Fig. 541.—A fruit of Myzodendron brachystachyum (slightly mag.) germinating on a branch.
Order 2. Santalaceæ. Parasites containing chlorophyll, which, by the help of peculiar organs of suction (haustoria) on their roots, live principally on the roots of other plants. Some are herbs, others under-shrubs. The regular, most frequently ☿-flowers have a simple perianth, which is gamophyllous, 3- or 5 partite with the segments valvate in the bud, and a corresponding number of stamens opposite the perianth-leaves. In the inferior ovary there is a free, centrally placed, often long and curved placenta with three ovules (one opposite each carpel); these are naked, or in any case have an extremely insignificant integument. Fruit a nut or drupe. Seed without testa. Endosperm fleshy. 225 species; chiefly in the Tropics.—Thesium, a native, is a herb with scattered, linear leaves and small 5-merous flowers (P5, A5, G3) in erect racemes; the subtending bracts are displaced on the flower-stalks. Fruit a nut.—Osyris (diœcious shrub; 3-merous flowers) is another European genus.—Santalum album, which grows in E. Ind., yields the valuable, scented Sandalwood, the oil of which is used medicinally.—Quinchamalium.
Myzodendron is a reduced form of the Santalaceæ; the ♂-flowers are without perianth; the perianth of the ♀-flower is 3-merous. About 7 species; S. Am.; parasitic on a Beech (Nothofagus). The fruit has 3 feathery brushes, alternating with the lobes of the stigma, which serve as flying organs and to attach the fruits to a branch (Fig. 541), the brushes twining round as soon as they come in contact with it. There is only 1 seed in the fruit, which germinates by a long, negatively heliotropic hypocotyl, and is attached by a radicle modified into an haustorium.
Order 3. Loranthaceæ (Mistletoes). Plants containing chlorophyll which are parasites on trees, and most frequently have opposite, simple, entire leaves and regular, epigynous, often unisexual, 2- or 3-merous flowers, with single or double perianth. Stamens equal in number and opposite to the perianth-leaves, free, or in varying degrees united to one another. The inferior ovary is constructed as in the Santalaceæ, the ovules being situated on a low, free, centrally-placed placenta, but the placenta and ovules unite with the wall of the ovary into one connected, parenchymatous mass, in which the embryo-sacs are imbedded. Only 1 (less frequently 2–3) of the 1–6 embryo-sacs is fertile. The number of the carpels however varies. The fruit is a 1-seeded berry, whose inner layer is changed into a tough slimy mass (bird-lime), which serves to attach the fruits to other plants.
The two groups, Loranthoideæ and Viscoideæ, are distinguished by the fact that the former has a distinct “calyculus,” i.e. an entire or lobed, or dentate swelling on the receptacle below the perianth. The majority of the Loranthoideæ have a petaloid perianth; in all the Viscoideæ, on the other hand, it is sepaloid.
Fig. 542.—Viscum album: A branch with leaves and berries: a scale-leaves; b foliage-leaves; n m n flowers; B seedling, the bark of the branch being removed; C an older embryo which still retains the cotyledons.
Fig. 543.—To the left the Rafflesiaceous Cytinus hypocistus, parasitic on the roots of Cistus. To the right the Balanophoraceous Cynomorium coccineum, parasitic on the roots of Salicornia.
The Mistletoe (Viscum album, Fig. 542) is a native, evergreen plant which may be found growing on almost any of our trees (sometimes on the Oak), and, like other Loranthaceæ, it produces swellings of the affected branches. Its spherical white berries (Fig. 542 A) enclose (1–) 2–3 green embryos; they are eaten by birds (especially Thrushes), and are partly sown with their excrement, partly struck or brushed off the branches of the trees, the seed being enclosed, at maturity, by viscin, i.e. “bird-lime.” The seeds may also germinate on the branches, without having first passed through the alimentary canal of the birds. On germination, the hypocotyl-axis first appears, as in Fig. 541, and bends towards the branch; the apex of the root then broadens, and forms at the end a disc-like haustorium, from the centre of which a root-like body grows through the bark into the wood, and ramifies between the bark and wood. Suckers are developed on the root like strands which are formed in this manner, without, however, having a rootcap; they are green, and penetrate the wood by the medullary rays (Fig. 542 C). Adventitious buds may also be developed from the root-like strands which break through the bark and emerge as young plants. The young stem quickly ceases its longitudinal growth, and lateral shoots are developed from the axils of its foliage-leaves. These and all following shoots have a similar structure; each of them bears a pair of scale-leaves (Fig. 542 A, a) and a pair of foliage-leaves (Fig. 542 A, b), and then terminates its growth, if it does not produce an inflorescence; new lateral shoots proceed from the axils of the foliage-leaves, and the branching, in consequence, is extremely regular and falsely dichotomous. Only one internode (shoot-generation) is formed each year, so that each fork indicates one year. The foliage-leaves fall off in the second year. The inflorescence is a 3(-5)-flowered dichasium (Fig. 542 A, m is the central flower, n the lateral). The plants are diœcious; the ♂-flower as a rule is 2-merous: perianth 2 + 2, each leaf of which bears on its inner side 6–20 pollen-sacs, each of which opens by a pore; this relationship may be considered to have arisen from the union of the perianth-leaves with the multilocular stamens (2 + 2) placed opposite them. The ♀-flowers always have Pr 2 + 2, G2.—Loranthus is also found in Europe (it has a 3-merous flower), especially in the central and south-eastern districts, on Quercus cerris and Q. pubescens; but the great majority of the 520 species grow in the Tropics on trees which they ornament with their often brightly-coloured flowers, and ultimately kill when present in too great numbers. The pollination in the numerous Loranthaceæ with unisexual flowers, is effected by the wind. In Viscum album this takes place in autumn, the actual fertilisation in the following spring, and the maturity in November or December; in the succeeding month of May the berry is ready to germinate, and falls off.
Uses. Birdlime from Viscum album.
Order 4. Rafflesiaceæ and Order 5. Balanophoraceæ. These orders comprise root-parasites, almost entirely devoid of chlorophyll; they are reddish or yellow, without foliage-leaves (Fig. 543). As far as our knowledge of these rare tropical plants extends, they have thalloid organs of vegetation resembling the root-like strands of Viscum, or they are filamentous and branched like Fungus-hyphæ; they live in and on the tissues of the host-plant, from which their flowering-shoots, often of mushroom-like form, are subsequently developed (Fig. 543). In order to unfold they must often break through the tissues of the host-plant.
Of the Rafflesiaceæ, Cytinus hypocistus is found in S. Europe living on roots of Cistus-plants and to some extent resembling Monotropa (Fig. 543). Rafflesia is the best known; it lives on roots of Cissus-species (belonging to the Ampelidaceæ) in Java; its yellowish-red, stinking flowers attain a gigantic size (one metre or more in diameter), and are borne almost directly on the roots of the host-plant. Besides these there are other genera: Brugmansia, Pilostyles, Hydnora.—To Balanophoraceæ (Fig. 543) belong: Balanophora, Langsdorffia, Scybalium, Sarcophyte, Helosis, etc., and in S. Europe, Cynomorium coccineum.
Sub-Class 2. Sympetalæ.
The characters which separate this from the first Sub-class, the Choripetalæ, have been described on page 336. They consist in the following: the flower is always verticillate, generally with 5 sepals, 5 petals, 5 stamens, and 2 carpels (in the median plane), the calyx is generally persistent and gamosepalous, the corolla is gamopetalous and united to the stamens, which are therefore adnate to it, the ovules have only one thick integument and a small nucellus. (The exceptions are noted later.)
This Sub-class is no doubt more recent than the Choripetalæ; it is also peculiar in including fewer trees and shrubby forms than the latter.
The Sympetalæ may be separated into 2 sections:—
A. Pentacyclicæ (five-whorled). The flowers in this section have 5 whorls equal in number, namely, 2 staminal whorls in addition to the calyx, corolla, and carpels; in some instances, one of the staminal whorls is rudimentary or entirely suppressed, but in this case it is frequently the sepal-stamens which are suppressed, and the whorl which is present stands opposite the petals. The flowers are regular. The number of carpels equals that of the sepals, but in one of the orders (Bicornes) they are opposite the petals (the flower being obdiplostemonous); in the other two orders (Primulinæ and Diospyrinæ) they are placed opposite the sepals (the flower being diplostemonous). This section is the most closely allied to the Choripetalæ, since the petals may sometimes be found entirely free, and the stamens inserted directly on the receptacle (Ericaceæ); ovules with two integuments are also found. It is very doubtful, whether the orders included under this head have any relationship with the other Sympetalæ. They appear in any case to represent older types.
B. Tetracyclicæ (four-whorled). The flowers have only 4 whorls, namely, beside sepals, petals, and carpels, only one whorl of stamens, which alternates with the petals; there is no trace of the second staminal whorl, and when the number of carpels is the same as that of the preceding whorls (“isomerous”) they alternate with the stamens; but in most cases there are 2 carpels placed in the median plane (see the diagrams, e.g. Figs. 559, 567, 583, 590, etc.). This section is the largest, and the one which shows the characteristics of the Sympetalæ best. Very irregular flowers are met with.
The following families belong to the Pentacyclicæ: 26, Bicornes; 27, Diospyrinæ; 28, Primulinæ.
The remaining families belonging to the Tetracyclicæ are:—
a. Hypogynous flowers (with a few exceptions): 29, Tubifloræ; 30, Personatæ; 31, Nuculiferæ; 32, Contortæ.
b. Epigynous flowers: 33, Rubiales; 34, Dipsacales; 35, Campanulinæ; 36, Aggregatæ. The ovaries and ovules in the last family are always reduced to one; and at the same time the fruits become nuts, and the flowers are united into crowded inflorescences.
A. Pentacyclicæ.
Family 26. Bicornes.
This family is chiefly composed of shrubs, less frequently of small trees, or perennial herbs; their leaves are undivided, most frequently evergreen, stiff and leathery, and always without stipules. The flowers are ☿ and regular, rarely slightly zygomorphic, most frequently obdiplostemonous, and 4- or 5-merous through all the 5 whorls. The stamens are attached to the receptacle, and as a rule are quite free from the petals, an attachment which is very rare among the Gamopetalæ. They have a simple gynœceum with one undivided style, a commissural stigma, and a multilocular ovary, whose axile placentæ project considerably into the loculi, and bear a large number of ovules. The placentæ are sometimes not united, and in consequence, the ovary is 1-locular with incomplete partition-walls, e.g. Pyrola, Monotropa. Embryo straight, with endosperm. The carpels are placed opposite the petals.
The diagram is generally Sn, Pn, An + n, Gn, in which n is 4 or 5. To this may be added, that the corolla is in most cases gamopetalous, but in some (especially Pyrolaceæ) perfectly polypetalous; and that the anthers usually open by pores, and often have two horn-like appendages (hence the name “Bicornes”) (Figs. 545, 546); frequently the two halves of the anther are also widely separated from each other at the upper end, so that the pores are placed each one at the end of its own tube (Fig. 546); the pollen-grains in the majority are united into tetrads (Fig. 542 D).—The flowers, as a rule, are pendulous and borne in racemes, coloured (red or white), but odourless. When the fruit is a capsule, the placenta with the seeds attached persists as a central column. A mycorhiza occurs on many.
The majority of plants belonging to this family inhabit cold and temperate countries, or high mountains in tropical regions; they prefer cold and dry or damp places (bogs, heaths, etc.). Plentiful in N. America.
Order 1. Pyrolaceæ. Perennial herbs; petals most frequently quite free from each other, and falling off singly after flowering; the anthers are without appendages, and open by pores (Fig. 544), or by a transverse slit. The placentæ are thick. The seeds in the capsule-like fruit (loculicidal dehiscence) are exceedingly small and light, they have a sac-like testa which loosely envelops them, an oily endosperm, and an extremely simple embryo, which consists only of an ellipsoidal, cellular mass, without cotyledons or differentiation into plumule and radicle.
Pyrola (Winter-green) is green, and has also large evergreen foliage-leaves. The flowers, 5-merous, are most frequently borne in racemes without a terminal flower; the anthers are extrorse in the bud with the pores in the lower portion (Fig. 544 A), but they become inverted at a later period, so that the pores open at the top (Fig. 544 C). P. uniflora has a single, terminal flower; it winters by its roots, producing from these in the spring aerial, quite unbranched shoots. Chimaphila umbellata.
Fig. 544.—Pyrola minor: A portions of a young flower; B the stigma; C portions of an older flower (longitudinal section).
Monotropa (Yellow Bird’s-nest) is very pale yellow, without chlorophyll, succulent, and has only scale-like leaves closely pressed upon the stem; it is a saprophyte. The raceme has a terminal flower, and is pendulous before flowering. The anthers open by a semicircular, transverse cleft. M. hypopitys reproduces chiefly by root-shoots.
About 30 species, especially N. Europe, N. America, and N. Asia.
Order 2. Ericaceæ. The flower (Fig. 545) is hypogynous, the median sepal posterior; corolla, gamopetalous; the stamens are generally 2-horned, and the fruit is a capsule, less frequently a berry or drupe. At the base of the ovary is a nectar-secreting disc (Fig. 545 B). This order comprises shrubs or undershrubs (rarely small trees), which are evergreen, and as a rule have densely crowded leaves.
1. Ericeæ, Heath Group. Flowers most frequently 4-merous (S4, P4, A4 + 4, G4, united in a 4-locular gynœceum), rarely 5-merous. The withered corolla persists after flowering. The leaves are most frequently acicular, opposite or verticillate; the buds are without scales. The fruit is a capsule.—Calluna (C. vulgaris, Ling) has a deeply 4-cleft corolla, which is less than the coloured calyx; capsule with septicidal dehiscence.—Erica (about 420 species; E. tetralix, Cross-leaved Heath) has a tubular or bell-shaped, 4-dentate corolla, which is much longer than the calyx. Capsule with loculicidal dehiscence.—Pentapera.
2. Andromedeæ. The flowers are 5-merous (S5, P5, A5 + 5, G5), with deciduous corolla. Capsule with loculicidal dehiscence. The leaves are scattered, and incline more to the ordinary broad-leaved forms.—Andromeda; Gaultheria; Cassandra (Lyonia); Cassiope.
Fig. 545.—Arctostaphylos uva-ursi.
3. Arbuteæ. The flowers as in the preceding group (Fig. 545), but the fruit is a berry or drupe. Arctostaphylos (A. uva-ursi, Bear-berry) has a drupe with 5 stones in a dry, farinaceous pulp; in other species there is 1 stone with several loculi. Arbutus (A. unedo, Strawberry-tree) has a spherical berry.
Pollination is effected by means of insects, especially by bees. The pollen is light and dry, and is shaken out through the pores of the anthers when the insects agitate the horn-like appendages during their visits. Self-pollination takes place, no doubt, in many cases.—800 species; the very large genus, Erica, especially in S. Africa (the Cape).—Officinal: the leaves of Arctostaphylos uva ursi. Arbutus unedo (S. Europe) has an edible, peculiarly warted (strawberry-like) fruit. Many Erica-species are cultivated as ornamental plants.
Order 3. Rhodoraceæ (Rhododendrons). This differs from the preceding order in the median sepal being anterior, and hence the position of the other floral whorls is also reversed. The flower is hypogynous, in most cases 5-merous; the corolla is most frequently deeply cleft or polypetalous, and falls off after flowering; the anthers open by pores, and have no horn-like appendages. Capsule with septicidal dehiscence.—The shrubs or small trees belonging to this order have, like the Vaccineæ, ordinary foliage-leaves, and the buds are generally provided with large bud-scales.
Rhododendron has 10 stamens, and a slightly zygomorphic flower with deeply 5-cleft corolla (the section Azalea has frequently only 5 stamens, the petal-stamens being absent). They are Alpine plants (200 species) in the mountains of Asia, especially the Himalayas; some in S. Europe.—Menziesia.—Ledum; small, rusty-brown, hairy shrubs with polypetalous, expanded, star-like corolla.—Kalmia (N. Am.) has a cupular corolla, with 10 small, pocket-like depressions in which the anthers are concealed until the arched, elastic filaments are freed from this position by means of the insects, when they quickly straighten themselves in the centre of the flower.—Phyllodoce; Loiseleuria (5 stamens); (Clethra (?); also placed among the Ternstrœmiaceæ).
About 270 species. Several species are ornamental plants. Several plants of the order are more or less narcotic. Ledum palustre has been used as a substitute for hops.
Order 4. Diapensiaceæ. Hypogynous flower. 3 floral-leaves beneath the flower (S5, P5, A5 + 0, G3). Stamens on the throat of the corolla. Pollen-grains single. Disc absent. Capsule loculicidal.—9 species from the Arctic regions. It is doubtful whether this order should be included in the Bicornes; perhaps it would be more correctly assigned to the Polemoniaceæ.
Order 5. Epacridaceæ. This order comprises those species of the family which are confined to Australia and the South Sea Islands. They are shrub-like plants, resembling the Ericaceæ in habit, in the inflorescence, and in the structure, form, and colour of the flower. They differ especially in having only 1 whorl of stamens (placed opposite the sepals) and in the anthers having only 2 loculi, and opening by a longitudinal slit. Fruit most frequently a drupe (or loculicidal capsule). Epacris-and Styphelia-species are ornamental plants. About 325 species.
Order 6. Vacciniaceæ (Bilberries). The flower (Fig. 546) is epigynous, the corolla gamopetalous, and the fruit a berry. The latter is most frequently spherical, and bears on its apex the calyx, which is generally very low, almost entire, and with a disc-like expansion inside. The flower is 4- or 5-merous (Fig. 546 B, D). The anthers have 2 pores, and are most frequently 2-horned (Fig. 546 F, G). Small shrubs; the leaves are scattered, not needle-like.
Vaccinium (Bilberry, Whortleberry) has an urceolate, gamopetalous, only slightly dentate corolla, and horn-like appendages to the anthers (Fig. 546). V. vitis idæa (Cowberry) is evergreen, with flowers in racemes, and bright red berries; V. myrtillus (Bilberry) and V. uliginosum (Bog Whortleberry) both have black berries with a blue bloom, leaves deciduous.—Oxycoccus has a polypetalous corolla with the petals projecting backwards. Anthers without appendages. O. palustris (Cranberry) has a slender, creeping stem, and is evergreen. Dark red berry.
Pollination essentially the same as the preceding order.—320 species; especially in N. Am. Some are useful on account of their edible fruits, especially Vaccinium myrtillus and V. vitis-idæa, and in a less degree Oxycoccus, etc. The fruits of V. myrtillus are officinal.
Fig. 546.—Vaccinium uliginosum (var. microphyllum). The parts of the flower A-E are enlarged 5–6 times; C and E are longitudinal sections; B and D the flower seen from above; F and G a stamen seen from the back and front; H the style and stigma.
Family 27. Diospyrinæ.
The flowers are regular, gamopetalous, typically diplostemonous, with the same number throughout all 5 whorls, thus: Sn, Pn, An + n, Gn, where n most frequently =5 (4–6), rarely 3, 7 or 8. Of the two whorls of stamens the one opposite the sepals is often present only as rudiments or is entirely suppressed, and the completely developed stamens are thus placed opposite the petals. The carpels are generally placed opposite the sepals. The ovary is multilocular with the ovules attached in the inner angles. The fruit is most frequently a berry. The seeds are large, generally solitary, or a few in each loculus.—All plants belonging to this family are trees or shrubs with scattered, single, most frequently entire, penninerved and leathery leaves without stipules; the majority are tropical (America, Asia), some are found in N. Am. and the Mediterranean.
Order 1. Sapotaceæ. Plants with latex; anthers extrorse, 1 erect ovule in each loculus; fruit a berry; the seeds with bony, shiny brown testa have a large, lateral hilum. The leaves are frequently covered with silky hairs.—A useful order in several respects (400 tropical species). The wood of some genera, such as Sideroxylon (Iron wood) and Bumelia, is as hard as iron. The latex of Palaquium (P. oblongifolium, P. gutta, and other species), Mimusops and Payena (Sumatra, E. Ind.), is the raw material of gutta percha. The following have very delicious fruits: Lucuma mammosa, Achras sapota, Chrysophyllum cainito (Star-apple), etc. The seeds of Bassia (E. Ind.) contain a large quantity of a fatty oil. Isonandra, Mimusops schimperi are often found in the Egyptian royal tombs.
Order 2. Ebenaceæ. Plants without latex, often diœcious; flowers with a more or less leathery perianth. The number of stamens is sometimes increased (by splitting?); ovules 1–2, pendulous in each loculus. Fruit a berry.—250 species; chiefly tropical. Some are well known on account of their hard and black-coloured heart-wood, e.g. Maba ebenus (the Moluccas) and Diospyros ebenum (Ebony-wood, from Tropical Asia) and others.—The fruits are edible e.g. of Diospyros lotus (Date-plum, Asia), which is also cultivated as an ornamental shrub, together with several other species.
Order 3. Styracaceæ. The flower is more or less epigynous, and the corolla is almost polypetalous. The stamens (by splitting?) are more than double the number of the petals, and often united at the base. Stellate hairs are frequent.—235 species; Tropical Asia and America, a few for example in the East.—Officinal: Gum-benzoin from Styrax benzoin and perhaps other species (Sumatra and Siam). Halesia tetraptera (N. Am.) is an ornamental shrub with 4-winged fruits.
Fig. 547.—Diagram of Primula.
Family 28. Primulinæ.
The flowers are regular, ☿, hypogynous, and gamopetalous. The stamens are equal in number to the petals (Fig. 547) and are placed opposite to them. The ovary is unilocular, with a free, central placenta with 1–many ovules.—The flower is a further development of the Diospyrinæ; the suppression of the calyx-stamens, which commenced in this family, is carried further in the Primulinæ, so that in the majority of cases no trace of them is present, but in certain species and genera (Samolus, Lysimachia thyrsiflora, Soldanella, certain Myrsineæ) some small bodies (scales, teeth, etc.) are found in the position of the suppressed stamens. Again, the lateral portions of the carpels are suppressed, so that the ventral placentæ with the ovules are separated from the dorsal portions, and are united into a free central placenta; this theory is supported by the branching of the vascular bundles, the development, and various comparative considerations.—Sn, Pn, A0 + n, Gn; where n = 4–8, generally 5. The carpels are placed opposite the sepals (Fig. 547).
Order 1. Primulaceæ (Primroses). This order has many ovules attached to a thick, free, central placenta (Fig. 547); style undivided with a capitate stigma; ovules semi-anatropous; fruit a capsule with many seeds.
All the plants belonging to this order are herbs; stipules wanting; the flower is most frequently 5-merous (S5, P5, A0 + 5, G5; except Centunculus and Trientalis). The corolla and capsule have various forms, but the capsule generally opens by teeth at the apex. The ovules are semi-anatropous (in Hottonia they are anatropous), and the seeds are therefore peltate, with the hilum situated in the centre of one side. The endosperm is fleshy or horny. The flowers are borne either in racemes or in umbels; as bracteoles are typically absent (Fig. 547), cymose branching does not occur.
Fig. 548.—Primula: dimorphic flowers. A short-styled; B long-styled.
Fig. 549.—Cyclamen persicum.
Primula (Primrose) has most frequently a vertical rhizome, bearing a rosette of leaves at its summit, and long-stalked umbels; corolla rotate or slightly funnel-shaped; the capsule opens at the apex by 5 teeth. The flowers in some species are heterostyled (long-styled or short-styled; Fig. 548). Closely allied are Androsace (with ovate, cup-shaped corolla-tube and ligular scales, alternating with the corolla-lobes) and Soldanella (funnel-shaped corolla with laciniate lobes and most frequently ligular scales).—Hottonia (Water-Violet) is an aquatic plant with pectinate leaves and heterostyled flowers.—Cortusa. Dodecatheon. Cyclamen (Fig. 549) has solitary, long-stalked flowers, and a rotate corolla with the lobes reflexed; the stalk of the capsule rolls up spirally; the tuberous rhizome is formed by the hypocotyledonary internode. Only 1 cotyledon.—Lysimachia (Money-wort); stem-internodes well developed, leaves opposite or verticillate, calyx almost polysepalous, corolla deeply 5-partite (Fig. 550). The flowers are solitary or in racemes.—Anagallis (Pimpernel), leaves opposite, flowers solitary; the fruit a pyxidium (Fig. 551); similarly in Centunculus, which is 4-merous.—Trientalis, the flowers are most frequently 7-merous.—Glaux (Sea Milk-wort) is a creeping maritime plant with opposite leaves; flowers solitary in the leaf-axils, corolla absent, but with coloured calyx. The petals are usually developed later than the stamens in the Primulaceæ; but in this instance they are entirely suppressed.—Samolus (Brookweed) differs from all the others in having an epigynous flower; barren sepal-stamens are also present. The bracts in the racemose inflorescences are displaced along the flower-stalks.
Fig. 550.—Lysimachia thyrsiflora.
Fig. 551.—Anagallis arvensis. Fruit dehiscing.
Pollination. Insect-pollination in the majority; cross-pollination is promoted in some by heterostyly (Fig. 548).—300 species; especially in northern temperate zones; the majority on mountains (Soldanella, Androsace, etc.); almost absent in the Tropics. A large number are ORNAMENTAL PLANTS, e.g. Primula auricula (from the Alps), P. sinensis (China), P. elatior (Oxslip, a native) and grandiflora, etc. Cyclamen europæum (Alpine Violet); the tubers are poisonous.
Order 2. Myrsinaceæ. Trees or shrubs; evergreen, tropical Primulaceæ with fleshy fruits and few seeds, embedded in the placenta. The leaves are nearly always dotted with yellow glands (schizogenous resin-receptacles).—550 species; especially Am.—Ornamental plants: Ardisia crenulata (W. Ind.); other genera: Clavija, Maesa, Theophrasta (barren sepal-stamens), Myrsine, Jacquinia (barren sepal-stamens), etc.—Ægiceras, allied to this order, comprises arborescent plants, often growing with Rhizophora in tropical forests, along the shore. The embryo germinates while still in the fruit.
Order 3. Plumbaginaceæ. This order has a position of the stamens similar to that in Primulaceæ (S5, P5, A0 + 5, G5), but it differs from these in the flower, which has generally a membranous, dry, thin, coloured, folded, almost entire calyx and an almost entirely polypetalous corolla, which, as a rule, has twisted æstivation and is only united with the stamens at its base; but more especially it differs in the ovary, which bears 5 free or almost free styles and only 1 basal ovule with a long, twisted funicle (the placenta of the Primulaceæ is here so much reduced that it bears only 1 ovule). The fruit is a nut or capsule. The radicle is turned outwards. Endosperm mealy.—To this order belong herbs or under-shrubs, which are especially natives of the sea-coast and of salt-steppes; they also resemble the Primulaceæ in the scattered, undivided, entire leaves (without stipules), often in rosettes, and the inflorescence borne on a long stalk. In opposition to the Primulaceæ, the bracteoles are typically present, and hence the branching is generally cymose (scorpioid).
Armeria (Thrift) has a round capitulum, composed of closely-packed dichasia, surrounded at its base by an involucre with peculiar prolongations, directed downwards, and united into a sheath protecting the intercalary zone of growth. The pericarp is finally ruptured at the base, and drops off like a hood.—In Statice (Sea-lavender), the unipared scorpioid cymes are prolonged and collected into panicle-like inflorescences.—Plumbago is the genus which approaches nearest to the Primulaceæ, and differs most from the characters given above. It has capitate or spike-like inflorescences, a salver-shaped corolla, and the stamens are not attached to the corolla. The style is only divided at the extremity; the calyx is not membranous, but is covered with sticky, glandular hairs.
250 species; chiefly in the Mediterranean and about the Caspian Sea, on salt-steppes and beaches. Some are Tropical; a few are ornamental plants.
B. Tetracyclicæ.
a. Tetracyclicæ with hypogynous flowers.
Family 29. Tubifloræ.
The flower is regular, ☿, and hypogynous. The gamopetalous type is present in this family with great uniformity, without suppression or splitting; S5, P5, A5, G2 (3–5). The stamens are all fertile, alternating with the lobes of the corolla. Gynœceum with 2, more seldom 3–5 syncarpous carpels. Style nearly always simple; 2 dorsal stigmas. In each carpel 2–∞ ovules. At the base of the ovary is found a yellowish ring-like nectary (Fig. 552 C), sometimes 5-sinuate or 5-partite.—The leaves are nearly always scattered; stipules are absent.—The Solanaceæ, which formerly were classed here, are so closely allied to the Personatæ, that it would be unnatural not to place them first in this family; and the Boraginaceæ (which were also placed in the Tubifloræ) appear to be best united, with the Labiatæ and others, into one family Nuculiferæ.
Order 1. Polemoniaceæ. The flowers are regular; S5, P5, A5, G3. The calyx and corolla have united leaves, the petals twisted to the right in æstivation (all the left edges being covered). The ovary is 3-locular with 2–∞ ovules in each loculus; the style is trifid at the apex; the fruit is a 3-valved capsule. Embryo straight; endosperm fleshy. The inflorescences are dichasia passing over into unipared helicoid cymes (the shoot of the lower bracteole being the more strongly developed).—Herbs without latex. 150 species; especially Western N. Am.—Phlox (salver-shaped corolla; entire, opposite leaves), Polemonium (campanulate or almost rotate corolla; scattered, pinnate leaves), Leptosiphon, Gilia, Collomia, Cobæa (climbing, like the Vetches, by tendrils at the ends of the leaves), etc. They are frequently ornamental plants.
Order 2. Hydrophyllaceæ. This order approaches very closely to the Boraginaceæ. Herbs with pinnate or palmate leaves; S5, P5, A5, G2. The lobes of the corolla are imbricate in æstivation. Generally 2 median carpels. The ovary is most frequently unilocular, and the seeds are situated on 2 parietal placentæ; capsule 2-valved; embryo straight; endosperm fleshy. In the corolla-tube, opposite the corolla-lobes, there are frequently appendages of various forms, which resemble those of Cuscuta. The inflorescences correspond exactly with those of the Boraginaceæ, being unipared scorpioid cymes, which, prior to opening, are tightly rolled up.—130 species, especially in N. Am. (California, etc.). Many annual species of Phacelia, Nemophila, Whitlavia, Eutoca, Cosmanthus, etc., are cultivated in gardens as ornamental plants. Hydrolea (has a bilocular ovary, and two free styles).
Order 3. Convolvulaceæ (Bindweeds). The flower is regular, hypogynous, with 5 almost free sepals (quincuncial æstivation), P5, A5, G2 (rarely 3–5). The corolla is very characteristic; it is (with various forms) almost entire, or slightly 5-lobed, and folded longitudinally in the bud in such a way that 5 projecting, flat portions, tapering towards the top and frequently differing in colour and hairiness from the rest, are visible externally and applied close together, while the remainder of the corolla is folded inwards (Fig. 552 A); and hence the whole corolla is strongly twisted to the right in the bud. The gynœceum most frequently has a bilocular ovary; in each loculus there are only 2 (erect) anatropous ovules on the placenta, which is not especially thickened (Fig. 552 D, E); each loculus is sometimes divided into two by a false septum (a relationship with the Boraginaceæ, etc.); style simple with most frequently a bilobed stigma, or a bipartite style. The fruit is nearly spherical, most frequently a capsule. The seeds are erect, and have a large hilum at the base. The embryo is curved, with leaf-like, thin, bilobed, most frequently folded cotyledons; endosperm absent or mucilaginous.
1. Convolvuleæ, Bindweed Group. The majority are twining (to the left) herbs, with latex. The leaves are scattered, without stipules, often long stalked, and nearly always with cordate base; some are palmately lobed. The flowers are most frequently solitary in the leaf-axils, large, quickly withering.—Convolvulus (Fig. 552), Calystegia (unilocular ovary, 2 large bracteoles), Ipomœa, Batatas, Evolvulus (with a doubly bifid style), Calonyction, Pharbitis, etc.
Fig. 552.—Convolvulus scammonia.
2. Dichondreæ. This group is a more primitive form, not twining, and without latex. It has 2 free carpels with basal style (as in Boraginaceæ) and valvate corolla.
3. Cuscuteæ, Dodder Group (Fig. 553). Parasites, with round, filamentous stems, bearing only scale-like leaves and almost destitute of chlorophyll (they are reddish or yellowish); they are parasitic upon other plants, around which they twine, first with narrow, compact coils from which haustoria (Fig. 553 A) are developed which enter the host-plant, and then with wider coils by which they raise themselves to other portions of their host or try to reach other plants. On germination a very temporary primary root is developed, which bears root-hairs as far as the tip (rootcap is wanting); it only serves as a kind of reservoir for water, and perishes very soon after the seedling has fastened on to a host. The embryo is filamentous and rolled up spirally (Fig. 553 C), and is sometimes destitute of cotyledons. The flowers are crowded into capitulate inflorescences, complicated by accessory shoots (Fig. 553 A); they have S5, P5 (imbricate æstivation), A5 (and beneath the stamens 5 scales on the corolla-tube), G2. Fruit a capsule opening by a lid.—Cuscuta europœa, C. epilinum (Flax-Dodder), C. epithymum (Lesser-Dodder), C. trifolii (Clover-Dodder), etc., are parasitic on different hosts, or parasitic each on its own particular host.