Part 57

Order =Cactaceæ= (=The Cacti=). The flower is epigynous, ☿, regular, and remarkable for its acyclic structure; there are, for instance, a large number of spirally-placed sepals and petals, which gradually pass over into one another, and which in some species, to a certain extent, arise from the walls of the ovary as in Nymphæa (Fig. 383 A, B). The petals are free; rotate, opening widely in Opuntia, Pereskia, and Rhipsalis; erect and united at their base into a shorter or longer tube in Cereus, Epiphyllum, Mammillaria, Echinocactus, Melocactus, and others (Fig. 369). Stamens numerous, attached to the base of the corolla; gynœceum formed of many carpels, with one style, dividing into a number of branches corresponding to the number of carpels; the ovary has one loculus with many parietal placentæ; the ovules are anatropous, on long and curved funicles. Fruit a berry with exendospermous seeds. The fruit-pulp is mainly derived from the funicles.--The external appearance of the Cactaceæ is very peculiar; Pereskia, which has thick and fleshy leaves (Fig. 368), deviates the least; foliage-leaves of the usual form are wanting in the other genera, or are usually very small, and quickly fall off and disappear (Opuntia), or are modified into thorns; the stem, without normal foliage-leaves,--so characteristic a feature in this order,--makes its appearance after the two normally developed cotyledons. The stems are fleshy, perennial, and may finally become woody. In some they are elongated, globose, pointed, and more or less dichotomously branched, e.g. in several of the Rhipsalis species, which live mostly as epiphytes on trees; in others, elongated, branched, globose, or, most frequently, more or less angular (prismatic) or grooved and provided with wings, and either columnar and erect (as much as about 20 metres in height and 1 metre in circumference, as in C. giganteus in New Mexico) or climbing by roots (Cereus and Rhipsalis-species); in others again, compressed, more or less leaf-like, often with a ridge in the centre (winged), branched and jointed: Epiphyllum, Phyllocactus, Opuntia, some species of Rhipsalis; others are thick, short, spherical or ovoid, unbranched or only slightly branched, and either studded with prominent warts (mammillæ) each of which supports a tuft of thorns (Fig. 368 A; Mammillaria and others) or with vertical ridges, separated by furrows (rows of mammillæ which have coalesced) in Melocactus, Echinocactus, Echinopsis (Fig. 369); at the same time the ovary in some is embedded in the stem so that leaves or leaf-scars, with tufts of thorns in their axils, may be observed on the ovary just as on the stem.--The flattened shoots of the Cactaceæ are formed in various ways, either by the compression of cylindrical axes (Opuntia) or, as in Melocactus, etc., from winged stems in which all the wings are suppressed except two.

The thorns are produced directly from the growing points of the axillary buds, and are modified leaves. The axillary bud is united at its base with its subtending leaf, which as a rule is extremely rudimentary; and these together form a kind of leaf-cushion, larger in some genera than in others. This leaf-cushion attains its highest development in Mammillaria, in which it is a large, conical wart (see Fig. 368 A), bearing on its apex the tuft of thorns and rudimentary lamina.--The seedlings have normal cotyledons and a fleshy hypocotyl.

All the species (1,000?) are American (one epiphytic species of Rhipsalis is indigenous in S. Africa, Mauritius and Ceylon), especially from the tropical table-lands (Mexico, etc.). Some species, especially those without thorns, as Rhipsalis, are epiphytes. Opuntia vulgaris, the fruits of which are edible, is naturalized in the Mediterranean. The cochineal insect (Coccus cacti) lives on this and some closely allied species (O. coccinellifera, etc.), particularly in Mexico and the Canary Islands. Several are ornamental plants.

Family 9. =Polycarpicæ.=

The flowers as a rule are ☿, regular and hypogynous; however in some orders they are unisexual, e.g. in the Myristicaceæ, or zygomorphic (in Monkshood and Larkspur in the Ranunculaceæ); in the Lauraceæ, (Fig. 386) for example, perigynous, and in Nymphæa (Fig. 383) even partially epigynous flowers are typical.--The flowers are acyclic in very many of the genera of the two first orders, if not completely so, at any rate in the numerous stamens and carpels, thus denoting an old type. It is a remarkable characteristic that in the majority of the orders the number 3 prevails in the calyx and corolla; the number 5 also occurs, but the number 2 is seldom met with. Most orders have a double perianth; chorisis does not occur, suppression is rare, and the parts of the flower are developed in acropetal succession. The most characteristic feature in the order is the free, one-leaved, as a rule numerous carpels (apocarpous gynœceum). The number of carpels in some of the last mentioned orders dwindles down to 1 (e.g. the Berberideæ and Myristicaceæ). The carpels in Nymphæaceæ become united into one pistil (syncarpous), a condition which we also find distributed among the other orders.

Endosperm occurs in almost all the orders (except e.g. Lauraceæ). The nutritive tissue in Cabombeæ and Nymphæeæ is chiefly perisperm.

Order 1. =Ranunculaceæ.= Nearly all are herbs (except Clematis). The leaves are scattered (except Clematideæ), they have a large sheath with broad base (no stipules), and are most frequently palminerved with palmate lobes. The flowers are hypogynous, with most frequently a well pronounced convex receptacle (Figs. 374 B, 380), ☿, regular (except Delphinium and Aconitum); their structure varies very much; in some the leaves are verticillate, in others arranged spirally; in others, again, both modes of arrangement are found. It is a characteristic feature that the various series of leaves (especially calyx and corolla) are not so distinct or so sharply divided as is usual. The leaves of the perianth are free, imbricate (except Clematideæ); stamens numerous, with most frequently extrorse anthers; gynœceum free, apocarpous (except Nigella and partly Helleborus), with 1 or several ovules (Figs. 373, 378, 379) borne on the ventral suture. The fruit is either a nut or a follicle (Actæa has berries). The seed has a large, oil-containing endosperm and a small embryo (Fig. 374).

The main axis generally terminates in a flower, and the lateral axes branch in a cymose manner (Fig. 371). The flowers show the following differences in construction: VERTICILLATE (EUCYCLIC), i.e. constructed all through of alternating whorls: Aquilegia (Fig. 370), Xanthorhiza, and sometimes Eranthis. SEMIVERTICILLATE (HEMICYCLIC) i.e. with sepals and petals in alternate whorls, and the others arranged spirally: Ranunculus (Fig. 371), Myosurus, Pæonia and several other genera entirely, or in certain species only. SPIRAL-FLOWERED (ACYCLIC) i.e. all the leaves are arranged spirally, so that sepals and petals do not alternate the one with the other, even though they are the same in number: Adonis (Fig. 372), Aconitum, Delphinium-species, Nigella-species, Helleborus. The leaves of the calyx are in this instance arranged on a spiral of 2/5; those of the corolla on 2/5, 3/8, 5/13 or 8/21, and stamens and carpels likewise on higher fractions of the same series.

The genera Caltha, Anemone, Thalictrum and Clematis have a single perianth, which is most frequently petaloid; it is thus apparent that the sepals are petaloid, and the leaves, which in other genera have developed as petals, are in these instances stamens. The calyx is similarly petaloid in the genera Helleborus, Eranthis, Nigella, Delphinium and Aconitum; but the petals are present in these instances in unusual (horn-like) forms, and almost entirely given up to the function of nectaries, a function they already possess in Ranunculus. According to a more recent theory the “honey-leaves” are transformed stamens, which have lost the function of reproduction; the perianth is then single, and most frequently petaloid. [Those leaves in the flowers of many Ranunculaceæ which bear nectaries are termed by Prantl honey-leaves, and comprise those leaf-structures of the flower whose essential function lies in the production of nectar, and which, independent of the differentiation of the perianth into calyx and corolla, are derived from the stamens by the loss of their reproductive functions. Clear transitional forms are found between the two series of the perianth (e.g. between the sepaloid and petaloid perianth-leaves of Anemone japonica, A. decapetala, Trollius-species) while transitional forms are never found between perianth-and honey-leaves (with the exception of Aquilegia vulgaris, var. stellata). In Anemone and Clematis the honey-leaves pass gradually into the stamens, and agree with the stamens in the other Ranunculaceæ in their arrangement, development, and scant system of veins (except Nigella). In Delphinium, sect. Consolida, the two honey-leaves placed in front of the unpaired perianth-leaf are united into one, as shown by the veins (twice three veins arranged symmetrically). The honey-leaves of Aquilegia, Callianthemum, and the majority of the Ranunculus-species serve by reason of their large circumference, as organs of attraction, and on this account are considered as petals by other authors.--The same position in the flower which the honey-leaves assume is found occupied by staminodes, without nectar, in some Coptis-species, in Anemonopsis, Actæa sect. Euactæa, (e.g. A. racemosa), Clematis sect. Atragene; in the last-named they closely surround the stamens, in Actæa they are petaloid.--A perianth, sharply differentiated into calyx and corolla, and destitute of honey-leaves, is found in Anemone, sect. Knowltonia (Cape),

Adonis, Pæonia.--The perianth of the Ranunculaceæ is considered by Prantl to be usually petaloid.--The nectaries arise in the Ranunculaceæ (1) on normal stamens (Clematis sect. Viorna), (2) on the honey-leaves (this is generally the case), and (3) on the carpels (Caltha and the majority of Trollius-species).--As the result of his researches upon the Ranunculaceæ, Prantl does not agree with the view advanced by Drude (Schenk, Hand. d. Bot. iii.) that the petals in general have proceeded from the metamorphosis of the stamens (K)].

The most primitive form of fruit is undoubtedly the pod formed by one carpel, on the edges of which (along the ventral suture) two rows of ovules are situated: Pæonieæ, Helleboreæ, Delphinieæ (Fig. 379). In a great many genera the number of ovules has been limited to one perfect one, which is placed in the central plane under the united leaf-edges, and sometimes also some barren ovules above it (Fig. 373). The fruitlets in this case become achenes, and are present in much larger numbers than when there are follicles.

The following have FOLLICLES: Pæonieæ, Helleboreæ (except Actæa) and Delphinieæ; ACHENES: Ranunculeæ, Anemoneæ and Clematideæ.

=A. Follicles= (Figs. 375, 379), with many ovules, situated in two rows along the ventral suture. ~Actæa has berries, Nigella has capsules of several loculi.~

=1.= PÆONIEÆ, PEONY GROUP. This has regular, acyclic flowers with a normal, most frequently 5-leaved, imbricate calyx; large, coloured petals, and introrse anthers. Slightly perigynous. Surrounding the base of the carpels a ring-like swelling of the receptacle (“disc”) is present, which is largest in P. moutan. The follicles are more or less fleshy or leathery. Mostly herbs, with pinnatisect or decompound leaves and large, solitary flowers; a gradual transition may be traced from the foliage-leaves to the petals. Pæonia; Hydrastis.

=2.= HELLEBOREÆ, HELLEBORE GROUP. This has regular flowers with most frequently a coloured calyx. The petals (honey-leaves) are modified into nectaries; they may be horn-like, provided with a spur, or of a similarly unusual form, or they may be entirely absent. Anthers often extrorse.--Trollius (Globe-flower). The flower is acyclic: many petaloid sepals, succeeding these, most frequently, several linear, dark yellow petals, which bear a naked nectary at the base; finally, many stamens and carpels arranged in a spiral (3/8, 8/21).--Caltha (Marsh-marigold, Figs. 375, 377); 5 (-7) yellow sepals, no petals. The foliage-leaves have a large amplexicaul sheath.--Helleborous (Hellebore) has pedate leaves. The flower is acyclic, with 5 large, regular, persistent, often petaloid sepals (2/5); small, horn-like petals (honey-leaves; most frequently 13, divergence 8/13) and generally few carpels (Fig. 374).--Coptis.--Isopyrum.--Eranthis (Winter Aconite), like Anemone, has a 3-leaved involucre and most frequently trimerous flowers, ~6 large petaloid sepals, 6 petals (tubular honey-leaves), 6 oblique rows of stamens, 3–6 carpels~. Aquilegia (Columbine, Fig. 376); the flower is entirely cyclic and has large spurs on all the 5 petals (funnel-shaped honey-leaves); S5 coloured, P5, A5 × (8–12), G5 in regular alternation (Figs. 376, 370); the innermost stamens are often staminodes (Fig. 370).--Nigella (Love-in-the-mist, Fig. 378) has 5 sepals and 8 small, two-lipped petals cleft at the apex (the nectary is covered by the under-lip; Fig. 378 C, D). The 5 carpels are more or less completely united; and a many-carpellate ovary with free styles is formed in some. Large air-chambers in the external wall of the ovary are formed in N. damascena (Fig. 378).--Actæa (Baneberry) has coloured sepals, either no petals or an indefinite number, and only 1 carpel. The fruit is a berry (or follicle).--~Cimicifuga, Garidella, Xanthorhiza (S5, P5, A5 + 5, G5).~

=3.= DELPHINIEÆ, LARKSPUR GROUP. Zygomorphic flowers with coloured calyx; the 2 posterior petals (honey-leaves) are transformed into nectaries, the others are small or absent altogether.--Aconitum (Monkshood); 5 sepals, of which the posterior one (Fig. 379 A) is helmet-shaped; most frequently 8 petals (as in Fig. 372), of which the two posterior ones (honey-leaves) are developed into long-clawed nectaries (Fig. 379 A, k) enveloped by the helmet-like sepal; the others are small, or are to some extent suppressed. ~Stamens on a spiral of 3/8–5/13; generally 3 carpels.~ Perennial herbs.--Delphinium (Larkspur); very closely allied to Aconitum, but the anterior 4 petals are most frequently wanting, and the 2 posterior ones have each a spur, which is enclosed by the posterior sepal, the latter being also provided with a membranous spur. ~Stamens and carpels arranged on a spiral of 3/8, 5/13, 8/21. In D. ajacis and consolida there is apparently only 1 petal (by the fusion of 4) and 1 carpel.~

=B. Fruit achenes.= Many carpels, each with only 1 ascending (Fig. 373 C), or pendulous (Fig. 373 D), perfect ovule; often also rudimentary ovules above it (Fig. 373 A, B). Fruit achenes.

=4.= RANUNCULEÆ, BUTTERCUP GROUP, has double perianth. Myosurus and Adonis have pendulous ovules as in Anemoneæ (Fig. 373 D); ~Ranunculus, with Batrachium and Ficaria, erect ovules (Fig. 373 C) and downwardly-turned radicle.~--Ranunculus. Most frequently S5, P5, many spirally-placed stamens and carpels (Figs. 371, 380). The petals (honey-leaves) have a nectary at the base, covered by a small scale. ~Batrachium, Water Ranunculus, deviates by the achenes being transversely wrinkled; dimorphic leaves. Ficaria has 3 sepals and 7–8 petals arranged in 2/5–3/8. F. ranunculoides (the only species) has tuberous roots, which spring from the base of the axillary buds, and together with these, serve as organs of reproduction. The embryo has only 1 cotyledon.~--Myosurus (Mouse-tail) has small prolongations from the 5 sepals; 5 narrow petals which bear the nectaries near the apex; sometimes only 5 stamens, and an ultimately very long receptacle, with numerous spirally-arranged achenes (Fig. 381).--Adonis is acyclic (Fig. 372); most frequently 5 sepals with a divergence of 2/5, 8 petals of 3/8, indefinite stamens and carpels of 3/8 or 5/13. The corolla has no nectary.

=5.= ANEMONEÆ, ANEMONE GROUP, has a single perianth. ~(Pendulous ovules (Fig. 373 D), radicle turned upward).~--Anemone has a single, petaloid, most frequently 5–6-leaved perianth, and beneath the flower most frequently an involucre of 3 leaves, placed close together in the form of a whorl. In A. nemorosa, ranunculoides, etc., the involucral leaves resemble foliage-leaves; in A. hepatica they are situated close under the perianth, and resemble sepals, and in the sub-genus Pulsatilla they stand between the foliage-leaves and floral-leaves. The style of Pulsatilla finally grows out in the form of a feather. ~The main axis of A. hepatica has unlimited growth (it is biaxial), and the flowers are borne laterally in the axils of the scale-leaves; in the others (uniaxial) the flower is terminal, and the rhizome becomes a sympodium after the first flowering.~--Thalictrum (Meadow Rue) has no involucre; 4–5-leaved, greenish perianth. The receptacle is flat. ~The stamens are brightly-coloured and have long filaments; 1–5 accessory flowers may occur in the leaf-axils of the panicle-like inflorescence.~

=6.= CLEMATIDEÆ, CLEMATIS GROUP. This differs from all the others in the valvate æstivation of the calyx and its opposite leaves. There are 4 (-several) petaloid sepals; petals are absent, or linear (Atragene). Ovule 1, pendulous. Achenes, often with prolonged, feathery style. The majority of the genera are shrubs, and climb by their sensitive, twining leaf-stalks.--Clematis; Atragene.

POLLINATION. The flowers are conspicuous either by coloured petals (honey-leaves) (Ranunculus, Pæonia) or coloured sepals (Helleborus, Anemone, Caltha, etc.), or by both (Aquilegia, Delphinium), or by the coloured stamens (Thalictrum). Some have no honey (Clematis, Anemone, Thalictrum), and are generally visited by insects for the sake of their pollen. Others have nectaries on the corolla (Ranunculus, Trollius, Helleborus, Nigella, Aconitum, etc.), more rarely on the stamens (Pulsatilla, Clematis-species), or the carpels (Caltha), or the calyx (certain species of Pæonia). The honey is readily accessible in the flat, open flowers, and these flowers also may easily pollinate themselves. There is marked protandry where the honey lies deeply hidden, as in Aquilegia, Delphinium, and Aconitum. Helleborus and some Ranunculus-species are protogynous.

About 680 species; especially in northern temperate climates, and extending to the Polar and Alpine regions. Only the Clematideæ are tropical.

The order has an abundance of acrid, vesicant properties (R. acer, sceleratus, etc.), and poisonous alkaloids (Helleborus niger is poisonous). OFFICINAL: Aconitum napellus (aconitine; leaves and tuberous roots); the rhizome of Hydrastis canadensis from N. Am. (the alkaloid hydrastine). The order, however, is best known for its ornamental plants; almost all the genera have species which are cultivated for their beauty. Sweet-scented flowers are absent.

Order 2. =Nymphæaceæ (Water Lilies).= WATER PLANTS; generally with large, floating leaves, and large solitary flowers; sepals 3–5, petals 3–∞, stamens 6–∞, carpels 3–∞. The flower is hypogynous, but in the Nymphæeæ different degrees of epigyny are found, and from this fact, as well as from the carpels being united into one pistil, the family forms a lateral offshoot from the Ranunculaceæ, with much greater modification. The seed often has an aril, and, in the majority, a farinaceous nutritive tissue, partly endosperm, partly perisperm (Fig. 383 C). The embryo has 2 thick cotyledons and a small hypocotyl; the plumule is well developed, with 2–4 leaves.

1. CABOMBEÆ. 3–4 species (Tropical S. Am.), resembling the Water Ranunculus, with two kinds of leaves, the submerged being dissected and the aerial peltate. The flowers are eucyclic, trimerous, with 2–3 free, epigynous carpels. The ovules are situated on the central line of the carpel--an almost unique circumstance. Endosperm and perisperm. Cabomba; Brasenia.

2. NELUMBONEÆ. The leaves are peltate, raised on long stalks high above the water. Large, hypogynous flowers (Fig. 382); sepals 4–5; petals numerous; stamens numerous; carpels several, distinct. The receptacle is very remarkable, being raised above the stamens, and developed into an inverted conical body on the apex of which the nut-like fruits are embedded in pits. Endosperm is wanting, but the embryo is large and has well developed cotyledons.--~Nelumbo, 2 species. N. lutea (N. Am.); N. speciosa (E. Ind.) was sacred amongst the ancient Hindoos and Egyptians, (the Lotus flower); its seeds are used as food.~

3. NYMPHÆEÆ, WATER LILY GROUP. The carpels are united into one, many-locular ovary, whose numerous ovules are situated on the surface of the partition walls (as in the Poppies); the stigma is sessile and radiating, the number of rays corresponding to the number of carpels (Fig. 383). The fruit is a spongy berry with many seeds, which have a large perisperm in addition to the endosperm (Fig. 383 C).

Sepals, petals, and stamens often pass gradually over the one into the other, the petals becoming narrower by degrees, and bearing anthers on each side of the apex, which gradually become larger anthers in proportion to the filament, until the perfect stamen is developed. The long-stalked leaves are floating, and most frequently cordate, elliptical, leathery, with a shiny surface, sometimes (as in Victoria regia and Euryale ferox) with strongly projecting thorny ribs on the lower surface. In the intercellular passages of the leaves are some peculiar, stellate cells.