Part 67

Protandry is most frequently found in Saxifraga, with the stamens successively bending towards the gynœceum; protogyny is more rare. In other genera there is protogyny without any movement of the stamens; Chrysosplenium is homogamous.--About 300 species; mostly in temperate climates. Saxifraga is especially Alpine. S. crassifolia and other species, Hoteia japonica, Tellima, etc., are ornamental plants.

The following genera are allied to the Saxifragaceæ:--

=1.= Parnassia (about 14 species; P. palustris, Grass of Parnassus). The flower is slightly perigynous, and has S5, P5, 5 fertile sepal-stamens, and 5 petal-stamens, which are developed as barren staminodes, palmately-lobed, and (3–) 4 carpels united in a 1-locular ovary with (3–) 4 parietal placentæ. Capsule.--~Protandrous. The flower has a slightly oblique plane of symmetry, which is especially shown during its development and in the order of sequence in which the anthers dehisce: originally they lie closely round the gynœceum; the anthers dehisce extrorsely, first the one which is placed opposite the most external sepal (the 2/5 arrangement is very distinct in the calyx), the filament elongating so that the anther lies over the ovary, and this is followed successively by the 4 others in a zig-zag line; the filaments bend backwards after the pollen is shed and the anthers drop off, and the stigmas are not developed until this is completed. The barren stamens are palmately divided into an uneven number (7, 9, 11) of lobes, tapering from the centre towards the edge, and bearing apparently glandular tips; their gland-like appearance is supposed to allure flies to visit the flower, or they may act as a kind of fence which compels the insects to enter the flower in a certain way, and thus effect pollination; the honey is secreted on their inner side, and not by the gland-like tips.~

=2.= Adoxa moschatellina (Moschatel). This is a perennial, creeping herb; the horizontal rhizome has an unlimited growth, and bears, in a scattered arrangement, both foliage-leaves, and white, fleshy scale-leaves. The aerial stem bears 2 opposite foliage-leaves and a capitate inflorescence of 5 flowers, 4 placed laterally (in opposite pairs) and 1 terminally. The flower is semi-epigynous, the calyx gamosepalous, corolla absent. The stamens are divided to the base, so that each filament bears a bilocular anther. The style is free, deeply cleft. The terminal flower has 2 bracteoles, 4 sepals, 4 stamens, cleft to the base, and a 4-locular ovary. The bracts of the lateral flowers are displaced on the flower-stalk, as in Chrysosplenium, and united with the 2 bracteoles into a kind of 3-leaved involucre; these flowers have 5 sepals, 5 split stamens with 2-locular anthers, and a 5-locular ovary. 1 pendulous ovule in each loculus. Fruit a drupe, green-coloured, with 1–5 stones.--This plant, which would perhaps be best placed in a special order, has also been classed with the Araliaceæ and Caprifoliaceæ.

The following are also allied to this order: Escalloniaceæ (arborescent plants with simple, scattered, leathery leaves), Cunoniaceæ (arborescent with opposite leaves), Cephalotaceæ (with pitcher-like, insect-catching leaves; Australia; Fig. 489) and Francoaceæ. These have respectively 85, 107, 1 and 3 species.

FIG. 490.--Floral diagram.

FIG. 491.--Flower in longitudinal section.

FIG. 492.--Seeds in longitudinal section.]

Order 3. =Ribesiaceæ= (=Currants=). 5-stamened Saxifragaceæ with epigynous flowers.--Moderately sized shrubs with scattered, stalked and palminerved, and generally palmilobed leaves, with a large leaf-sheath. The flowers (Figs. 490, 491), most frequently borne in racemes, are regular, epigynous, and have often, above the ovary, a cup- or bell-shaped, or tubular prolongation of the receptacle, on which the sepals, petals and stamens are situated; they have 5 sepals (often large, coloured), 5 small, free petals, only =5= stamens (opposite the sepals) and a =2=-carpellate gynœceum with a unilocular ovary and 2 parietal placentæ bearing many ovules. The fruit is a berry, whose seeds have a fleshy and juicy outer covering (Fig. 492). ~In some species, for example Ribes grossularia, there is found an unbranched, or a 3–5-branched spine, very closely resembling the spiny leaves of the Berberis, but which, however, are emergences springing from the base of the petiole. Ribes has two kinds of branches: long-branches and dwarf-branches, the latter alone bearing the flowers.~--Ribes (Figs. 490–492). The blades of the leaf are folded or rolled together in vernation. R. alpinum is diœcious.

75 species; especially from the N. Temp. regions (especially N. Am.).--The receptacle secretes honey on its inner surface. The Gooseberry-flower is slightly protandrous, others are homogamous; insect-and self-pollination are found. The following are FRUIT BUSHES: R. nigrum (Black Currant), R. rubrum (Red Currant), R. grossularia (Gooseberry), originating in Northern Europe and Asia. ORNAMENTAL BUSHES: the North American R. aureum (Golden Currant) and R. sanguineum (Blood-red Currant), etc.

Order 4. =Hydrangeaceæ.= Shrubs, with simple, opposite leaves, without stipules; flowers generally epigynous, 4–5-merous (Fig. 493).--Hydrangea (H. hortensia, etc.). Shrubs from N. Am. and E. Asia; corolla often valvate. The inflorescence, as in the case of the inflorescence of Viburnum opulus (Guelder Rose), has often irregular, large, but barren flowers at the circumference, whilst the others are much smaller, regular and ☿; the barren flowers are mostly 4-merous; in these cases it is the calyx which is large and petaloid, while the other parts of the flower are more or less suppressed. The branches of the inflorescence appear to be partially devoid of floral-leaves, since they are displaced upon the main axis.--Philadelphus; racemes (with terminal flower), sepals 4 (valvate), petals 4 (twisted), stamens many, and carpels 4 (opposite the petals), forming a 4-locular ovary. The numerous stamens (20–30) occur by the splitting of the sepal-stamens and are often therefore placed in distinct bundles. Fruit a capsule. Ph. coronaria (Syringa, Mock Orange-blossom), from S. Eur., is a common ornamental shrub, as also is Deutzia (Fig. 493) from N. Am. and E. Asia. The latter has S5, P5, A5 + 5, G3.--About 70 species.

Order 5 (?). =Pittosporaceæ.= This order has its home especially in Australia (90 species). The flower has S5, P5, A5 (episepalous), G2 (3–5), most frequently a unilocular ovary with many ovules in 2 rows, borne on 2 parietal placentæ, or a bilocular ovary. Some have berries, others capsules. Pittosporum, Citriobatus, Sollya, Billardiera.

Order 6. =Hamamelidaceæ.= Flowers more or less epigynous, with S4, P0 or 4, 4 fertile sepal-stamens, and 4 barren petal-stamens, bilocular ovary with 1–2 ovules in each loculus. Fruit a capsule. Hamamelis: one species in Japan and one in N. Am. Fothergilla. Liquidambar: monœcious; flowers in capitula or spikes; ♂-flowers without perianth, stamens indefinite; ♀-flower: slight perianth, 2-locular ovary with many ovules. OFFICINAL: “Styrax-balsam,” which is obtained by boiling the bark of Liq. orientalis, from Asia Minor. Liquidambar and Parrotia are found as fossils in the Upper Oligocene; Hamamelis perhaps in the Chalk.

Finally two orders with very reduced flowers are included in this family.

Order 7. =Platanaceæ.= Trees, with large, scattered, palminerved and lobed leaves, and ochreate stipules; the buds are concealed in a hollow at the base of the petiole. The bark falls off in large scales. ♂-and ♀-flowers (monœcious) in crowded, spherical inflorescences which are placed at wide intervals on a terminal, thin, and pendulous axis. The flowers have an insignificant calyx and corolla; the ♂-flower has few stamens; ♀-flower, perigynous, with 4 free carpels, 1 pendulous, orthotropous ovule in each. Fruit a nut; endosperm absent. 5 species; frequently grown in avenues and parks. P. occidentalis (N. Am.); P. orientalis (W. Asia.).

Order 8. =Podostemaceæ.= Aquatic plants, especially in swiftly running water, with somewhat of an Alga-like, Moss-like, or thalloid appearance; they show themselves in many ways to be adapted to their mode of life and situations (having a dorsiventral creeping stem, the flowers sunk in hollows, a formation of haptera upon the roots, and thalloid assimilating roots and thalloid stems, etc.). Tropical; 100 species.

Family 20. =Rosifloræ.=

The leaves are scattered, stipulate, or have at least a well developed sheath, which is generally prolonged on each side into a free portion (“adnate stipules”). The flowers are regular, perigynous or epigynous. Calyx and corolla 5 (-4)-merous with the usual position. The corolla is always polypetalous. The stamens are present in very varying numbers (5–∞) and position, but always placed in 5-or 10-merous whorls; they are frequently 20 in 3 whorls (10 + 5 + 5; see Figs. 494, 502, 505); the nearer they are placed to the circumference, the longer they are; they are generally incurved in the bud, or even rolled up. The number of the carpels is from 1–∞; in most cases all are individually free (syncarp), and when they are united it is in every case with the ovaries only, whilst the styles remain more or less free (Pomaceæ, species of Spiræa). The seeds have a straight embryo, and usually no endosperm.

The perianth and stamens are most frequently perigynous on the edge of the widened receptacle; its form varies between a flat cupule and a long tube or a cup (Figs. 495, 496, 498, 499, 500); the carpels are situated on its base or inner surface, in some instances on a central conical elongation of the floral axis (Fig. 496). The carpels in Pomaceæ also unite more or less with the hollow receptacle, or this grows in and fills up the space between the carpels, so that a more or less epigynous flower is formed (Fig. 504).--The following numbers of stamens occur: 5, 10 (in 1 whorl), 15 (10 + 5), 20 (10 + 5 + 5), 25 (10 + 10 + 5), 30-50 (in 10-merous whorls)--compare the diagrams. The theoretical explanation of this relation of the 10-merous whorls and their alternation with the 5-merous whorls is not definitely determined; a splitting of the members of the 5-merous whorls may be supposed, but the development shows no indication of this, and it is not supported in any other way. Several genera have “gynobasic” styles, that is, the style springs from the base of the ovary (Fig. 497 A, B).

The Rosifloræ are on one side closely related to the Saxifragaceæ (especially through Spiræa) from which it is difficult to separate them, and to the Myrtifloræ; on the other side they are allied, through the Mimosaceæ with the large number of stamens, and through the Amygdalaceæ with its single carpel, to the Leguminosæ. The family begins with forms which have many-seeded follicles, and passes on the one side to forms with nuts and drupes in perigynous flowers, and on the other side to the Pomaceæ.

Order 1. =Rosaceæ.= Herbs or shrubs, generally with compound leaves and persistent (adnate) stipules, flower perigynous, gynœceum formed of many free (therefore oblique) carpels, syncarps with fruitlets of various kinds. The exceptions are noted under the genera.

=1.= SPIRÆEÆ (Fig. 495) has 2–many ovules in each ovary, while in the other groups there is generally only 1, and never more than 2 ovules in each loculus. There are generally 5 cyclic carpels and the fruit is 5 follicles, which are not enclosed by the receptacle. The majority are shrubs. Stipules are often wanting.--Spiræa (Meadow-Sweet). The flowers are generally borne in richly flowered inflorescences of various forms. The carpels, in some species, unite together and form a simple gynœceum with free styles (an approach to the Pomaceæ).--~Closely allied to Spiræa are the East Asiatic shrubs: Kerria japonica, which has solitary flowers, in this country nearly always double (the fruit a nut), and Rhodotypos kerrioides which has opposite leaves, a remarkable feature among the Rosifloræ; it has a 4-merous flower, a well developed disc inside the andrœcium, and a drupe. Closely allied also is Gillenia (N. Am.) differing chiefly in the ascending ovules, Spiræa having pendulous ovules, and a more tubular receptacle.~

The groups Quillajeæ and Neuradeæ form a transition from Spiræa to Pomaceæ. In the first group, which contains only trees or shrubs with generally simple leaves, the carpels are either free or united (into a capsule); in the second the receptacle unites with the carpels, which are themselves often united together; in this case, too, the fruit is a capsule. Quillaja (S. Am.); Exochorda (China).

=2.= POTENTILLEÆ (Figs. 494, 496, 497). The flower has an “epicalyx” (Fig. 494 C) alternating with the sepals and formed by their stipules which are united in pairs, and hence its leaves are often more or less deeply bifid. The receptacle is cupular and often quite insignificant. The sepals are valvate in the bud. The large number of fruitlets are achenes, borne on a well-developed convex portion of the receptacle (~the Ranunculeæ resemble the Potentilleæ, but have no epicalyx, no enlarged receptacle, and spirally-placed stamens~). Most of the species are herbs with dichasial inflorescences, often arranged in racemes.--Potentilla (Cinquefoil). The achenes are borne on a dry, hairy receptacle; the style is situated towards the apex of the ovary, and is not prolonged after flowering. Herbs with digitate, in some, however, pinnate leaves, and generally yellow flowers.--Comarum (Fig. 494) (Marsh Cinquefoil) forms, by its fleshy-spongy receptacle, a transition to the next genus.--Fragaria (Strawberry) (Fig. 496). The receptacle becomes finally fleshy, coloured, and falls off (biologically it is a berry); the numerous fruitlets (drupes with thin pericarp) have basal styles (Fig. 497); leaves trifoliate; long, creeping runners.--Geum (Avens) has a terminal style which after flowering elongates into a long beak, with the apex (after the uppermost part has been thrown off) bent back into a hook, thus furnishing a means of distribution for the fruits. Leaves pinnate.--~Dryas comprises 3 Arctic or Alpine species with simple leaves and solitary flowers, the calyx and corolla 8–9-merous, the fruit resembles that of Geum, but the styles become still longer and feather-like (a flying apparatus).~

FIG. 496.--Longitudinal section of flower.

FIG. 497.--A carpel, entire, and in longitudinal section.]

=3.= RUBEÆ. Rubus (Bramble) has the same form of receptacle as the Potentilleæ, but no epicalyx; the fruitlets are drupes, not enclosed by the persistent calyx. Most frequently shrubs or undershrubs with prickles (emergences), glandular bristles and compound leaves. In the Raspberry (R. idæus) the fruitlets unite together and detach themselves from the receptacle.

=4.= ROSEÆ. Rosa; the receptacle is hollow, ovoid and contracted beneath the insertion of the calyx (Fig. 498), ultimately fleshy and coloured; it encloses a large number of fruitlets which are achenes as hard as stones (“hip,” biologically a berry).--Shrubs with imparipinnate leaves and adnate stipules. ~The sepals show clearly the order of their development (a divergence of 2/5), the two outer ones on both sides are lobed, the third one on one side only, and the two last, whose edges are covered by the others, are not lobed at all. Prickles (emergences) are generally present and in some species are placed in regular order, being found immediately below each leaf (usually two) although at somewhat varying heights.~