on each shoot is barren, and is therefore not displaced; but the upper one (the second bracteole, f2) is displaced as in the first instance, and consequently it assumes a position near the first leaf (the shaded leaf f2 of shoot I being placed near the white leaf f1 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.
Fig. 556.—Diagrammatic representation of the branching in Solanaceæ. The various shoot-generations are white or shaded.
Fig. 557.—Fruit of Hyoscyamus niger after removal of calyx.
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).
Figs. 559–561.—Solanum tuberosum.
Fig. 559.—Flower (1/1).
Fig. 560.—Stamen, ejecting pollen.
Fig. 561.—Longitudinal section of seed.
B. Fruit a berry. Solanum (Nightshade); rotate corolla (Fig. 559). The stamens have short filaments, the anthers stand erect, close together round the style, like a cone in the centre of the flower, and open by pores at the apex (Fig. 560). S. tuberosum (the Potato-plant); the Potato-tuber is a swollen, underground stem; the “eyes” are buds, situated in the axils of its scale-like, quickly-perishing leaves.—Lycopersicum resembles Solanum in the flower, but the united anthers open by longitudinal clefts and have an apical appendage. The cultivated species, L. esculentum (Tomato), has often a higher number than 5 in the flower, and in the fruit several loculi of unequal size.—Physalis (Winter Cherry); the calyx ultimately swells out in the form of a bladder, becomes coloured, and loosely envelopes the spherical berry.—Capsicum (Guinea Pepper-plant); some species have very large, irregular, rather dry (red, yellow, black) berries, which are unilocular in the upper part.—Lycium (false Tea-plant); the corolla is salver- or funnel-shaped; shrubs; often thorny.—Atropa (A. belladonna, Deadly Nightshade, Fig. 555); corolla campanulate; the calyx projects beneath the spherical, black berry. The flowers are borne singly.—Mandragora; (Mandrake); Nicandra (ovary often 5-locular).—A small tropical group: Cestreæ (Cestrum, Habrothamnus, etc.) has an almost straight embryo, which may also be found e.g. in species of Nicotiana. Related to the Scrophulariaceæ.
About 1,500 species; the majority within the Tropics, outside these limits especially in America. Solanum nigrum is a common weed.—The Potato-plant (Solanum tuberosum), from Peru and Chili, was introduced into Europe in 1584 by Sir Walter Raleigh. (Potatoes = Batatos). The fruits of several serve as condiments: Chilies or Pod-pepper (Capsicum annuum and longum), and the Cayenne-pepper (C. baccatum and others), whose fruits also are officinal, were brought to Europe from S. America by Columbus, and are commonly cultivated in Tropical America; Lycopersicum esculentum (Tomato) and others from Peru; Solanum ovigerum (Egg-plant); Solanum melongena, etc. Poisonous, acrid, narcotic properties (alkaloids, etc., solanine, nicotine, atropine, hyoscyamine) are found in many: Atropa belladonna (from S. Europe; the roots and leaves are officinal); Solanum dulcamara (Bitter-sweet; formerly officinal), S. toxicarium (Guiana); Datura stramonium from Asia (leaves and seeds officinal), D. sanguinea, metel, tatula, and others; Hyoscyamus (officinal: the leaves and seeds of H. niger); Nicotiana tabacum (Virginian tobacco, officinal: the leaves), N. rustica and others from Trop. America (Tobacco was introduced into Europe in 1560); Cestrum-species. Duboisia myoporoides (Australia); the leaves contain hyoscyamine and are used in medicine. A number of species of these genera are ornamental plants.
Order 2. Nolanaceæ. These most resemble the Convolvulaceæ in the corolla, but the Solanaceæ in their branching, and leaf-arrangement (in pairs, etc.). The diagram is the same as in Nicandra with 5 carpels, but the fruits of this order most frequently form, by invaginations in various directions, an ovary (with 1 style) consisting of numerous and irregularly grouped, 1-ovuled cells; the fruit is a schizocarp with many 1-seeded fruitlets.—Nolana (Western S. America): a few are ornamental plants.
Order 3. Scrophulariaceæ. The flower is hypogynous, ☿, zygomorphic, with the usual type: S5, P5, A5, and G2, the latter placed in the median plane; some genera have all 5 stamens developed (Fig. 562 A), but most frequently the posterior one is suppressed and the flower becomes didynamous (Fig. 562 B). The fruit, as in the capsular-fruited Solanaceæ, is a bilocular, 2-valved capsule, with a thick, axile placenta, and most often septicidal dehiscence (Fig. 563 C). The numerous seeds are not reniform as in many Solanaceæ, and have a straight, or only slightly curved embryo, with abundant endosperm (Fig. 563 D).—The majority are herbs; some are arborescent; the leaves are opposite or scattered, but stipules are wanting as in the whole family.
The Scrophulariaceæ are closely allied to the Solanaceæ, and there is, properly speaking, no characteristic feature which absolutely separates them. The somewhat irregular corolla, with five stamens of unequal length in Verbascum, is also found in Hyoscyamus; curved and straight embryos are found in both orders. The activation of the corolla in the Scrophulariaceæ is simple imbricate, in the Solanaceæ most frequently folded imbricate (in Atropa and those allied to it, imbricate without folding). The genera (about 164) are distinguished according to the form of the corolla, number of stamens, inflorescence, arrangement of the leaves, etc. Verbascum belongs to the most primitive 5-stamened forms, and from it proceed a long series down to Veronica, with only two stamens and most frequently the posterior sepal suppressed.
Fig. 562.—Diagrams. A Verbascum; B Linaria; C Veronica.
1. Antirrhineæ, Snapdragon Group. This has most frequently a descending æstivation of the petals (the posterior petals are outside the lateral ones, which again enclose the anterior; Fig. 562 A, B). The plants belonging to this group are not parasites.
a. 5-stamened.—Verbascum (Mullein, Fig. 563 A) has a slightly irregular, rotate corolla; five stamens (frequently covered with woolly hairs), of which the two anterior ones are the longer and differ often also in other respects. The inflorescences are racemose, often with several series of accessory dichasia in the axil of each primary floral-leaf. The leaves are scattered and, together with the stems, are often covered with a grey felt of branched hairs.
Fig. 563.—Verbascum thapsiforme.
Fig. 564.—Antirrhinum majus. A flower, and the upper lip of a flower with the stamens.
Fig. 565.—Scrophularia nodosa. Protogynous flower in various stages: A ♀ stage; g the stigma projecting from the throat of the corolla; B the same in longitudinal section; C ♂ stage, the stigma is bent down and its former position occupied by the stamens; s staminode; g stigma; d nectary.
Fig. 566.—Digitalis purpurea.
b. 4-stamened, didynamous (Fig. 564).—Scrophularia (Fig-wort, Fig. 565) has cymose inflorescences in a panicle; the corolla (Fig. 565) is urceolate, short two-lipped; the posterior stamens are present as a scale below the upper lip of the corolla (Fig 565 s). S. nodosa has a tuberous rhizome.—Pentstemon; the posterior stamen is barren and very long.—Antirrhinum (Snapdragon). The corolla (Fig. 564) is personate, i.e. bilabiate, but with the under lip arched to such an extent that it meets the upper lip, closes the corolla throat, and entirely conceals the stamens and style; the corolla-tube is produced into a short pouch at the base on the anterior side. The capsule is oblique and opens by 2–3 pores, formed by small, dentate valves. In Linaria (Toad-flax) the pouch is produced into a spur. Sometimes there are traces of the posterior stamens. The capsule opens by large pores (one for each loculus), produced by large, many-partite valves. L. vulgaris reproduces by suckers.—Digitalis (Foxglove, Fig. 566) has long racemes with drooping flowers; the posterior sepal is small (a step towards complete suppression, as in Veronica); the corolla is obliquely campanulate, and generally nearly 4-lobed, the two posterior petals coalescing.—Alonsoa; Nemesia; Chelone; Herpestis; Mimulus; Torenia; Vandellia; Limosella (L. aquatica, Mud-wort, native); Scoparia; Capraria; Erinus (found on the Roman Camp at Chesters, Northumberland, and supposed to have been introduced from Spain by the Roman soldiers); Celsia (near Verbascum); Maurandia; Lophospermum; Rhodochiton; Collinsia; Nycterinia, etc.
Fig. 567.-Flower of Veronica.
c. 2-stamened.—Gratiola (Water-hyssop). 5-partite calyx. The upper lip of the corolla is undivided or slightly bifid; the two anterior stamens are either entirely absent or are reduced to staminodes (a transition to Veronica).—Veronica (Speedwell), most frequently 4-partite calyx; 4-lobed, rotate, zygomorphic corolla with 2 perfect stamens and no trace of the others (Figs. 567, 562 c); capsule with loculicidal dehiscence. Calceolaria; the corolla has two slipper-like lips.
2. Rhinantheæ, Yellow-rattle Group. Herbs, all of which (with the exception of Lathræa) are annual parasites with green foliage-leaves. They attach themselves by haustoria to the roots of other plants and draw nourishment from them. The majority turn black when dried. Racemose inflorescences. In many the calyx is 4-partite, the posterior sepal being absent, or very small. The corolla is distinctly bilabiate (Fig. 568), with most frequently ascending æstiration; in the majority it does not become detached at the base, but by means of a ring-like cut some distance up the tube; 4 didynamous stamens; pollen-grains dry, easily falling out; the anthers are often furnished at the base with bristles or hairs (Fig. 568) which play a part in the pollination, the probosces of the insects, being forcibly pushed against them, agitate the anthers and shake out the pollen-grains. Capsule with loculicidal dehiscence.—Euphrasia (Eye-bright), Melampyrum (Cow-wheat), Rhinanthus (Yellow-rattle), Odontites (Bartsia), Pedicularis (Louse-wort), and Lathrœa (Tooth-wort) all have native species. The last named is pale yellow, or reddish (without chlorophyll); it is a parasite on the roots of the Hazel, Beech and other shrubs, having an aerial stem, and an underground, perennial rhizome, covered with opposite, scale-like, more or less fleshy leaves with a number of internal glandular, labyrinthine cavities. The inflorescence is a unilateral raceme. It approaches Gesneriaceæ in having a unilocular ovary with two parietal placentæ.
Fig. 568.—Euphrasia officinalis. Flower of the large and the small-flowered forms; showing the anthers and stigmas.
The mechanical contrivances for POLLINATION are so numerous that no general principle can be laid down. Personate flowers, like those of Antirrhinum are only accessible to strong insects, such as humble-bees, which can force themselves between the two lips, and so become dusted with pollen on the back. In Euphrasia and other Rhinantheæ the insects become covered with smooth, powdery pollen when they shake the anther-apparatus in touching the hairs and bristles mentioned above. Scrophularia nodosa is protogynous (Fig. 565). Digitalis purpurea, however, is protandrous. Mimulus luteus and some others have sensitive stigmatic lobes, which shut up on being touched. The Veronica-species constitute a series, from large-flowered down to small-flowered forms, and parallel with them are found various gradations from insect-to self-pollination. In some (as Euphrasia officinalis, Rhinanthus crista galli) there are two kinds of flowers: large, which are pollinated by insects, and small, which are self-pollinated (Fig. 568). Lathræa squamaria (Tooth-wort) is a protogynous spring-flowering plant, largely visited by humble-bees. Others have cleistogamic flowers. Nycterinia capensis opens its flowers at night.
2,000 species; chiefly from the Temp. Officinal: Digitalis purpurea (the leaves; Europe), a poisonous plant. Verbascum thapsus and thapsiforme, Veronica officinalis (“Herba V.”), Gratiola officinalis (“Herba”) have medicinal uses. The whole of the Scrophulariaceæ are more or less suspicious, if not actually poisonous, and none serve as food. Many are ORNAMENTAL PLANTS: Mimulus luteus (N. America), Paulownia imperialis (the only species; in Japan; a tree), Antirrhinum vulgare (S. Eur.), Linaria, Pentstemon, Veronica, Calceolaria (Peru, Chili, etc.).
Fig. 569.—Leaf of Utricularia vulgaris, with bladder. Median longitudinal section through a bladder containing a Cyclops. At a a hair of the upper-lip, at i 2 bristles of the under-lip of the entrance (a, b); in the latter are placed 4 bristles h; k stalk of the bladder, in which is seen a vascular bundle. (After Cohn.)
Order 4. Utriculariaceæ. To this order belong only perennial, insectivorous, aquatic, and marsh-plants (200 species) with a more or less characteristic appearance. They differ from the Scrophulariaceæ, especially in having 2 stamens (the anterior) and a unilocular ovary, with free, central placenta (like that of the Primulaceæ). For the rest the flower is distinctly bilabiate, both in the calyx and corolla. Two-valved capsule; no endosperm.
Pinguicula (Butter-wort) has a rosette of leaves close to the ground; these are sticky, covered with glandular hairs, and roll round any small insects which may be caught upon them; flowers solitary, terminal on a long scape; calyx, 5-partite; corolla with spur. The embryo germinates with 1 cotyledon.—Utricularia (Bladder-wort). Our native species are floating, without roots, with hair-like, divided leaves, studded with peculiar bladders (in the Tropics there are terrestrial species, with ordinary foliage). The bladders (Fig. 569) have an aperture, closed by a valve opening inwards, so that small aquatic animals are allowed to enter, but are not able to escape; they are thus entrapped in the bladders, and are probably used as food. Calyx bipartite; corolla personate with spur.
The embryo of Utricularia is very imperfect, scarcely more than a spherical, cellular mass, with a few slight leaf-rudiments. On the germination of U. vulgaris, several bristle-like leaves develop into a compact rosette; the stem then develops, and also the finely-divided, bladder-bearing leaves. A primary root is not developed. The stems branch copiously and in a very peculiar manner. The growing-point of the stem is rolled spirally.—The stigmatic lobes are sensitive and close on being touched; self-pollination often takes place, however, in Pinguicula.
Order 5. Gesneriaceæ. The flower in this order may be both epigynous (Gesnerieæ) and hypogynous (Cyrtandreæ), but otherwise is nearly the same as in Scrophulariaceæ, only that the ovary is unilocular, with 2 parietal, often bifid, placentæ. Of the 5 stamens the posterior is rudimentary, or (more rarely) entirely wanting, and the others are didynamous (Cyrtandreæ have often only 2 stamens); their anthers are generally glued into a quadrangular mass. The majority are herbs with juicy stems, opposite, verticillate or scattered leaves without stipules, often, like the stems, thick and juicy, soft-haired or glabrous. The corollas are often highly-coloured (scarlet, red-yellow, etc., and spotted internally), large and magnificent, so that many species are ornamental plants. Gesnerieæ (often epigynous) have endosperm; S. Am.—Cyrtandreæ, hypogynous, without endosperm; Asia, S. Africa.—Streptocarpus, neither the primary root nor primary shoot attains development; one of the cotyledons dies, while the other grows and becomes a very large foliage-leaf, from which spring adventitious roots and adventitious inflorescences.
500 species. Gloxinia, Achimenes, Gesneria, Alloplectus, Tydæa, Columnea, Nægelia, Æschynanthus, and others, especially in the forests of tropical America. Some are epiphytes on trees, others prefer the leaf-mould of the forest and crevices of cliffs. Several genera have peculiar, catkin-like, underground shoots, with scale-like compact leaves; others have tubers.
Orobanche (Broom-rape) is allied to this order as a parasitic form. It is a parasite on the roots of other plants, not like Lathræa by means of thin rootbranches with haustoria, but growing with the base of its stem in close contact with its host, and probably even often protruding a kind of thallus into it, in a manner similar to the Loranthaceæ. Its aerial shoots are not entirely destitute of chlorophyll, but are not green; they only bear scale-leaves and terminate in a raceme or spike-like inflorescence.—Some Orobanche-species are detrimental to various cultivated plants (Hemp, Lucerne, Tobacco, etc.). The flowers are strongly zygomorphic; the posterior sepal is often wanting, and the anterior are united to the two lateral ones. Ovary unilocular, as in Gesneraceæ, with 2 or 4 parietal placentæ.—The exceedingly small seeds have a very rudimentary embryo, formed of an ellipsoidal, cellular mass, without indication of cotyledons or other organs.—About 100 species; especially in the Mediterranean region.
Order 6. Bignoniaceæ. 500 species; nearly all trees and shrubs, and to a great extent lianes, climbing by tendrils (modified leaves), which are sometimes terminated by a special clasping apparatus. These lianes have, as a rule, an anomalous stem structure, the wood being either divided into four wedges at right angles to each other, separated by four grooves filled with secondary wood-parenchyma, or a greater number of wedges occur, by the cambium ceasing to form wood in several places. The leaves are most frequently opposite and compound; the flowers in the main are similar to the didynamous Scrophulariaceæ, and especially resemble those of Digitalis purpurea; they are bilabiate, large, and beautiful, campanulate or trumpet-shaped, many of the prettiest ornamental plants in the Tropics belonging to this order. The fruit is most frequently a large, woody, 2-valved, siliqua-like, septifragal capsule, whose valves separate from the flat and broad partition-wall, which bears the large, generally winged seeds: Tecoma; Bignonia.—In gardens: Catalpa syringæfolia (Trumpet-wood); Tecoma radicans (from S. Am.).—“Palisander”-wood is from Jacaranda (S. Am.).—Eccremocarpus (N. Am.) forms, by its unilocular capsule, a transition to the Gesneriaceæ (E. scaber; herbaceous).
Crescentia is allied to this order; C. cujete (Calabash) is its best known species. The fruit (unilocular with 2 parietal placentæ) is a very large, spherical or ellipsoidal berry, with a firm, finally woody outer layer. After the removal of the juicy interior, these are commonly used as drinking vessels in Tropical America.
Order 7. Pedaliaceæ. Sesamum (orientale and indicum); very important oil-plants, which from olden times have been cultivated in tropical Asia and Africa for food and as medicinal plants, and are now cultivated in America also. The seeds are used as a raw material in the manufacture of soap in Europe.—To this order also belong Martynia and Craniolaria, which have a long horned capsule and sensitive stigmas.—46 species.
Order 8. Acanthaceæ. 1,500 species; mostly erect, slender, branched herbs or shrubs, rarely arborescent, especially in S. Am. and Ind. The branches frequently have swollen nodes; the leaves are opposite, penninerved, undivided, more or less lanceolate or elliptical, and generally leave a distinct scar when they fall off. Stipules are wanting. The flowers are solitary or in dichasia, which are arranged in 4-rowed spikes or racemes, each flower with its subtending bract, which may be brightly coloured, and most frequently also with two bracteoles. With regard to the corolla (which is often labiate, in any case irregular, and frequently prettily coloured), the 2 or 4 didynamous stamens (of whose anthers one half is inserted lower than the other, or suppressed) and the gynœceum, the Acanthaceæ are true Personatæ, approaching most nearly to the Scrophulariaceæ: they differ from the other orders especially in the fruit, which is a bilocular, 2-valved, often elastically dehiscing capsule, which never has more than 2 rows, and in some only 2 seeds in each loculus, the seeds being often compressed and borne on strong, curved or hook-like funicles (retinacula) which persist after dehiscence. Embryo curved without endosperm; radicle pointed downwards.—Cleistogamic flowers are found in several species. Cystoliths are common.
The following grow wild in Europe: Acanthus (spinosus and mollis, whose pinnatifid leaves served as models for the capitals of the Corinthian columns). The posterior sepal is the largest of all the leaves of the flower, and covers the other parts like a helmet; the 2 anterior sepals are united, and the two lateral ones are small and greenish; the corolla has no upper-lip, but only a 3-lobed under-lip. The anthers are bilocular; the filaments ultimately become very firm.—Justicia, Eranthemum, Goldfussia, Thunbergia (a twiner), Ruellia, Dicliptera, etc.—Ornamental plants in conservatories.
Order 9. Plantaginaceæ (Plantains). The flowers (Figs. 570, 571) are regular, ☿, hypogynous, with a 4-partite, persistent calyx, a gamopetalous, scarious corolla with 4 projecting lobes, 4 stamens, incurved in the bud, later on projecting considerably, about equal in length, and a bilocular ovary with one long, filamentous, undivided, feathery, papillose style (see Fig. 571). The ovary is most frequently bilocular with 1–few ovules in each loculus. An hypogynous disc is wanting. The fruit is a pyxidium with 1–few peltate seeds attached in each loculus (Littorella is in several respects an exception). All species are herbs, the majority with leaf-rosettes near the ground, and the flowers in spikes or capitula.
The labiate-like flowers are in this case entirely concealed under a regular, apparently 4-merous exterior. The structure of the flower, however, is the same as in the Scrophulariaceæ, only the reduction, which is found in Veronica (compare Figs. 562 C, 567 with 570, 571), is also present in this instance and the lobes are also more equally developed; the posterior petal corresponds to the bilobed upper-lip; the posterior stamen and the posterior sepal also are entirely wanting. In the development of the flower there is no trace of posterior sepal or stamen, and the posterior petal arises from one primordium, but the two anterior sepals arise before the lateral ones. The position of sepals and petals does not agree with that of a true 4-merous flower, which is represented in Fig. 361 E. The bracteoles are always suppressed in Plantago.
Plantago (Plantain, Rib-grass). The foliage-leaves are most frequently scattered, entire, with curved veins, arranged in a rosette close to the ground on an unlimited rhizome; the spike-like inflorescence is borne on a long scape; in some (P. psyllium) the leaves are opposite on a stem with well-developed internodes, and the inflorescences are borne in their axils. The order also presents a transition from insect-pollinated to wind-pollinated flowers. The flowers are protogynous, wind-pollinated in P. major and P. lanceolata, partly also in the other species, but insect pollination also occurs, and P. media has three kinds of flowers, some of which are adapted for wind-pollination (Fig. 571), others, with short filaments, for insects. Littorella lacustris (Shore-weed) is the most reduced of the Plantaginaceæ: an aquatic plant with rosettes of round, awl-like leaves and diclinous (monœcious) flowers. In the axils of the foliage-leaves is a very short 3-flowered spike, formed by 2 sessile ♀-flowers, and above them a long-stalked ♂-flower; all the flowers are lateral, the terminal one being absent, as in Plantago. The ♂-flower is essentially the same as in Plantago, but the ♀-flower has a scarious corolla, with a narrow, 3–4-dentate mouth, which closes tightly round the nut-like fruit.
Figs. 570, 571.—Plantago media.
Fig. 570.—Diagram of Plantago media.
Fig. 571.—Two different forms of the flower (magnified): 1, chiefly adapted for pollination by wind; 2, for insect-pollination. a The stigma; b the calyx; k the corolla.
The genus Plantago constitutes nearly the entire order (200 species). Some are widely distributed weeds (e.g. P. major, “The white man’s footstep”). In P. psyllium (S. Eur.) the integument of the seeds is mucilaginous, and swells considerably in water.
The flowers are hypogynous and zygomorphic (in Boraginaceæ and Cordiaceæ, however, they are regular, except Echium and Anchusa arvensis). The calyx is gamosepalous, the corolla bilabiate (except in the two orders mentioned), mostly after 2/3, i.e. divided into a 2-leaved posterior portion, and a 3-leaved anterior portion. The æstivation of the corolla is nearly always descending.—In Boraginaceæ and Cordiaceæ there are 5 stamens of equal length; in the other orders 4 didynamous ones, or only 2 fertile; the posterior stamen is sometimes developed as a staminode, sometimes fertile (in Stilbaceæ). The ovary is formed of 2 median carpels (except some Verbenaceæ), with (1-) 2 ovules on each carpel; in the majority of the orders it is, however, divided by a false partition-wall between the dorsal and ventral sutures, into 4 loculi, each of which is often raised independently, causing the style to be situated in the depression between the four lobes (“gynobasic” style, Figs. 572, 573, 575, 579). The fruit in these orders most frequently becomes a 4-partite schizocarp with nut-like fruitlets. The other orders have a 1(-2)-locular ovary.—The leaves are simple, without stipules.
The family is related to (and proceeds from) the Tubifloræ, especially Convolvulaceæ, which has an almost similar construction of the ovary. It is doubtful whether the Cordiaceæ and Boraginaceæ should be classed with the others.
The orders are: 1, Cordiaceæ; 2. Boraginaceæ; 3, Verbenaceæ; 4, Labiatæ; 5, Selaginaceæ; 6. Globulariaceæ; 7, Stilbaceæ.
Order 1. Cordiaceæ unites Convolvulaceæ and Boraginaceæ. Tree-like plants with 5-(4–10) merous flowers, doubly bifid style, and drupe with 4 or less loculi. No endosperm; cotyledons folded.—185 species; tropical.
Order 2. Boraginaceæ. The vegetative parts are very characteristic: herbs with cylindrical stems and scattered, undivided, nearly always sessile, entire leaves, without stipules, and generally, together with the other green portions of the plant, covered with stiff hairs, consequently rough and often even stinging (hence the other name for the order Asperifoliæ). The inflorescences are unipared scorpioid cymes with the branches coiled spirally (“helicoid,” Fig. 573) before the flowers open. The flower is perfect, regular (obliquely zygomorphic in Echium and Anchusa arvensis), hypogynous, gamopetalous: S5, P5 (often with ligular outgrowths), A5, G2, but each of the two loculi of the ovary becomes divided by a false partition-wall into two, each of which contains one pendulous anatropous ovule with the micropyle turned upwards; the four loculi arch upwards, so that the ovary becomes 4-lobed, and the style is then, as in the Borageæ, placed at the base (“gynobasic”) between the four projections (Figs. 572, 573). The fruit is a 4-partite schizocarp with four nut-like fruitlets (Fig. 572).—Endosperm is wanting (except in Heliotropium); the radicle is turned upwards.
The INFLORESCENCES are often double unipared scorpioid cymes; the bud of the second bracteole is developed, that of the first suppressed; in some cases both the bracteoles are suppressed (Myosotis, Omphalodes, etc.), but in other instances all the first bracteoles (a) only are suppressed, and the others are then situated in two rows towards the under side of the coiled axis, while the flowers are situated on the upper side. Displacement of the branches or of the floral-leaves sometimes takes place. The flowers are often red at first, and later on become blue or violet; they hardly ever have any smell. The fruit entirely resembles that of the Labiatæ, but the radicle of the latter is turned downwards. The fruitlets present small differences which have systematic importance; they are hollow or flat at the base, attached to a flat or columnar receptacle, etc.
1. Heliotropieæ. This group deviates from the characteristics mentioned above in the undivided ovary and terminal (“apical”) style. In this, as well as in the fact that in some genera (Tournefortia, Ehretia, etc.) the fruit is a drupe, it connects this order with the Cordiaceæ. Heliotropium, Tiaridium, and others have schizocarps.
2. Borageæ, Borage Group. Style gynobasic; fruit a schizocarp.
A. The throat of the corolla is without ligules, or with very small ones.—Pulmonaria (Lung-wort); funnel-shaped corolla; a whorl of hairs in the corolla-throat.—Echium (Viper’s-bugloss) has zygomorphic flowers, the plane of symmetry almost coinciding with that of the very well-developed inflorescence (through the fourth sepal); the corolla is obliquely funnel-shaped, the style is more deeply cleft at the apex than in the others; stamens 2 longer, 2 shorter, and 1 still shorter.—Cerinthe has a tubular corolla with five small teeth and two bilocular fruitlets. The bracts are large and leafy, and, like all the rest of the plant, are almost glabrous.—A few Lithospermum-species have a naked corolla-throat; others have small hairy ligules, which do not close the corolla-throat. The fruitlets are as hard as stone, owing to the presence of carbonate of lime and silica.—Mertensia (Steenhammera); Arnebia; Nonnea (small ligules).
B. The corolla-throat is closed by, or in any case provided with ligules, i.e. scale-like bodies or small protuberances, situated in the throat of the corolla opposite the petals, and which are invaginations or internal spurs of the petals (Fig. 572 D).—The nuts in Cynoglossum (Hound’s-tongue) bear hooked bristles over the entire surface, or, in Echinospermum, only on the edge. The following have smooth nuts:—Symphytum (Comfrey) has a cylindrical, campanulate corolla, and prolonged-triangular, pointed ligules.—Borago (Borage) has a rotate corolla with projecting, emarginate ligules; the stamens have a horn-like appendage, projecting upwards from the back of the filament. The fruitlets are hollow below.—Anchusa (Alkanet, Fig. 572). The corolla is salver-shaped; the ligules small, hairy protuberances. A. (Lycopsis) arvensis has an S-curved corolla-tube.—Myosotis (Forget-me-not, Fig. 573); rotate corolla with small (yellow) protuberances in the throat; scorpioid cyme without floral-leaves; fruitlets flat.—Omphalodes; fruitlets hollow at the back, with a scarious, turned-in, toothed edge.—Asperugo (Mad-wort); the calyx grows after flowering, becoming large, compressed, and deeply bifid.