Part 74

POLLINATION. Insect-pollination in the majority; cross-pollination is promoted in some by heterostyly (Fig. 548).--300 species; especially in northern temperate zones; the majority on mountains (Soldanella, Androsace, etc.); almost absent in the Tropics. A large number are ORNAMENTAL PLANTS, e.g. Primula auricula (from the Alps), P. sinensis (China), P. elatior (Oxslip, a native) and grandiflora, etc. Cyclamen europæum (Alpine Violet); the tubers are poisonous.

Order 2. =Myrsinaceæ.= Trees or shrubs; evergreen, tropical Primulaceæ with fleshy fruits and few seeds, embedded in the placenta. The leaves are nearly always dotted with yellow glands (schizogenous resin-receptacles).--550 species; especially Am.--ORNAMENTAL PLANTS: Ardisia crenulata (W. Ind.); other genera: Clavija, Maesa, Theophrasta (barren sepal-stamens), Myrsine, Jacquinia (barren sepal-stamens), etc.--Ægiceras, allied to this order, comprises arborescent plants, often growing with Rhizophora in tropical forests, along the shore. The embryo germinates while still in the fruit.

Order 3. =Plumbaginaceæ.= This order has a position of the stamens similar to that in Primulaceæ (S5, P5, A0 + 5, G5), but it differs from these in the flower, which has generally a membranous, dry, thin, coloured, folded, almost entire calyx and an almost entirely polypetalous corolla, which, as a rule, has twisted æstivation and is only united with the stamens at its base; but more especially it differs in the ovary, which bears 5 free or almost free styles and only 1 basal ovule with a long, twisted funicle (the placenta of the Primulaceæ is here so much reduced that it bears only 1 ovule). The fruit is a nut or capsule. The radicle is turned outwards. Endosperm mealy.--To this order belong herbs or under-shrubs, which are especially natives of the sea-coast and of salt-steppes; they also resemble the Primulaceæ in the scattered, undivided, entire leaves (without stipules), often in rosettes, and the inflorescence borne on a long stalk. In opposition to the Primulaceæ, the bracteoles are typically present, and hence the branching is generally cymose (scorpioid).

Armeria (Thrift) has a round capitulum, composed of closely-packed dichasia, surrounded at its base by an involucre with peculiar prolongations, directed downwards, and united into a sheath protecting the intercalary zone of growth. The pericarp is finally ruptured at the base, and drops off like a hood.--In Statice (Sea-lavender), the unipared scorpioid cymes are prolonged and collected into panicle-like inflorescences.--~Plumbago is the genus which approaches nearest to the Primulaceæ, and differs most from the characters given above. It has capitate or spike-like inflorescences, a salver-shaped corolla, and the stamens are not attached to the corolla. The style is only divided at the extremity; the calyx is not membranous, but is covered with sticky, glandular hairs.~

250 species; chiefly in the Mediterranean and about the Caspian Sea, on salt-steppes and beaches. Some are Tropical; a few are ornamental plants.

B. Tetracyclicæ.

a. Tetracyclicæ with hypogynous flowers.

Family 29. =Tubifloræ.=

The flower is regular, ☿, and hypogynous. The gamopetalous type is present in this family with great uniformity, without suppression or splitting; S5, P5, A5, G2 (3–5). The stamens are all fertile, alternating with the lobes of the corolla. Gynœceum with 2, more seldom 3–5 syncarpous carpels. Style nearly always simple; 2 dorsal stigmas. In each carpel 2–∞ ovules. At the base of the ovary is found a yellowish ring-like nectary (Fig. 552 C), sometimes 5-sinuate or 5-partite.--The leaves are nearly always scattered; stipules are absent.--~The Solanaceæ, which formerly were classed here, are so closely allied to the Personatæ, that it would be unnatural not to place them first in this family; and the Boraginaceæ (which were also placed in the Tubifloræ) appear to be best united, with the Labiatæ and others, into one family Nuculiferæ.~

Order 1. =Polemoniaceæ.= The flowers are regular; S5, P5, A5, G3. The calyx and corolla have united leaves, the petals twisted to the right in æstivation (all the left edges being covered). The ovary is 3-locular with 2–∞ ovules in each loculus; the style is trifid at the apex; the fruit is a 3-valved capsule. Embryo straight; endosperm fleshy. The inflorescences are dichasia passing over into unipared helicoid cymes (the shoot of the lower bracteole being the more strongly developed).--Herbs without latex. 150 species; especially Western N. Am.--Phlox (salver-shaped corolla; entire, opposite leaves), Polemonium (campanulate or almost rotate corolla; scattered, pinnate leaves), Leptosiphon, Gilia, Collomia, Cobæa (climbing, like the Vetches, by tendrils at the ends of the leaves), etc. They are frequently ornamental plants.

Order 2. =Hydrophyllaceæ.= This order approaches very closely to the Boraginaceæ. Herbs with pinnate or palmate leaves; S5, P5, A5, G2. The lobes of the corolla are imbricate in æstivation. Generally 2 median carpels. The ovary is most frequently unilocular, and the seeds are situated on 2 parietal placentæ; capsule 2-valved; embryo straight; endosperm fleshy. In the corolla-tube, opposite the corolla-lobes, there are frequently appendages of various forms, which resemble those of Cuscuta. The inflorescences correspond exactly with those of the Boraginaceæ, being unipared scorpioid cymes, which, prior to opening, are tightly rolled up.--130 species, especially in N. Am. (California, etc.). Many annual species of Phacelia, Nemophila, Whitlavia, Eutoca, Cosmanthus, etc., are cultivated in gardens as ornamental plants. Hydrolea (has a bilocular ovary, and two free styles).

Order 3. =Convolvulaceæ= (=Bindweeds=). The flower is regular, hypogynous, with 5 almost free sepals (quincuncial æstivation), P5, A5, G2 (rarely 3–5). The corolla is very characteristic; it is (with various forms) almost entire, or slightly 5-lobed, and folded longitudinally in the bud in such a way that 5 projecting, flat portions, tapering towards the top and frequently differing in colour and hairiness from the rest, are visible externally and applied close together, while the remainder of the corolla is folded inwards (Fig. 552 A); and hence the whole corolla is strongly twisted to the right in the bud. The gynœceum most frequently has a bilocular ovary; in each loculus there are only 2 (erect) anatropous ovules on the placenta, which is not especially thickened (Fig. 552 D, E); each loculus is sometimes divided into two by a false septum (a relationship with the Boraginaceæ, etc.); style simple with most frequently a bilobed stigma, or a bipartite style. The fruit is nearly spherical, most frequently a capsule. The seeds are erect, and have a large hilum at the base. The embryo is curved, with leaf-like, thin, bilobed, most frequently folded cotyledons; endosperm absent or mucilaginous.

=1.= CONVOLVULEÆ, BINDWEED GROUP. The majority are twining (to the left) herbs, with latex. The leaves are scattered, without stipules, often long stalked, and nearly always with cordate base; some are palmately lobed. The flowers are most frequently solitary in the leaf-axils, large, quickly withering.--Convolvulus (Fig. 552), Calystegia (unilocular ovary, 2 large bracteoles), Ipomœa, Batatas, Evolvulus (with a doubly bifid style), Calonyction, Pharbitis, etc.

=2.= DICHONDREÆ. This group is a more primitive form, not twining, and without latex. It has 2 free carpels with basal style (as in Boraginaceæ) and valvate corolla.

=3.= CUSCUTEÆ, DODDER GROUP (Fig. 553). Parasites, with round, filamentous stems, bearing only scale-like leaves and almost destitute of chlorophyll (they are reddish or yellowish); they are parasitic upon other plants, around which they twine, first with narrow, compact coils from which haustoria (Fig. 553 A) are developed which enter the host-plant, and then with wider coils by which they raise themselves to other portions of their host or try to reach other plants. On germination a very temporary primary root is developed, which bears root-hairs as far as the tip (rootcap is wanting); it only serves as a kind of reservoir for water, and perishes very soon after the seedling has fastened on to a host. The embryo is filamentous and rolled up spirally (Fig. 553 C), and is sometimes destitute of cotyledons. The flowers are crowded into capitulate inflorescences, complicated by accessory shoots (Fig. 553 A); they have S5, P5 (imbricate æstivation), A5 (and beneath the stamens 5 scales on the corolla-tube), G2. Fruit a capsule opening by a lid.--Cuscuta europœa, C. epilinum (Flax-Dodder), C. epithymum (Lesser-Dodder), C. trifolii (Clover-Dodder), etc., are parasitic on different hosts, or parasitic each on its own particular host.

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.

Family 30. =Personatæ.=

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.

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.

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 (f^1 and f^2), 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 (f^1) of the two leaves on each shoot is barren, and is therefore not displaced; but the upper one (the second bracteole, f^2) is displaced as in the first instance, and consequently it assumes a position near the first leaf (the shaded leaf f^2 of shoot I being placed near the white leaf f^1 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.

=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).

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.