Part 80

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).

Family 36. =Aggregatæ.=

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.

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.