Part 47

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._~

_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_.

=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_.

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.

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.