Part 53

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.

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.~

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_).

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.~

A _ring-like nectary_ is found round the base of the style.

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.

APPENDIX ON THE CLASSIFICATION OF PLANTS.

BY M. C. POTTER.

The earliest systems of classification were derived from the properties and uses of plants; and it was not until some two centuries ago that any scientific grouping of plants was attempted. Aristotle and Theophrastus had adopted the groups of Trees, Shrubs and Herbs as the chief divisions of the Vegetable Kingdom, a system which persisted and was employed by Tournefort and Ray as late as the end of the 17th century. The arrangement by which these three divisions were separated into smaller divisions was often founded upon a single character, such as the formation of the corolla, the form of fruit, that of the calyx and corolla, etc. All these systems of classification which brought into close proximity plants distinguished by some one character alone, could only be considered as _artificial_, since plants related to one another would not necessarily be included in the same group. As the knowledge of the morphology, physiology, and reproduction of plants increased, such systems were recognised as unscientific, and it became the aim of botanists to establish a _natural_ system, founded upon mutual relationships, which would associate together _only_ those plants which are truly allied.

The following are some of the chief systems of classification which will show the gradual development of the natural system, and may be of service to students making use of this text-book.[41]

System of JOHN RAY (1703).

I. Herbæ. A. IMPERFECTÆ (Flowerless). B. PERFECTÆ (Flowering). _Dicotyledones_. _Monocotyledones._ II. Arbores. A. _Monocotyledones._ B. _Dicotyledones._