A Handbook of Systematic Botany, by Dr. E Warming

The STYLE divides at the apex into two branches (Figs. 609, 610), both of which generally bear on the inner surface two lines of stigmatic papillæ (Fig. 610 B, C) and being in shape, etc., very varied, are therefore employed as systematic characters.—The most important types are: A. The style is uniformly cylindrical; its branches are semi-cylindrical, long, and with long hairs, and finally bend backwards; the stylar branches bear slightly projecting stigmatic papillæ on the inner side. This form is characteristic of the Cichorieæ (Fig. 609 A B). B. The style is uniformly cylindrical; the branches are long, cylindrical or club-like, short, not rolled back, with fine hairs externally; the stigmatic lines do not reach beyond the centre, and do not meet together. Characteristic of Eupatorium, Petasites, Tussilago. C. The style is thickened beneath the stigmatic branches in the form of a knob, or very hairy (Fig. 609 C); the stigmatic lines reach as far as the apex of the branches and then converge; sometimes the stigmatic branches are united as far as the apex. Characteristic of the Cynareæ. D. The stylar branches are lanceolate, or linear, pointed; externally flat and thickly covered with hairs in the upper portion; the stigmatic lines cease where the hairs commence externally. Characteristic of Aster, Bellis, Inula, Dahlia, etc. E. The stylar branches are linear, with long, brush-like hairs at the apex, where they are either abruptly cut off or prolonged into a very hairy, conical appendage; the stigmatic lines are broad, reach as far as the brush-like hairs, and do not meet together (Fig. 610). Characteristic of Senecio, Helianthus, Xanthium, Gnaphalium, Artemisia, Anthemis, and others related to these.

The thin-walled cypsela (Fig. 606), with seeds fitting closely to the pericarp, has many different forms (smooth, ribbed, spined, etc.); its point of attachment generally lies at the lowest end but sometimes it is drawn obliquely up the side (Centaurea, etc.). The calyx, persistent on the apex of the fruit, has been described above. Some genera have two or three different forms of fruits in each capitulum.—The embryo is straight, with the radicle turned downwards, and without endosperm, but is rich in oil.

The variously flowered capitula, whose normal tubular disc-flowers have been changed to ligulate flowers, may be termed “double flowers.”

The relationship of the Compositæ to the Campanulinæ has been described above (page 561). The alliance with the Dipsacaceæ is more apparent than real. Similar capitate inflorescences also occur as the final stage in other lines of descent, as in Eryngium among the Umbelliferæ.

1. Cynareæ, Thistle Group. Flowers all ☿, regular, with tubular corollas. The receptacle is covered with numerous bristles, which surround the flowers without any definite order, or the edges of the grooves in which these are placed have a well-marked fringe. The involucral leaves are numerous, imbricate, and are either prolonged into a thorn or terminate with a membranous edge. The style has been described on page 568 (Fig. 609 C). Nearly all have a hairy or feathery pappus. The filaments are sensitive.

Carduus (Thistle); capitula ovoid; involucral leaves compact, imbricate, with thorny points; the pappus-rays are hair-like and united at the base by a ring (i.e. the calyx), and fall off together.—Cirsium (Fig. 608) has a feathery pappus, in other respects it is like Carduus. C. arvense reproduces and passes the winter by means of suckers.—Cynara (Artichoke) has a feathery pappus and large, solitary capitulum, with broad involucral leaves; these have a fleshy base like the receptacle (edible).—Silylum has united filaments. S. marianum (Milk-thistle), has leaves with numerous white spots. Onopordon (Cotton-thistle). Cnicus (C. benedictus) has a large, many-spined thorn on the involucral leaves; pappus trimorphic.—Lappa (Burdock) is easily recognized by the hooked involucral leaves, which assist in the distribution of the fruit; in this respect it differs from the other inflorescences, and also in the fact that the pappus is short, and quickly falls off, without serving as a means of distribution.—Carlina; the external involucral leaves are leafy, thorny, with branched or unbranched spines standing straight out or bent backwards; the internal ones are dry, and prolonged as dry, coloured, radiating scales. The well-developed bristles on the receptacle and edge of the calyx are deeply cleft and lobed.—Centaurea (Knap-weed, Fig. 607). The ray-flowers are neuter, and generally larger than the disc-flowers; the involucral leaves are regularly imbricate, but are frequently provided at the apex with a dry, chaffy, often lobed, fringed appendage. The attachment of the fruit is lateral. Serratula (Saw-wort).—Carthamus, the outer and inner involucral leaves differ very much.—Echinops (Globe-thistle) is characterised by having “compound capitula,” i.e. there is only one flower in each capitulum, but many such capitula are collected into a spherical head, which at the base may also have a few involucral leaves. The individual capitula have narrow, linear involucral leaves. (There are altogether about 150 species of Compositæ with 1-flowered capitula, all from warm countries.)—Xeranthemum, Staehelina, Jurinea, Saussurea, etc.

2. Mutisieæ, Labiate-flowered Group. Tropical (S. American) forms whose zygomorphic flowers have a bilabiate corolla (2/3). The involucre is nearly the same as in the Thistles.

3. Cichorieæ, Chicory Group (or Ligulifloræ). The flowers are all ☿ and have a ligulate, 5-dentate corolla. The stylar branches are thin and prolonged (Fig. 609 B). Laticiferous vessels occur in the majority (in this feature they resemble the Lobeliaceæ and Campanulaceæ).

A. The pappus is wanting, or it is scale-like, but not long and hairy.—Cichorium (Chicory); capitula with blue flowers, borne singly or a few together in the leaf-axil; there are two whorls of involucral leaves, an outer one of short and radiating, an inner of more numerous, longer and erect leaves; pappus, scale-like.—Lapsana (Nipplewort). The few involucral leaves are nearly of the same size, and persist forming a sort of capsule round the fruits, which are entirely without a pappus. There are only a few flowers in the small capitula.—Arnoseris (Swine’s-succory), Catananche, etc.

B. The pappus is long and hairy (not branched), generally fine and snowy-white. There are no scales on the receptacle. The two genera first considered have beaked fruits.—Taraxacum (Dandelion) (Fig. 606 a); the capitula are many-flowered, and borne singly on the top of a leafless, hollow stalk.—Lactuca (Lettuce) has many small, few-flowered capitula borne in panicles.—Crepis (Hawksbeard).—Hieracium (Hawk-weed) has many imbricate involucral leaves, and a stiff, brittle, brownish pappus.—Sonchus (Sow-thistle); the capitula, when a little old, have a broad base, and are abstricted above in the form of a jug; involucral leaves imbricate; the fruit is compressed, without a beak, ridged. The soft, white pappus falls off collectively.

C. The pappus is feathery and branched; no scales on the receptacle.—Tragopogon (Goat’s-beard) generally has 8 involucral leaves in one whorl. The fruit has a long beak; the rays of the pappus are interwoven in the form of an umbrella.—Scorzonera has fruits like the preceding, but almost without any beak; involucral leaves many, imbricate.—Leontodon (Hawkbit) has a slightly feathery pappus, rays not interwoven; beak absent.—Picris.

D. Long, chaff-like, deciduous scales on the receptacle; pappus feathery.—Hypochœris (Cat’s-ear).

4. Eupatorieæ, Hemp-agrimony Group. All the flowers are most frequently ☿; corollas tubular and regular; the involucral leaves are not stiff and spiny; the receptacle is not covered with stiff bristles. The stylar branches are long, club-like, or gradually tapering. There is no swelling below the stigma.

Eupatorium (Hemp-agrimony); all the flowers are ☿.—Petasites (Butterbur); ray-flowers ♀, disc-flowers ☿ or ♂; sometimes diœcious. Capitula in racemes or panicles. The leaves develop after the flowering.—Tussilago (T. farfara, Colt’s-foot) has a solitary capitulum borne on a scaly, scape-like stem; the ray-flowers are ♀ with ligulate corollas, disc-flowers ♂. The leaves unfold after the flowering. Ageratum, Mikania, Vernonia.

5. Astereæ, Aster Group (or Radiatæ, Ray-flowered). The flowers are of two forms and different sexes; the ray-flowers are ♀ (sometimes neuter), most frequently with irregular, falsely ligulate, radiating corollas; the disc-flowers are ☿, regular, with tubular corollas (Fig. 610). Sometimes only tubular flowers are present, as e.g. in Senecio vulgaris (Groundsel), and the exterior of the capitulum is then as in the Eupatorieæ. The stylar branches are straight, more or less flat and short (Fig. 610).

A. Anthemideæ. Involucral leaves imbricate, generally membranous at the edge; pappus wanting, or at most a membranous margin to the calyx, but without hairs.

[+]. Chaff-like bracts on the receptacle are found in Anthemis (Chamomile), Anacyclus (A. officinarum), Achillea (Milfoil, Fig. 610), Santolina, etc.

[++]. A naked receptacle is found in the following: Bellis (Daisy) has solitary capitula on leafless stalks with white ray-flowers.—Matricaria (Wild Chamomile) has a conical receptacle. (M. chamomilla has a very high, hollow receptacle; M. inodora has large, odourless capitula, and the receptacle is not hollow.)—Chrysanthemum (Ox-eye) most frequently large, solitary capitula; flat receptacle.—Pyrethrum; pappus scanty.—With these are classed Tanacetum (Tansy) and Artemisia (Wormwood) with tubular corollas only.

B. Heliantheæ. Most frequently a bract to each flower is found on the receptacle. The pappus is never exactly hairy, but consists of scales, spines, etc., and the fruits are most frequently compressed (Fig. 606 c).—Helianthus (Sun-flower); H. tuberosus (Jerusalem Artichoke) has tuberous underground stems. Dahlia has tuberous roots (Am.). Bidens (Bur-marigold, Fig. 606 c); the fruits are compressed with 2 (or more) spines provided with reflexed barbs.—Calliopsis; Rudbeckia; Zinnia; Tagetes has united involucral leaves, and yellow, transparent oil-glands. Spilanthes, Galinsoga, Melampodium, Silphium (Compass-plant), Helenium, Gaillardia.

C. Calenduleæ have 1–2 rows of involucral leaves, a naked receptacle, and large, crescent-shaped, irregularly warted fruits, of different forms in the same capitulum; pappus absent (Fig. 605).—Calendula (Marigold); ray-flowers ♀, disc-flowers ♂.

D. Senecioneæ, have a fine, hairy, white pappus; no bracts, otherwise as in Anthemideæ. The involucral leaves are most frequently in 1–2 rows.—Senecio (Groundsel) has two whorls of involucral leaves, which most frequently have black tips, the external being much shorter than the internal ones (S. vulgaris has all flowers ☿ and alike).—Cacalia, Doronicum, Cineraria, Ligularia, Arnica (A. montana; large, long-stalked capitula; leaves opposite, forming a kind of rosette).

E. Astereæ have a bristle-like, unbranched pappus, often of a dingy brown; receptacle naked; involucral leaves numerous, imbricate.—Solidago (Golden-rod); capitula small, yellow-flowered, borne in panicles. Aster; disc-flowers most frequently yellow, ray-flowers violet; Callistephus; Erigeron (Flea-bane)—Inula.—All the corollas are tubular in: Gnaphalium (Cud-weed); involucral leaves dry, rattling, often coloured; the foliage-leaves and stem often white with woolly hairs; ray-flowers ♀, with narrow, tubular corolla; disc-flowers ☿ (few). Antennaria (Cat’s-foot; diœcious), Filago, Helichrysum, Ammobium, Rhodanthe and others. Leontopodium (L. alpinum, “Edelweiss”).

F. Ambrosieæ, a very reduced type of Compositæ, differing from the others in having free anthers; the capitula are generally unisexual, monœcious, the ♂ borne in a terminal inflorescence, the ♀ in the leaf-axils. In other respects they are most closely related to Heliantheæ.—Xanthium. In the ♂-capitula there are many flowers without calyx, but with tubular corolla and free involucral leaves. In the ♀-capitula there are only 2 flowers, which are entirely destitute of both calyx and corolla; involucral leaves 2-spined, united to form an ovoid, bilocular envelope, each compartment containing one flower. The envelope of involucral leaves unites with the fruits, enclosing them at maturity with a hard covering from which numerous hook-like spines project, assisting very greatly in the distribution of the fruit. The whole structure thus finally becomes a 1- or 2-seeded false nut.—Ambrosia, the ♀ capitulum 1-flowered.

Pollination. The flowers are somewhat insignificant, but become very conspicuous owing to a number being crowded together in one inflorescence. The corollas of the ray-flowers, being often very large (Astereæ; Centaurea), frequently render the capitula still more conspicuous. The capitula display many biological phenomena similar to those often shown by the individual flowers in other orders, e.g. by periodically opening and closing, in which the involucral leaves resemble the calyx in their action. (The name “Compositæ” originates from the term “flos compositus,” composite flower). An abundance of honey is formed, which to some extent fills up the corolla-tube, and since insects may visit a number of flowers in the course of a short period they are very frequently visited, especially by butterflies and bees. The pollination has been described on page 567. Protandry is universal. In the bud the tips of the styles, covered by the sweeping-hairs, lie closely enveloped by the anther-tube; in the next stage the style grows through the tube and sweeps out the pollen as it proceeds; ultimately the stylar branches expand and the stigma is then prepared to receive the pollen. In many, the sensitiveness of the filaments assists in sweeping out the pollen at the exact moment of the insect visit. Regular self-pollination is found e.g. in Senecio vulgaris; wind-pollination e.g. in Artemisia and the plants related to it.

This extremely natural and well-defined order is the largest (and no doubt one of the youngest?); it embraces 10–12,000 known species (in 770 genera), or about one-tenth of all Flowering-plants. They are distributed over the whole globe, but are most numerous in temperate countries; the majority prefer open spaces; a smaller number are forest-forms. They abound especially in open districts in America.

Among the substances frequently found may be mentioned: Inulin (especially in the subterranean parts), Bitter materials, Tannin, volatile oils, fatty oils in the fruits. Medicinal:[40] “Herba” of Artemisia absinthium (Wormwood) and maritima[+] (Sea-wormwood), Achillea millefolium; the leaves of Cnicus benedictus and Tussilago farfara; the unopened capitula of Artemisia maritima, var. stechmanniana; the capitula of Tanacetum, Matricaria chamomilla[+] (wild Chamomile), Anthemis nobilis[+] (common Chamomile); the separate flowers of Arnica; the roots of Arnica montana[+], Taraxacum officinale[+], Anacyclus officinarum[+], Lappa major, minor, nemorosa and tomentosa, Inula helenium and Artemisia vulgaris; the latex of Lactuca virosa[+]. The following are cultivated for food:—Lactuca sativa (Lettuce), Cichorium endivia (from E. Asia, for salads), Cynara scolymus (Artichoke, Mediterranean), Scorzonera hispanica (S. Eur.), Helianthus tuberosus (Jerusalem Artichoke, from N. Am., introduced into Europe 1616), Cichorium intybus (roots as “chicory,”) Tragopogon porrifolium (Salsafy), Artemisia dracunculus. Oil is extracted from the following (the seeds): Helianthus annuus (Peru), Madia sativa (Chili), Guizotia oleifera (Abyssinia). Dyes from: Carthamus tinctorius (Safflower, used in the preparation of rouge; Egypt), Serratula tinctoria. Insect-powder from: Pyrethrum cinerariifolium (Dalmatia) and roseum (Persia, Caucasus). The following are cultivated in houses and gardens for the sake of their scented leaves:—Tanacetum balsamita (Balsam), Artemisia abrotanum (Southernwood) and A. argentea. A great many of the genera enumerated are cultivated in dwelling-houses for the sake of the flowers; e.g. Pericallis cruenta (generally termed “Cineraria”). Asteriscus pygmæus is supposed to be the genuine “Rose of Jericho”; the involucral leaves envelop the fruits after their ripening and keep them enclosed for 8–10 months until rain occurs.