The SympetalÆ or GamopetalÆ are at once distinguished from the ChoripetalÆ by having the petals more or less united, so that the corolla is to some extent tubular. In the last order of the ChoripetalÆ we found a few examples (MimosaceÆ) where the same thing is true, and these form a transition from the ChoripetalÆ to the SympetalÆ. There are two great divisions, IsocarpÆ and AnisocarpÆ. In the first the carpels are of the same number as the petals and sepals; in the second fewer. In both cases the carpels are completely united, forming a single, compound pistil. In the IsocarpÆ there are usually twice as many stamens as petals, occasionally the same number. There are three orders of the IsocarpÆ, viz., Bicornes, PrimulinÆ, and DiospyrinÆ. The first is a large order with six families, including many very beautiful plants, and a few of some economic value. Of the six families, all but one (EpacrideÆ) are represented in the United States. Of these the PyrolaceÆ includes the pretty little pyrolas and prince’s-pine (Chimaphila) (Fig.116, J); the MonotropeÆ has as its commonest examples, the curious Indian-pipe (Monotropa uniflora), and pine-sap (M.hypopitys) (Fig.116, L). These grow on decaying vegetable matter, and are quite devoid of chlorophyll, the former species being pure white throughout (hence a popular name, “ghost flower”); the latter is yellowish. The magnificent rhododendrons and azaleas (Fig.116, F), and the mountain laurel (Kalmia) (Fig.116, I), belong to the RhodoraceÆ. Fig.116.—Types of Isocarpous sympetalÆ (Bicornes). A, flowers, fruit, and leaves of huckleberry, Gaylussacia (VaccinieÆ), ×1. B, vertical section of the flower, ×3. C, a stamen: i, from in front; ii, from the side, ×4. D, cross-section of the young fruit, ×2. E, flower of sorrel-tree, Oxydendrum (EricaceÆ), ×2. F, flower of azalea (Rhododendron), ×½. G, cross-section of the ovary, ×3. H, diagram of the flower. I, flower of mountain laurel (Kalmia), ×1. J, prince’s-pine, Chimaphila (PyrolaceÆ), ×½. K, a single flower, ×1. L, plant of pine-sap, Monotropa, (MonotropeÆ), ×½. M, section of a flower, ×1. The second order, the primroses (PrimulinÆ), is principally represented in the cooler parts of the world by the true primrose family (PrimulaceÆ), of which several familiar plants may be mentioned. The genus Primula includes the European primrose and cowslip, as well as two or three small American species, and the commonly cultivated Chinese primrose. Fig.117.—Isocarpous sympetalÆ (PrimulinÆ, DiospyrinÆ). A, shooting-star, Dodecatheon (PrimulaceÆ), ×½. B, section of a flower, ×1. C, diagram of the flower. D, Moneywort, Lysimachia (PrimulaceÆ), ×½. E, a perfect flower of the persimmon, Diospyros (EbenaceÆ), ×1. F, the same, laid open: section of the young fruit, ×2. H, longitudinal section of a ripe seed, ×1. em. the embryo. I, fruit, ×½. The sea-rosemary (Statice) and one or two cultivated species of plumbago are the only members of the plumbago family (PlumbagineÆ) likely to be met with. The remaining families of the PrimulinÆ are not represented by any common plants. The third and last order of the Isocarpous sympetalÆ has but a single common representative in the United States; viz., the persimmon (Diospyros) (Fig.117, E). This belongs to the family EbenaceÆ, to which also belongs the ebony The second division of the SympetalÆ (the AnisocarpÆ) has usually but two or three carpels, never as many as the petals. The stamens are also never more than five, and very often one or more are abortive. Fig.118.—Types of Anisocarpous sympetalÆ (TubiflorÆ). A, flower and leaves of wild phlox (PolemoniaceÆ), ×½. B, section of a flower, ×1. C, fruit, ×1. D, flower of blue valerian (Polemonium), ×1. E, flowers and leaf of water-leaf, Hydrophyllum (HydrophyllaceÆ), ×½. F, section of a flower, ×1. G, flower of wild morning-glory, Convolvulus (ConvolvulaceÆ), ×½. One of the bracts surrounding the calyx and part of the corolla are cut away. H, diagram of the flower. I, the fruit of a garden morning-glory, from which the outer wall has fallen, leaving only the inner membranous partitions, ×1. J, a seed, ×1. K, cross-section of a nearly ripe seed, showing the crumpled embryo, ×2. L, an embryo removed from a nearly ripe seed, and spread out; one of the cotyledons has been partially removed, ×1. The first order (TubiflorÆ) has, as the name indicates, tubular flowers which show usually perfect, radial symmetry (Actinomorphism). There are five families, all represented by familiar plants. The first (ConvolvulaceÆ) has as its type the morning-glory (Convolvulus) (Fig.118, G), and the nearly Fig.119.—Anisocarpous sympetalÆ (TubiflorÆ). A, inflorescence of hound’s-tongue, Cynoglossum (BorragineÆ), ×½. B, section of a flower, ×2. C, nearly ripe fruit, ×1. D, flowering branch of nightshade, Solanum (SolaneÆ), ×½. E, a single flower, ×1. F, section of the flower, ×2. G, young fruit, ×1. H, flower of Petunia (SolaneÆ), ×½. I, diagram of the flower. The third family (HydrophyllaceÆ) includes several species of water-leaf (Hydrophyllum) (Fig.118, E) and Phacelia, among our wild flowers, and species of Nemophila, Whitlavia and others from the western states, but now common in gardens. The last family (SolaneÆ) includes the nightshades (Solanum) (Fig.119, D), to which genus the potato (S.tuberosum) and the egg-plant (S.Melongena) also belong. Many of the family contain a poisonous principle, e.g. the deadly nightshade (Atropa), tobacco (Nicotiana), stramonium (Datura), and others. Of the cultivated plants, besides those already mentioned, the tomato (Lycopersicum), and various species of Petunia (Fig.119, H), Solanum, and Datura are the commonest. The second order of the AnisocarpÆ consists of plants whose flowers usually exhibit very marked, bilateral symmetry (Zygomorphism). From the flower often being two-lipped (see Fig.120), the name of the order (LabiatiflorÆ) is derived. Of the nine families constituting the order, all but one are represented within our limits, but the great majority belong to two families, the mints (LabiatÆ) and the figworts (ScrophularineÆ). The mints are very common and easily recognizable on account of their square stems, opposite leaves, strongly bilabiate flowers, and the ovary splitting into four seed-like fruits (Fig.120, D, F).
Fig.120.—Anisocarpous sympetalÆ (LabiatiflorÆ). A, dead nettle, Lamium, (LabiatÆ), ×½. B, a single flower, ×1. C, the stamens and pistil, ×1. D, cross-section of the ovary, ×2. E, diagram of the flower; the position of the absent stamen is indicated by the small circle. F, fruit of the common sage, Salvia (LabiatÆ), ×1. Part of the persistent calyx has been removed to show the four seed-like fruits, or nutlets. G, section of a nutlet, ×3. The embryo fills the seed completely. H, part of an inflorescence of figwort, Scrophularia (ScrophularineÆ), ×1. I, cross-section of the young fruit, ×2. J, flower of speedwell, Veronica (ScrophularineÆ), ×2. K, fruit of Veronica, ×2. L, cross-section of K. M, flower of moth-mullein, Verbascum (ScrophularineÆ), ×½. N, flower of toad-flax, Linaria (ScrophularineÆ), ×1. O, leaf of bladder-weed, Utricularia (LentibulariaceÆ), ×1. x, one of the “traps.” P, a single trap, ×5. The ScrophularineÆ differ mainly from the LabiatÆ in having round stems, and the ovary not splitting into separate one-seeded fruits. The leaves are also sometimes alternate. There are generally four stamens, two long and two short, as in the labiates, but in the mullein (Verbascum) (Fig.120, M), where the flower is only slightly zygomorphic, there is a fifth rudimentary Fig.121.—Anisocarpous sympetalÆ (LabiatiflorÆ). A, flowering branch of trumpet-creeper, Tecoma (BignoniaceÆ), ×¼. B, a single flower, divided lengthwise, ×½. C, cross-section of the ovary, ×2. D, diagram of the flower. E, flower of vervain, Verbena (VerbenÆ), ×2: i, from the side; ii, from in front; iii, the corolla laid open. F, nearly ripe fruit of the same, ×2. G, part of a spike of flowers of the common plantain, Plantago (PlantagineÆ), ×1; The upper flowers have the pistils mature, but the stamens are not yet ripe. H, a flower from the upper (younger) part of the spike. I, an older expanded flower, with ripe stamens, ×3. The curious bladder-weed (Utricularia) is the type of the family LentibulariaceÆ, aquatic or semi-aquatic plants which possess special contrivances for capturing insects or small water animals. These in the bladder-weed are little sacs (Fig.120, The family GesneraceÆ is mainly a tropical one, represented in the greenhouses by the magnificent Gloxinia and Achimenes, but of native plants there are only a few parasitic forms destitute of chlorophyll and with small, inconspicuous flowers. The commonest of these is Epiphegus, a much-branched, brownish plant, common in autumn about the roots of beech-trees upon which it is parasitic, and whence it derives its common name, “beech-drops.” The bignonia family (BignoniaceÆ) is mainly tropical, but in our southern states is represented by the showy trumpet-creeper (Tecoma) (Fig.121, A), the catalpa, and Martynia. The other plants likely to be met with by the student belong either to the VerbenaceÆ, represented by the showy verbenas of the gardens, and our much less showy wild vervains, also belonging to the genus Verbena (Fig.121, E); or to the plantain family (PlantagineÆ), of which the various species of plantain (Plantago) are familiar to every one (Fig.121, G, I). The latter seem to be forms in which the flowers have become inconspicuous, and are wind fertilized, while probably all of its showy-flowered relatives are dependent on insects for fertilization. The third order (ContortÆ) of the AnisocarpÆ includes five families, all represented by familiar forms. The first, the olive family (OleaceÆ), besides the olive, contains the lilac and jasmine among cultivated plants, and the various species of ash (Fraxinus), and the pretty fringe-tree (Chionanthus) (Fig.122, A), often cultivated for its abundant white flowers. The other families are the GentianaceÆ including the true gentians (Gentiana) (Fig.122, F), the buck-bean (Menyanthes), the Fig.122.—Anisocarpous sympetalÆ (ContortÆ). A, flower of fringe-tree, Chionanthus (OleaceÆ), ×1. B, base of the flower, with part of the calyx and corolla removed, ×2. C, fruit of white ash, Fraxinus (OleaceÆ), ×1. D, flower of pink-root, Spigelia (LoganiaceÆ), ×½. E, cross-section of the ovary, ×3. F, flower of fringed gentian, Gentiana (GentianaceÆ), ×½. G, diagram of the flower. H, flowering branch of dog-bane, Apocynum (ApocynaceÆ), ×½. I, vertical section of a flower, ×2. J, bud. K, flower of milk-weed, Asclepias (AsclepiadaceÆ), ×1. L, vertical section through the upper part of the flower, ×2. gy. pistil. p, pollen masses. an. stamen. M, a pair of pollen masses, ×6. N, a nearly ripe seed, ×1. The last family is the milk-weeds (AsclepiadaceÆ), which have extremely complicated flowers. Our numerous milk-weeds (Fig.122, K) are familiar representatives, and exhibit perfectly the peculiarities of the family. Like the dog-banes, the plants contain a milky juice which is often poisonous. Fig.123.—Anisocarpous sympetalÆ (CampanulinÆ). A, vertical section of the bud of American bell-flower, Campanula (CampanulaceÆ), ×2. B, an expanded flower, ×1. The stamens have discharged their pollen, and the stigma has opened. C, cross-section of the ovary, ×3. D, flower of the Carpathian bell-flower (Campanula Carpatica), ×1. E, flower of cardinal-flower, Lobelia (LobeliaceÆ), ×1. F, the same, with the corolla and sepals removed. an. the united anthers. gy. the tip of the pistil. G, the tip of the pistil, ×2, showing the circle of hairs surrounding the stigma. H, cross-section of the ovary, ×3. I, tip of a branch of cucumber, Cucurbita (CucurbitaceÆ), with an expanded female flower (). J, androecium of a male flower, showing the peculiar convoluted anthers (an.), ×2. K, cross-section of the ovary, ×2. The fourth order (CampanulinÆ) also embraces five families, but of these only three are represented among our wild plants. The bell-flowers (Campanula) (Fig.123, A, D) are examples Fig.124.—Anisocarpous sympetalÆ (AggregatÆ). A, flowering branch of Houstonia purpurea, ×1 (RubiaceÆ). B, vertical section of a flower, ×2. C, fruit of bluets (Houstonia coerulea), ×1. D, cross-section of the same. E, bedstraw, Galium (RubiaceÆ), ×½. F, a single flower, ×2. G, flower of arrow-wood, Viburnum (CaprifoliaceÆ), ×2. H, the same, divided vertically. I, flowering branch of trumpet honeysuckle, Lonicera (CaprifoliaceÆ), ×½. J, a single flower, the upper part laid open, ×1. K, diagram of the flower. L, part of the inflorescence of valerian, Valeriana, (ValerianeÆ), ×1. M, young; N, older flower, ×2. O, cross-section of the young fruit; one division of the three contains a perfect seed, the others are crowded to one side by its growth. P, inflorescence of teasel, Dipsacus (DipsaceÆ), ×¼. fl. flowers. Q, a single flower, ×1. R, the same, with the corolla laid open. The various species of Lobelia, of which the splendid cardinal-flower (L.Cardinalis) (Fig.123, E) is one of the most beautiful, represent the very characteristic family LobeliaceÆ. Their milky juice contains more or less marked poisonous properties. The last family of the order is the gourd family (CucurbitaceÆ), represented by a few wild species, but best known by the many cultivated varieties of melons, cucumbers, Fig.125.—Anisocarpous sympetalÆ (AggregatÆ). Types of CompositÆ. A, inflorescence of Canada thistle (Cirsium), ×1. B, vertical section of A. r, the receptacle or enlarged end of the stem, to which the separate flowers are attached. C, a single flower, ×2. o, the ovary. p, the “pappus” (calyx lobes). an. the united anthers. D, the upper part of the stamens and pistil, ×3: i, from a young flower; ii, from an older one. an. anthers. gy. pistil. E, ripe fruit, ×1. F, inflorescence of may-weed (Maruta). The central part (disc) is occupied by perfect tubular flowers (G), the flowers about the edge (rays) are sterile, with the corolla much enlarged and white, ×2. G, a single flower from the disc, ×3. H, inflorescence of dandelion (Taraxacum), the flowers all alike, with strap-shaped corollas, ×1. I, a single flower, ×2. c, the split, strap-shaped corolla. J, two ripe fruits, still attached to the receptacle (r). The pappus is raised on a long stalk, ×1. K, a single fruit, ×2. The last and highest order of the SympetalÆ, and hence of the dicotyledons, is known as AggregatÆ, from the tendency to have the flowers densely crowded into a head, which not infrequently is closely surrounded by bracts so that the whole inflorescence resembles a single flower. There are six families, The lower members of the order, e.g. various RubiaceÆ (Fig.124, A, E), have the flowers in loose inflorescences, but as we examine the higher families, the tendency for the flowers to become crowded becomes more and more evident, and in the highest of our native forms DipsaceÆ (Fig.124, P) and CompositÆ (Fig.125) this is very marked indeed. In the latter family, which is by far the largest of all the angiosperms, including about ten thousand species, the differentiation is carried still further. Among our native CompositÆ there are three well-marked types. The first of these may be represented by the thistles (Fig.125, A). The so-called flower of the thistle is in reality a close head of small, tubular flowers (Fig.125, C), each perfect in all respects, having an inferior one-celled ovary, five stamens with the anthers united, and a five-parted corolla. The sepals (here called the “pappus”) (p) have the form of fine hairs. These little flowers are attached to the enlarged upper end of the flower stalk (receptacle, r), and are surrounded by closely overlapping bracts or scale leaves which look like a calyx; the flowers, on superficial examination, appear as single petals. In other forms like the daisy and may-weed (Fig.125, F), only the central flowers are perfect, and the edge of the inflorescence is composed of flowers whose corollas are split and flattened out, but the stamens and sometimes the pistils are wanting in these so-called “ray-flowers.” In the third group, of which the dandelion (Fig.125, H), chicory, lettuce, etc., are examples, all of the flowers have strap-shaped, split corollas, and contain both stamens and pistils. The families of the AggregatÆ are the following: I.RubiaceÆ of which Houstonia (Fig.124, A), Galium (E), Cephalanthus (button-bush), and Mitchella (partridge-berry) are examples; II.CaprifoliaceÆ, containing the honeysuckles (Lonicera) (Fig.124, I), Viburnum (G), snowberry (Symphoricarpus), Fig.126.—AristolochiaceÆ. A, plant of wild ginger (Asarum), ×. B, vertical section of the flower, ×1. C, diagram of the flower. Besides the groups already mentioned, there are several families of dicotyledons whose affinities are very doubtful. They are largely parasitic, e.g. mistletoe; or water plants, as the horned pond-weed (Ceratophyllum). One family, the AristolochiaceÆ, represented by the curious “Dutchman’s pipe” (Aristolochia sipho), a woody twiner with very large leaves, and the common wild ginger (Asarum) (Fig.126), do not appear to be in any wise parasitic, but the structure of their curious flowers differs widely from any other group of plants. |