Fig. 587.—Rubia tinctorum.
In some cases there are apparently 4 leaves in the whorl, and then 2 of these are leaves, and the other two are their interpetiolar stipules. When there are apparently 6 leaves, then the two of these which are opposite each other are leaves, and the other four are stipules; if there are several members in the whorl, then a division of the stipules has taken place. The proof of this theory is founded upon the fact that not more than 2 of the leaves of the whorl ever support buds (which, in addition, are seldom of equal vigour), and also that the whorls do not alternate with each other, which, according to the rules of the position of the leaves, they should do if all the members of a whorl had equal value. If there are, for instance, 4 members in two successive whorls, they stand right above one another, and do not alternate. The development and anatomical relations (the branching of the vascular bundles) also point to the same conclusion.—All the other groups of the order have only 2 small scale-like interpetiolar stipules, or they form at the base of the leaf-stalks an interpetiolar sheath, having often a toothed edge (Fig. 586).—Another characteristic feature in this group is that the calyx is rudimentary, the corolla valvate (Fig. 588), and that each of the two loculi of the ovary has only 1 ovule. The fruit is a schizocarp dividing into 2 fruitlets (Fig. 590). The forms of the fruit, as well as many other characters, as, for example, the epigynous flower, the rudimentary calyx, the two free or almost free styles, present interesting analogous resemblances to the polypetalous order of the Umbelliferæ. This group has its home chiefly in the temperate regions of the northern hemisphere, especially about the Mediterranean; it is the only group which occurs in this country, represented by 4 genera.
Figs. 588–590.—Rubia tinctorum.
Fig. 588.—Diagram.
Fig. 589.—Longitudinal section of flower.
Fig. 590.—Longitudinal section of fruit (3/1).
Galium (Cleavers) is almost destitute of a calyx; it has a small 4-partite, rotate corolla, 4 stamens, and 2 free styles. The fruitlets are nut-like. The inflorescence is a paniculate dichasium passing into helicoid cymes.—Asperula (Woodruff) is distinguished from the above by its salver- or funnel-shaped corolla. 1 style.—Rubia (Madder, Figs. 587–590) has almost the same form of corolla as Galium, but (most frequently) a 5-merous flower, and the fruitlets are “drupes.” Sherardia (Field Madder); the flowers are clustered in closely arranged cymes surrounded by an involucre; the calyx has 6 distinct teeth, while the number of petals and stamens is 4. The corolla is funnel-shaped.—Vaillantia. Crucianella.
The DISTRIBUTION OF SEEDS, in some instances, is promoted by hooked appendages on the fruitlets (e.g. Galium aparine).
The small flowers of the Stellatæ are frequently collected in compact inflorescences, and are therefore rendered more conspicuous; slight protandry is found in some, self-pollination in the species which are less conspicuous. Many species are heterostylous. Myrmecodia, Hydnophytum, and other genera have large tubers (hypocotyledonous stems), whose labyrinthine cavities and passages are inhabited by ants.
About 4,500 species; tropical or sub-tropical except the Stellatæ; especially American. The tropical ones are mostly trees.—Several are OFFICINAL on account of the large amount of alkaloids and glycosides which they contain. The most important are the Cinchonas (Cinchona calisaya, C. succirubra, C. officinalis, C. micrantha, etc.), whose bark contains the well-known febrifuge and tonic, Quinine, Cinchonin, etc.; Quinine is also found in Exostemma, Ladenbergia, and Remijia. The root “Ipecacuanha” (an emetic) from Cephaëlis ipecacuanha (Brazils). Caffeine is officinal. The use of the seeds of the coffee plant (“the beans”) was first known in Europe in 1583.—There are only a few which contain aromatic properties, principally among the Stellatæ (coumarin in Asperula odorata, the Woodruff), in which group colouring materials are also found. The root and root-stalks of Rubia tinctorum, the Madder (S. Eur., Orient., Fig. 587), were formerly largely used for dyeing, but are now superseded by the analine colours. Red dyes are also obtained from the roots of species of Asperula and Galium. Gambier is a splendid colouring material, obtained from Uncaria gambir (S.E. Asia), which is used in dyeing and tanning.—The order does not furnish many ornamental flowers.
Order 2. Caprifoliaceæ. This order agrees with the Rubiaceæ in having opposite leaves and an epigynous flower, most frequently 5-merous with the ordinary tetracyclic diagram, but in some species it is zygomorphic; the corolla has imbricate æstivation, carpels 3–5, most frequently 3 (not 2, which is the most usual number in the Rubiaceæ). The fruit is generally a berry or a drupe, but the most important, and in any case most easily recognisable feature, is the absence of stipules; in exceptional cases, where they are present, they are not interpetiolar, and are most frequently small.—The majority of plants belonging to this order are shrubs or trees. Compound leaves sometimes occur. Stipules only appear in a few species of Lonicera, Sambucus and Viburnum; in the common Elder (Sambucus nigra) they are in some instances glandular and small, but in other cases larger and more leaf-like (upon long, well-developed shoots); in the Dwarf Elder (S. ebulus) they have the normal leaf-like form; in Viburnum opulus they are present as narrow lobes at the base of the petiole; in others they are completely absent. The leaves are frequently penninerved, rarely palminerved. The calyx, as in the Stellatæ and Aggregatæ, is often very insignificant.
1. Lonicereæ, Honeysuckle Group. This has campanulate or tubular corollas which are often zygomorphic; in connection with the length of the corolla the style is long, filamentous, and most frequently has a large, capitate stigma. There are several ovules in the loculi of the ovary, and the fruit is most frequently a berry.
Fig. 591.—Lonicera.
Lonicera (Honeysuckle). Shrubs, sometimes twiners. The corolla in some species is considerably bilabiate (Fig. 591), with 4 lobes in the upper lip, and 1 in the under lip, but in others more regular, tubular, or campanulate. The flowers are either borne in capitate inflorescences, which are compound and formed of closely compressed 3-flowered dichasia (sect. Caprifolium), or in dichasia with 2 flowers (the terminal flower is wanting). The ovaries and fruits coalesce in some (sect. Xylosteum). The opposite leaves in some species unite with each other and form a broad collar encircling the stem (Fig. 591). Above the primary bud 1–2 accessory buds are often found in the leaf-axils.—Diervilla (Weigelia); with a 2-locular, 2-valved capsule.—Symphoricarpus (Snowberry) has an almost regular, funnel-shaped corolla; a peculiar feature is found in the ovary which has 4 loculi, the 2 median having many ovules in 2 rows, all of which are aborted; the 2 lateral ones, on the other hand, each have only 1 ovule which is developed. Different forms of leaves are frequently found on the same branch; they are entire or lobed.
2. Sambuceæ, Elder Group (Fig. 592). This has a rotate, regular corolla, extrorse anthers, a very short and thick (or almost absent) style, with tripartite stigmas, and only 1 pendulous ovule in each of the 3 (-5) loculi of the ovary. The fruit is a “drupe” with 1–3 (-5) stones. The inflorescence is made up of cymes grouped in an umbel-like arrangement.
Sambucus (Elder, Fig. 592) has imparipinnate leaves and a “drupe” with 3 (-5) stones. Between the calyx and the style a disc remains on the apex of the fruit. S. nigra with black fruit; S. racemosa with red fruit; S. ebulus is a perennial herb; the others are woody.—Viburnum (Guelder-rose) has simple leaves (penninerved or palminerved, entire, dentate or lobed), and a “drupe” with only 1 stone, which is compressed, cartilaginous, and parchment-like; 2 of the loculi of the ovary are aborted. (In V. opulus the marginal flowers of the inflorescence are barren, and in that case their corollas are generally specially large; the cultivated Viburnum has only barren flowers, with large corollas.)
Fig. 592.—Sambucus nigra: cor corolla; s calyx.
3. Linnæeæ. Linnæa borealis (the only species) is an extreme form of the order; it has a 2-flowered dichasium, funnel-shaped, slightly bilabiate corollas (2/3); 4 didynamous stamens. Two of the 3 loculi of the ovary have several ovules which are not developed, while the third has only 1 ovule, which developes into a seed. The fruit is a nut, which is enveloped by the two large bracteoles, which are covered by sticky, glandular hairs, and serve as a means of distribution. It is a small undershrub.
[Adoxa, which was formerly classed in this order, appears, according to recent investigations, to be more properly placed among the Saxifraginæ.]
In cases where the flowers are small, as in Sambucus and Viburnum opulus, they are rendered conspicuous by being arranged in closely-packed inflorescences; they are massed together and form large surfaces, and in the last named are still more conspicuous on account of the barren, but large ray-flowers, which are of service in this respect. Honey is secreted in the nectaries at the base of the styles. In the genera with rotate flowers, as Viburnum and other Sambuceæ, the honey lies so exposed and in such a thin layer, that only flies and insects with short probosces can procure it; bees, however, visit these flowers for the sake of the pollen. There is hardly any nectar in the Elder; self-pollination frequently takes place. The flowers of the Caprifoliaceæ, which, with their long corolla-tube are adapted for evening-and night-flying insects with long probosces, open in the evening, and at that time give off their strongest scent.
Distribution. 230 species; especially outside the Tropics in the Northern Hemisphere. In this country they are found especially in hedges and as under-shrubs.—Officinal: the flowers and fresh fruits of the Elder (S. nigra), the fruits (“berries”) being also used in the household. Ornamental shrubs: species of Lonicera, Symphoricarpus, Diervilla, which are chiefly from N. Am., Abelia and Viburnum.
The leaves are opposite and without stipules. The flower (Figs. 593, 595, 598, 599, 600) is epigynous, zygomorphic or asymmetrical, 5-merous with S5, P5, stamens typically 5, but by suppression never more than 4, sometimes less, carpels 3–2. The calyx is more or less insignificant, and almost suppressed in the extreme forms. The ovary has 3–1 loculi, but only one loculus has an ovule, which is pendulous with the micropyle turned upwards (Fig. 594). Fruit a nut. Embryo straight, with the radicle pointing upwards (Fig. 597), without or with endosperm.
The inflorescences are distinct dichasia in Valerianaceæ, but in Dipsacaceæ and Calyceraceæ they are crowded together into capitula.
This family is closely allied to the Rubiales through the Valerianaceæ, which have almost the same structure as many of the Caprifoliaceæ. It attains the highest development in the Dipsacaceæ, which are composite plants, but differs from Compositæ in the position of the ovule, etc.
Order 1. Valerianaceæ. Herbaceous plants or under-shrubs with opposite leaves, often pinnate; stipules absent. The flowers are borne in dichasia and in scorpioid cymose inflorescences and are entirely without any plane of symmetry (Fig. 593). The calyx and corolla are 5-merous, but the calyx is frequently very insignificant and ultimately a pappus, as in Compositæ; the corolla is frequently saccate or produced into a spur at the base. Most frequently, only 3 (4–1) of the 5 stamens are developed; these are free. Carpels 3, which form an inferior ovary, often with 3 loculi, but only 1 of the loculi contains 1 pendulous, anatropous ovule (Figs. 593, 594 A), the other loculi are empty and shrink up more or less completely. (Compare Fig. 593 A, B). Style 1, stigma tripartite. Endosperm absent; embryo straight, with the radicle directed upwards.
The inflorescences are dichasia, or unipared scorpioid cymes with the branches developed in the axil of the second bracteole. Both the bracteoles are generally present and frequently form 4 very regular, longitudinal rows on the branches of the inflorescence.—5 stamens do not occur (except perhaps in Patrinia). The suppression of stamens and carpels takes place most readily on the anterior side of the flower and that turned towards the first bracteole (a) (Fig. 593), whose branch is suppressed in the dichasium; after this the posterior median stamen is next suppressed.
By the vegetative characters as well as by the inflorescence and the flower, the order is allied to the Caprifoliaceæ and especially to the Sambuceæ.
Fig. 593.—A Diagram of Valeriana officinalis. B Diagram of Centranthus.
In the least modified (oldest) forms, Patrinia and Nardostachys, there is an almost regular flower, a 5-merous calyx, 4 stamens, and 3 loculi in the ovary, 2 of which however are barren. The stamens in Valerianella are reduced to 3, in Fedia to 2 (posterior), and the calyx is less distinctly 5-dentate; the 2 empty loculi in the ovary are still visible. Fedia has a small spur at the base of the corolla. Valeriana has a very reduced, hair-like calyx (pappus), an unsymmetrical, salver-shaped corolla with a sac-like, nectariferous spur at the base, 3 stamens and only 1 loculus in the ovary (Figs. 594, 593). Centranthus (Fig. 593) is still further reduced. The corolla has a spur and only 1 stamen; unipared scorpioid cymes with 4 rows of bracteoles. In the last two genera there is a peculiar wall in the corolla-tube, which divides it longitudinally into two compartments (indicated by a dotted line in Fig. 593), one of which encloses the style. This wall is low in Valeriana, but in Centranthus it reaches as far as the throat.—The rays of the pappus are pinnately branched and rolled up before the ripening of the fruit. 12–20 in number (Fig. 594 A, B).
Val. officinalis and others are protandrous: in the first period the stamens project from the centre of the flower (Fig. 595 a), the stigmas in the second (b) when the stamens have become bent backwards. (V. dioica is diœcious with large ♂-and small ♀-flowers).—275 species; especially from the temperate and colder parts of the northern hemisphere of the Old World, Western North America and the Andes.—Bitter properties are characteristic, such for instance as the volatile acid and volatile oil of Valeriana; these occur especially in the rhizomes. Officinal; the rhizomes of V. officinalis.—The true Indian “Nardus,” an important medicine and perfume in India, is extracted from Nardostachys (Himalaya). A variety of Valerianella olitoria is sometimes used as salad.
Fig. 594.—Valeriana: A ovary (longitudinal section); B ripe fruit.
Fig. 595.—Valeriana: a flower in the ♂ stage; b in the ♀.
Fig. 596.—Centranthus ruber. Flower, its lowermost portion (the ovary and spur) in longitudinal section. (Mag.)
Fig. 597.—Scabiosa atropurpurea. Fruit in longitudinal section. Inside the “epicalyx” may be seen the fruit drawn out into a beak, with straight embryo and radicle directed upwards.
Order 2. Dipsacaceæ (Teasels). Herbs with opposite leaves without stipules. The flowers are situated in compact capitula each with an involucre. A characteristic feature of the order is that each flower of the capitulum has a gamophyllous “epicalyx” (Figs. 597, 599, 600), which envelopes the inferior ovary. The flowers (Figs. 599, 600) are ☿, 5-merous (S5, P5, stamens typically 5, G2), but the calyx often expands at the edge into a membrane with 5, or an indefinite number of bristles or teeth (pappus, Figs. 597, 600), and the zygomorphic, funnel-shaped corolla is sometimes 5-lobed and bilabiate (2/3), but most frequently 4-partite (Fig. 599), the two lobes of the upper lip coalescing into one lobe, as in certain Labiatæ, Veronica and Plantago; the æstivation is imbricate.
Figs. 598–600.—Dipsacus fullonum.
Fig. 598.—Inflorescence (the flowers in a zone below the apex commence to flower first).
Fig. 599.—Flower (4/1).
Fig. 600.—The same in longitudinal section.
The stamens are never more than 4, the posterior one remaining undeveloped; they usually have free anthers which generally project considerably (Fig. 599). The ovary is unilocular with 1 pendulous ovule and bears 1 undivided style; fruit a nut with 1 seed, containing endosperm and with the radicle turned upwards (Fig. 597).
The flowers do not always open in centripetal order, a fact which may be observed especially in the Dipsacaceæ, in which a zone of flowers round the centre of the capitulum opens first, and the flowering then proceeds both upwards and downwards (Fig. 598). This has probably some connection with the fact that the capitulum has arisen from the coalescence of several dichasial inflorescences. In species of Scabiosa the flowers open simultaneously at the circumference, or in a zone at the centre.—The morphological explanation of the “epicalyx” is not quite certain; in all probability it is formed from two united bracteoles, for an “epicalyx” is distinctly formed in this way in one of the Valerianaceæ, Phyllactis.—The ray-flowers are larger and more irregular, labiate or ligulate, than the disc-flowers, yet not in so high a degree as in the Compositæ.
A. A scarious bract to each flower. Scabiosa has a 5-lobed corolla; the “epicalyx” has a dry, scarious, often finally large collar, and the true calyx is formed of long bristles (generally 5) (Fig. 597). Succisa pratensis (Devil’s-bit) has a 4-lobed corolla, the collar of the “epicalyx” is herbaceous; the calyx as in the preceding.—Pterocephalus.—Dipsacus (Teasel); large, spiny and stiff-haired herbs with capitula, or short, thick spikes on which both the involucral-leaves and bracts project considerably, and are stiff and spinose (Fig. 598). The “epicalyx” has short teeth, or is almost entire. The leaves of the stem unite together in pairs, so that shallow cups are formed round the stems in which rain-water may collect.—Cephalaria.—Morina: the flowers are falsely verticillate as in the Labiatæ; the calyx has 2 laterally-placed, entire, or emarginate lobes; 2 stamens, or 2 large and 2 small ones.
B. Bristles, but no true bract to each flower. Knautia; the corolla is 4-partite, the calyx cup-like, with many bristles or teeth on the edge.
Pollination is in many species effected by insects. The honey is secreted by a ring round the base of the style. The flowers in our native species are considerably protandrous. Gynodiœcious flowers also occur.—150 species; especially in the Mediterranean and the Orient; the order is not represented in the South Sea Islands, Australia and America.—The heads of the true Teasel (Dips. fullonum) are used for carding wool, on account of the elastic bracts, which are hooked at the point. The order has bitter properties; tanin, etc.; but no species are used in medicine or the household.—Scabiosa atropurpurea, etc., are used as ornamental plants.
Order 3. Calyceraceæ. This order resembles the Compositæ in the valvate æstivation of the corolla and the more or less united stamens, and the Dipsacaceæ in the undivided style, pendulous ovule and endosperm. The calyx is frequently composed of 5 distinct scales. An “epicalyx” is wanting.—20 species; America.
The flower is epigynous, perfect, with 5 sepals, 5 petals, and 5 stamens in regular alternation, and 3 (2–5) carpels. The sepals in all cases are distinct, but narrow and pointed, so that the æstivation is open. The corolla is gamopetalous with (as in the Compositæ) valvate, or slightly infolded-valvate æstivation. The stamens are nearly always situated on the torus without being united to the corolla (Figs. 601, 604). The anthers adhere or unite and form a tube with introrse anthers from which the pollen is swept out by the projecting, brush-like hairs on the style (as in the Compositæ). The ovary is 3-(2–5) locular, many ovules in each loculus. The fruit is generally a many-seeded capsule (or berry). Embryo in the centre of a fleshy endosperm.—The majority are herbs with scattered leaves, without stipules. The presence of latex and inulin, together with the tubular formation of the anthers, the pollination, etc., indicate a relationship with the Compositæ.
The Cucurbitaceæ are by some authorities placed in this family as being most closely related to the Campanulaceæ. Although the corolla is most frequently gamopetalous, and other similarities to the Campanulaceæ are present, yet on account of the structure of the ovule, and for other reasons, the Cucurbitaceæ are here placed in the Choripetalæ. The Campanulinæ without doubt proceed upwards to the Compositæ, with which, in addition to the occurrence of inulin and laticiferous vessels (Cichorieæ), there are many corresponding features both in the structural and biological relations (epigyny, valvate æstivation of the corolla, tendency of the anthers to adhere or unite, protandry with a stylar-brush, etc.) The inflorescence of Jasione is almost identical with that of the Compositæ.
Order 1. Campanulaceæ (Campanulas). The flowers are regular and in some only semi-epigynous, 5-merous, except in the gynœceum which is 3-merous (the unpaired, median carpel being generally posterior), more rarely 2–5-merous, and has a corresponding number of stigmas and loculi in the ovary; the placentation is axile with a large number of ovules. The median sepal is posterior. The stamens frequently have broad, free bases (Fig. 601 H) which cover the nectariferous upper surface of the ovary; the anthers only fit loosely together, and become separated as soon, as the pollen is shed (Fig. 601 G), 1 long style, which is studded by sweeping-hairs (stylar-brush), which ultimately become invaginated; the stigmas do not unfold until the stamens have shed the pollen (Fig. 601 E, G). Fruit a capsule.—Herbs, more rarely under-shrubs or shrubs, with latex and scattered, undivided leaves without stipules. The inflorescence is most frequently a raceme or spike with terminal flower.
A. Capsule opening at the side by pores and small valves: Campanula (Canterbury-bell); the corolla is bell-shaped, rarely almost rotate; capsule obconical. The pores of the capsule are found near the top of the fruit when it is erect, and near the base when it is pendulous, so that the seeds are not liberated unless the capsule is forcibly shaken, and they are thus ejected to a considerable distance.—Phyteuma (Rampion) has free petals, which for a long time adhere at the apex and form a tube round the stamens (Fig. 601); inflorescence compact, spike-like or capitate, in the latter case resembling that of the Compositæ, and frequently with an involucre similar to the one possessed by this order. Specularia (rotate corolla, prismatic capsule), Michauxia (flower 8-merous).—Symphyandra has syngenesious anthers.
B. Capsule with valves at the apex, loculicidal dehiscence: Jasione; the petals are almost free. The anthers are united at the base (syngenesious). The flowers are situated in capitate umbels with involucres.—Wahlenbergia; Platycodon.
Fig. 601.—Phyteuma spicatum. Flowers and parts of flowers in various stages of development.
C. Berry: Canarina; flower, 6-merous; leaves opposite.
Protandry is general (Fig. 601). 510 species; principally in temperate countries. Several genera furnish ornamental plants, but are of little use for other purposes. The roots of some Campanula-and Phyteuma-species are large and may serve as pot-herbs (C. rapunculus, P. spicatum).
Order 2. Cyphiaceæ. In this order the corolla is zygomorphic and the stamens free, hence it is intermediate between orders 1 and 3.—About 24 species; Africa.
Order 3. Lobeliaceæ (Lobelias). This order may briefly be described as Campanulaceæ with zygomorphic flowers and anthers united into a tube, in most cases slightly bent; generally 2 carpels and an inverted position of the flower, i.e. the median sepal is turned anteriorly (Fig. 602) (a position which is found to occur within the Campanulaceæ). A twisting of the peduncle takes place even before flowering (as in the Orchids) so that the ordinary position of the 5-merous Dicotyledons appears to be restored. The zygomorphy of the flower is especially present in the corolla, which has a bipartite under-lip and a tripartite upper-lip, and is, in Lobelia, anteriorly (apparently posteriorly) deeply cleft (Fig. 602). There is 1 style, but the stigma is capitate and bilobed and surrounded at its base by a whorl of hairs, which assists in pollination (as a stylar-brush) in the same manner as the sweeping-hairs in the Campanulaceæ and Compositæ. There is no terminal flower in the spicate, or racemose inflorescences.—Lobelia has a capsule, several others have berries. Isotoma (regular flower); Heterotoma has a spur; Siphocampylos; Lysipoma (pyxidium); Clintonia (1–locular fruit). Metzleria (all the petals are free).
Fig. 602.—Diagram of Lobelia fulgens.
Figs. 603, 604.—Lobelia syphilitica.
Fig. 603. Flower (2/1).
Fig. 604.—Longitudinal section of the same.
Entomophilous and protandrous. About 500 species, especially in the Tropics; in this country, L. dortmanna (margin of lakes).—Several are cultivated in gardens and conservatories as ornamental plants (Lobelia bicolor, erinus, fulgens, etc., Siphocampylos, Centropogon). The latex of several species of Tupa is poisonous; caoutchouc is also obtained from them. Officinal: “herba Lobeliæ” (the alkaloid lobeline) from the poisonous L. inflata (N. Am.).
Order 4. Goodeniaceæ. Chiefly Australian (200 species), closely related to Orders 3 and 5, but without latex. The style is provided with a “collecting-cup” which receives the pollen before the flower opens; it has a small, hairy aperture through which the pollen is forced out by the stigmas, and through which they emerge when the pollen is shed; it is sensitive and exhibits movements when touched.—Herbs, under-shrubs, less frequently shrubs. Goodenia, Leschenaultia, Scævola.
Order 5. Stylidiaceæ (or Candolleaceæ); 100 species, the majority Australian; zygomorpbic flowers, but with the ordinary position. The anterior petal is very small. The chief characteristic feature is the presence of only 2 stamens (with extrorse anthers) which are united with the style and form a stylar-column; this is bent like a knee and sensitive at the bend to such a degree that when touched it jerks violently across the flower to the opposite side and then loses its sensitiveness.—Herbs, less frequently under-shrubs. Stylidium (Candollea).
The flowers, which are borne in “capitula” (Figs. 605, 610), are epigynous (Fig. 605 C, D), 5-merous in the calyx, corolla and andrœcium, the corolla is valvate in æstivation, with 2 carpels (S5, P5, A5, G2). The anthers are united into a tube (syngenesious) (except Ambrosieæ) which surrounds the bifid style. There is never more than 1 loculus in the ovary, with 1 erect, anatropous ovule. The fruit is a 1–seeded nut (cypsela), with thin pericarp, the calyx generally persists as a tuft of hairs (pappus) (Fig. 606) on the summit of the fruit. Embryo without endosperm; the radicle directed downwards.
Only 1 Order: Compositæ.
With respect to the inflorescence and the development of the individual flowers, there is a very close resemblance to the Dipsacaceæ, which stand on the same plane of progression as the Compositæ. But while the latter are allied to Campanulinæ as the last stage in the process of evolution, the Dipsacaceæ form the final stage of the Rubiales-Dipsacales.
Order Compositæ. (For the principal characteristics compare those of the family.) The Compositæ are chiefly herbs, but trees and shrubs also occur in tropical countries. The leaves may be scattered or opposite, but have no stipules. The outer leaves of the involucre as a rule are barren, especially when numerous and imbricate, while the innermost ones support the ray-flowers of the capitulum; in a few instances all are fertile (e.g. Tragopogon, Tagetes). The CAPITULA are many-flowered, with the exception, e.g. of Echinops, which has 1-flowered capitula (see page 570). The capitula are again arranged in inflorescences, most frequently corymbose with centrifugal order of development. The form of the receptacle is an important character for the division of the genera (flat, convex, conical), and also the presence of scales; these may be one scale (bract) for each flower (Fig. 610 br), or a large number of bristles, which do not each correspond to a leaf, or the receptacle may be entirely without covering (naked). The flowers open in acropetal order in each capitulum. All the flowers in a capitulum may be of the same sex, and their form and colour are in that case the same, or the sexes may be different, in which case the form and colour are also most frequently different: the ray-flowers have projecting labiate or ligulate corollas, while the disc-flowers have tubular corollas. As a rule in the latter case the ♀ flowers are at the circumference, and the ☿ in the centre, less frequently ♀-flowers at the edge and ♂-flowers in the centre. The ray-flowers in some genera are neuter (e.g. Centaurea). Some are diœcious.
Fig. 605.—Calendula arvensis: A capitulum; B capitulum in longitudinal section; C ♀-flower; D ☿-flower; E the stamens; F capitulum with ripe fruits; G ripe fruit.
There is no trace of an epicalyx (in contrast to the Dipsacaceæ, which they generally so resemble). The formation of the CALYX is very varied. The calyx always consists of a very small cushion-like structure, most frequently developed later than the corolla; the 5 corners, which correspond to the 5 sepals, in a few instances are raised as 5 large, flat, membranous bodies, e.g. in species of Xeranthemum, Catananche, Sphenogyne, etc.; in other instances each of these bears a shorter or longer bristle on its apex, followed by others in rather uncertain numbers and with but slight indications of order, on the edge and on the outer side of the calyx between the 5 points; in other instances, again, the calyx is covered with bristles and hairs without any indication of order or definite number (Fig. 606 a, b); finally instances occur in which the edge is raised as a membranous collar, irregularly toothed and notched, or divided into small scales. There are naturally differences in the means of distribution corresponding to the differences in structure of the calyx. The fruits a and b represented in Fig. 606 are distributed by the wind, those like c, on the other hand, by attaching themselves to animals and human beings. The rays of the pappus are termed rough when special cells project a little beyond the surface, but if these grow out, and are hair-like, the pappus is said to be feathery. In some genera the pappus is raised on a long stalk, which is developed from the upper part of the fruit, and termed a beak (Fig. 606 a). The pappus does not attain its full development till the ripening of the fruit, i.e. until it is about to be of use.
Fig. 606.—a Fruit of Taraxacum; b of Senecio; c of Bidens.
The COROLLA has various forms: (a) tubular (Fig. 605 D), with a shorter or longer tube, not always of the same bore throughout and especially slightly widened at the top to form a bell-shaped opening, with 5 regular teeth: (b) labiate after 2/3, i.e. with 2 petals in the upper and 3 in the under lip: (c) ligulate, i.e. the corolla is split for a considerable distance on the posterior side (as in the Labiate genus Teucrium) and prolonged into a long, strap-like portion (Fig. 609 A), which projects upwards. A distinction must, however, be drawn between the true and false ligulate corolla. In the first case the corolla has 5 teeth at the apex (Fig. 609 A) and is made up of all the petals of the corolla united together; this is the usual condition in the Ligulate-flowered. In the latter case (Fig. 605 C) the tongue has only 3 teeth (or is more irregularly 2–3-dentate), and is only formed of 3 petals; the corolla is then truly bilabiate, the tongue is the large under lip, and the upper lip is very slightly developed, or even at an early stage quite suppressed. This false “ligulate” corolla is found among the ray-flowers; sometimes the upper lip is seen quite plainly, e.g. in Tagetes, especially in the double capitula. The VENATION of the corolla is peculiar; there are always commisural veins which branch dichotomously at the angles between the teeth of the corolla, and send a branch into the edge of the two nearest teeth. The midrib is frequently absent, but may be present, and then it has sometimes no connection with the other veins of the corolla.
Fig. 607.—Centaurea cyanus: A the anther-tube (st) with the crescentic curved filament before irritation; g the style; k the base of the corolla; B the same after irritation, the anthers are drawn further down.
The STAMENS are attached to the corolla, and have free filaments (Silybum has united filaments), but the anthers, which at first are free, adhere together and form a tube (Fig. 605 E: only Ambrosieæ have free anthers). The connective is generally prolonged, and protrudes above the anthers as a thin, brown membrane of various forms (Fig. 605 E); appendages of various forms may also be found at the base of the anthers. The anthers open introrsely, and the pollen must be carried out at the top of the tube by upward growth of the style, and by means of the “stylar-brush” (Figs. 607, 608, 609); the filaments are sometimes sensitive (e.g. in the Corn-flower, Fig. 607), and shorten on being touched, so that the anther-tube is pulled downwards, and the pollen swept out at the top (Figs. 607, 608 A, B).