Mrs. Loudon

THE ORDER ERICACEÆ: ILLUSTRATED BY THE COMMON OR BESOM HEATH, THE MOOR HEATH, CAPE HEATHS, LING OR HEATHER, ANDROMEDA, LYONIA, ST. DABÆOC’S HEATH, ARBUTUS, THE BEARBERRY, GAULTHERIA, CLETHRA, RHODODENDRON, INDIAN OR CHINESE AZALEAS, YELLOW AZALEA, AMERICAN AZALEAS, RHODORAK, ALMIA, MENZIESIA, LOISELEURIA, LEDUM, LEIOPHYLLUM, THE BILBERRY, THE WHORTLE-BERRY, THE CRANBERRY, PYROLA, AND MONOTROPA.

The name of EricaceÆ, which most people are aware signifies the Heath family, conjures up immediately the image of a number of narrow-leaved plants, with globular, ventricose, or bell-shaped flowers; and we are apt at first to think that the family is so natural a one, as to require very little explanation. Did the order include only the Heaths, this would be the case, for all the Heaths, different as they are in some particulars, may be recognised at a glance: but as the order includes the Rhododendrons, Azaleas, and Kalmias, besides several other plants which have not so strong a family likeness to each other as the Heaths, it becomes necessary to say a few words on the botanical resemblances which connect them together. The first, and most striking, of these is the shape of the anthers, each of which appears like two anthers stuck together, and the manner of their opening, which is always by a pore or round hole, in the upper extremity of each cell. The filaments, also, in all the genera, except Vaccinum and Oxycoccus, grow from beneath the seed-vessel, being generally slightly attached to the base of the corolla. There is always a single style with an undivided stigma, though the capsule has generally four cells, each containing several of the seeds, which are small and numerous. The calyx is four or five cleft, and the corolla is tubular, with a larger or smaller limb, which is also four or five cleft. The order has been divided into four tribes, which I shall describe in this chapter, though some of these are considered as separate orders by Dr. Lindley and other botanists.

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TRIBE I.—ERICEÆ.

Fig.47.—The Besom Heath (Erica Tetralix). This tribe, which comprehends all the heath-like plants, has been re-divided into two sub-tribes, one containing the genera most nearly allied to the heaths, and the other those be longing to the Andromeda. In both there is a honey-bearing disk under the ovary, and the leaves are generally rolled in at the margin, as shown at a, in fig. 47.

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SUB-TRIBE I.—ERICEÆ NORMALES.

All the genera in this sub-tribe, twenty-two in number, were formerly included in the genus Erica; and some botanists still consider all the species to belong to that genus, with the exception of those included in Calluna, while others adopt about half the new genera. In this uncertainty, I shall only describe two of the doubtful genera, partly because the distinctions between them and the true heaths are strongly marked, and partly because the species they contain are frequently met with in British gardens and greenhouses, where they are sometimes labelled with their old names and sometimes with their new ones.

In the genus Erica, one of the commonest species is the Besom Heath (E. tetralix), which is found in great abundance on moorish or boggy ground in every part of Britain. In this plant, the corollas of the flowers appear each to consist of a single petal, forming an egg-shaped tube (see b in fig. 47), contracted at the mouth, but afterwards spreading into a four-cleft limb, through which is seen projecting the style, with its flat stigma. The corolla is, however, really in four petals, which, though they adhere together, may be easily separated with a pin. The stamens are concealed by the corolla, but the manner in which they grow is shown at c; and d is a single stamen, showing the spurs or awns at the base of the anther, the position of which is one of the characteristics of the genus Erica in its present restricted form; e is a capsule with the style and stigma attached; and a is a leaf showing its revolute or curled back margin. The leaves of this species are in whorls, four leaves in each whorl, and they are ciliated, that is, bordered with a fringe of fine hairs.

All the true Heaths bear more or less resemblance to this plant. In some, the corollas are bell-shaped, spreading out at the tip into five teeth, which inclose the stamens, as shown in fig. 48; and in others they are nearly globose swelling out near the calyx, and tapering to a Fig.48.—Bell-shaped Heath. Fig.49.—Cape Heath.
(E. hispida.) point, beyond which the stigma and anthers project; as in the Cape Heath, called Erica hispida, a flower of which is shown in fig. 49. The leaves also differ exceedingly, in the number contained in each whorl; as in some species there are only three in a whorl, while in others they are five or six. The general features of all the Heaths are, however, the same—viz., there are eight stamens, which are generally inclosed in the corolla, though they sometimes project beyond it, as shown in fig. 49, and the anthers of which are two-cleft, and awned or crested at the base, while the filaments are hair-like; one style, which always projects beyond the corolla, and has a flattened stigma; a four-parted calyx and corolla which is tubular, with a four-parted limb. There are nearly two hundred species of this genus, some of which are natives of Europe, and others of the Cape of Good Hope.

The moor Heaths (Gypsocallis) were separated from the genus Erica, by Mr. Salisbury, principally on account of the corolla being campanulate, or shortly tubular, with a dilated mouth; and the stamens projecting beyond the corolla. The filaments are also generally flat; the anthers are without awns, and distinctly in two parts; and the stigma is simple, and scarcely to be distinguished from the style. The common Cornish Heath (G. vagans), and the Mediterranean Heath (G. Mediterranea), are examples of this genus, which appears strongly marked, though, as I before mentioned, some botanists do not adopt it.

Callista is a genus established by the late Professor Don, which appears very distinct, Fig.50.—Callista bucciniflora. though it also has not been generally adopted. It includes all those beautiful Cape Heaths which have a shining, glutinous, ventricose, or cylindrical corolla with a spreading limb (see a in fig. 50), and a capitate stigma (b). C. bucciniflora and C. ventricosa, are examples of this genus.

The Ling or Heather, which LinnÆus called Erica vulgaris, is now generally placed by all botanists in a separate genus called Calluna, which was established by Mr. Salisbury. The calyx of this plant is membranous, and coloured so as to Fig.51.—Stamen of the Ling. resemble a corolla, and it is furnished with four bracts at the base, which resemble a calyx. The true corolla is bell-shaped, and shorter than the calyx. The stamens are inclosed, and the anthers are of the very singular form shown in fig. 51. The stigma is capitate, and the flowers are disposed in what is called a racemose spike. The leaves are trigonal; they are very short, and they are laid over each other like scales in four rows. The Ling is the only species in the genus.

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SUB-TRIBE II.—ANDROMEDEÆ.

The plants in this sub-tribe differ decidedly from those of the preceding division, in having ten stamens, while all the genera of heaths have only eight. The calyx is also five-cleft instead of four; and the corolla, which falls before the seeds are ripe, has a five-lobed limb. The sub-tribe is divided into twenty genera, more than half of which are perfectly distinct.

The genus Andromeda is distinguished by its globose corolla which has a five-lobed limb; and its stamens which have their filaments bearded, and their anthers short and two-awned. Fig.52.—Stamen of Andromeda. Fig. 52 shows a stamen of the wild rosemary (Andromeda polifolia) with its bearded filament (a), and its two-awned anther with its pore-like openings (b). The cells of the capsule open in the middle, down the back, to discharge the seeds. Professor Don has divided the genus Andromeda into six genera; some of which contain only one or two species. Thus only Andromeda polifolia and A. rosmarinifolia are left in the genus Andromeda; Cassandra contains only A. calyculata, and A. angustifolia; and Zenobia, only the beautiful Andromeda speciosa. In Cassandra the anthers Fig.53.—Leaf and anther of Cassandra. are long and mutic (see a in fig. 53), and the leaves (b) are without veins, and white and full of dots on the underside, the edges being curled inwards; and in Zenobia the corolla is bell-shaped, with the limb, which is in five lobes, curling back (see a fig. 54). The stamens have the filaments (b) curiously dilated at the base; and the point of each cell of the anther is cut into two erect awns (c). The manner in which the stamens are arranged inside the corolla is shown at (d). The cells of the capsule, when ripe, open down the centre, and the seeds which are angular, are attached to a five-lobed placenta.

Fig.54.—Flowers, corolla, and stamen of Zenobia.

Lyonia is a genus established by the American botanist Nuttall, because the plants it contains have the margins of the valves of their capsules closed by five other narrow external valves. The plants are natives of North America, and their flowers are generally small. Lyonia Mariana may serve as an example of this genus, which is generally adopted by botanists.

It would be useless to enter into details of the other genera formed out of Andromeda, as they are not generally adopted; but, perhaps, it may be worth mentioning, that the well-known Andromeda floribunda is placed by Professor Don in a new genus which he calls Leucothoe.

St. Dabeoc’s Heath, or Irish Whorts, a little heath-like shrub, common in Ireland, is one of those plants which have puzzled botanists exceedingly. It has been called successively Erica, Andromeda, and Menziesia, Daboecia; then Erica Hibernica, next Menziesia polifolia, then Vaccinium Cantabrieum and lastly Daboecia polifolia. It is probable, however, that it may even yet be doomed to undergo other changes; as, from the construction of its anthers, which are linear, and arrow-shaped at the base, and which open lengthways, instead of by pores, it does not appear even to belong to the EricaceÆ.

The other genera in this sub-tribe are quite distinct from each other, and contain several well-known plants. The most popular of these genera are Arbutus, Arctostaphylos, Gaultheria, and Clethra.

The Strawberry tree (Arbutus Unedo) has little bell-shaped flowers, contracted at the mouth, and with a curling-back limb, which are easily recognised as belonging to the EricaceÆ. They have ten stamens, the filaments of which are hairy at the base (see a in fig. 55) and Fig.55.—Fruit &c. of Arbutus Unedo. inserted in the disk; which in this genus is large, and rises up round the ovary (see b). The calyx is permanent, and five-cleft; and the flowers are produced in panicles, and each is furnished with a bract. The fruit, which retains the calyx when ripe, is a granular berry, covered with tubercles on the outside; and it has five cells (c) containing the seeds. There are numerous varieties of this species common in British gardens, besides a very beautiful hybrid between it and A. Andrachne. The latter species is a native of Greece, and rather more tender than the common kind; and it is very conspicuous in shrubberies from its red stems and loose bark.

The Bearberry (Arctostaphylos Uva-Ursi) was formerly considered to belong to the genus Arbutus, but it differs in the filaments of the stamens being smooth and dilated at the base, and the awns affixed to the middle of the anthers. The berry is without tubercles, and the cells are often only one-seeded.

There are two species of Gaultheria common in British gardens: viz.—G. procumbens and G. Shallon: both of which have flowers resembling those of the Arbutus and furnished with bracts; but in the former species the flowers are solitary and produced from the axils of the leaves, and in the latter they are in racemes, of the kind called secund, that is with the flowers growing all on one side. The berries of both kinds are eatable, and those of G. procumbens are called Partridge berries in America, and the leaves Mountain tea. Both species have ten stamens, the anthers of which are two-cleft, each cell being furnished with two horns, as in Zenobia speciosa (see fig. 54, in page 116). The fruit is five-celled and the seeds are numerous.

The genus Clethra differs considerably from the preceding genera, as the limb of the corolla Fig.56.—Flower of Clethra Alnifolia. is so large and so deeply cleft, as to make the flower appear to have five petals (see a in fig. 56). There are ten stamens, with broad arrow-shaped anthers (b), and a three-cleft stigma, (c). The capsule is dry, with three many-seeded cells. In C. alnifolia, a native of North America, (of which fig. 56 represents a magnified flower,) the flowers are erect, and produced in a spicate raceme; but in C. arborea, a native of Madeira, the racemes are panicled, and the flowers drooping and somewhat bell-shaped. Both species are very ornamental.

TRIBE II.—RHODOREÆ.

The plants included in this tribe are all considered to bear more or less resemblance to the Rhododendron, though in some of them the family likeness is not very strong; and the genera I shall describe to illustrate it are Rhododendron, Azalea, and Rhodora (the last two being by some botanists included in Rhododendron); Kalmia, Menziesia, and Ledum.

The species of the genus Rhododendron are easily distinguished by their flower buds, which are disposed in the form of a strobile, or pine-cone, each bud having its accompanying bract, which the flower retains after its expansion, as shown in fig. 57 at a, in a flower of R. maximum. There are five or ten stamens of unequal length, the larger ones curling upwards (as shown at b in fig. 58), as does the style (c), which has a simple stigma. The flowers have a very small calyx, (d in fig. 57,) and a campanulate corolla which is deeply five-cleft, the upper segment (e in fig. 58) being somewhat larger than the rest, and spotted in the inside. The capsule is five-celled and five-valved, as shown in fig. 57 f. The leaves of nearly all the species are evergreen; and the flowers are showy, and produced in terminal corymbs. The principal species may be thus distinguished from each other; R. maximum has drooping leaves, covered with brown or white down on the under surface, and a dense corymb of flowers, the segments of the corollas of which are roundish, and the bracts leafy. In R. ponticum, on the contrary, the corymbs of flowers are looser, the segments Fig.59.—Seed-pod of Rhododendron Ponticum. more pointed, and the bracts more scale-like; and the leaves are smooth on both surfaces. The seed-pods also differ: in those of R. maximum and the other American species, the valves are smooth as shown at f in fig. 57; and in those of R. ponticum, the valves are somewhat crinkled as shown in fig. 59. This species, and all its hybrids and varieties, are more tender than R. maximum, R. catawbiense, and all the other American kinds and their offspring. R. catawbiense has the flower of a darker colour on the outside of the corolla than within, and the upper segment is very faintly dotted. It hybridises freely with R. arboreum, which R. maximum does not, and the hybrids thus produced are hardier than those raised from R. ponticum, though the latter are by far the most numerous.

Most of the species have purple or whitish flowers, but some, such as R. chrysanthemum, and R. anthopogon, have yellow flowers; R. ferrugineum and R. hirsutum, have bright pink or rose-coloured flowers; and those of R. arboreum the Nepaul tree Rhododendron, are of a rich scarlet. The commonest small kinds are R. ferrugineum and R. hirsutum, both dwarf shrubs and natives of the north of Europe, with funnel-shaped corollas, and leaves dotted on the under surface. They are so much alike as scarcely to be distinguished at first sight, but on examination the leaves of R. ferrugineum will be found to have brown dots, and to be plain on the margin; while those of R. hirsutum have white dots and are fringed with fine hairs.

Of all the species of the genus, those which differ most widely from the others are the Indian kinds. Of these R. arboreum has a ten-celled capsule, and the segments of the corolla two-lobed with waved margins. The leaves are long and silvery beneath; and the capsules, the peduncles, and the calyxes, are all woolly. In R. campanulatum, a splendid species with very large flowers, the capsule is six-celled, the leaves are somewhat cordate at the base, and the bracts are fringed; and in R. anthopogon the corolla has a cylindrical tube, woolly inside, and a small but spreading limb, cut into five lobes. There are eight stamens, and the capsule is five-celled.

R. Camtschaticum, R. ChamÆcistus, and R. dauricum differ from the preceding species in having their corollas rotate, that is, wheel-shaped. The last of these kinds is a favourite greenhouse shrub, from its flowering under shelter in winter. In the open ground it flowers in March. The species has rose-coloured flowers which appear before the leaves; and leaves which turn red in autumn before they fall. The roots are knobbed and fibrous; and the stems are twisted and knobbed in a wild state. There is a variety R. d. atrovirens which has purple flowers, and evergreen leaves, and which is hardier than the species.

The genus Azalea may be divided into three kinds, viz., A. indica and its allied species; A. pontica and its varieties and hybrids; and the American Azaleas. These divisions are easily distinguished by their flowers. Those of the Indian or Chinese Azaleas have all large showy flowers, on short downy footstalks, and they are produced in small clusters of only two or three flowers each, at the extremity of the shoots. The corollas are bell-shaped and deeply cut, nearly to the base, into broad spreading segments. The stamens are ten in number, shorter than the corolla, and of unequal length. The leaves are evergreen, and they are numerous, thickly set and downy. These Azaleas are all very handsome, but the white Indian Azalea (A. indica alba, or A. ledifolia) is particularly so, and very fragrant. The species belonging to this division are mostly natives of China, and require either a greenhouse or some slight protection during winter in England.

The yellow Azalea (A. pontica or Rhododendron flavum) differs from A. indica in being quite hardy; in the flowers being produced in umbels of from eight to twelve, at the ends of the branches, before the leaves; and in the corollas being funnel-shaped instead of campanulate. The tube of the funnel is, however, shorter than the limb, the segments of which are broad and spreading, the upper three being larger and of a darker yellow than the two below. There are usually five stamens, projecting a little beyond the corolla, and curving upwards; the style also curves upwards, and it is crowned by the stigma, which forms a round green head.

The calyx is very small, and both it and the corolla feel clammy to the touch. The flowers are fragrant. The leaves are deciduous, and they are ovate, slightly hairy, and terminate in a mucro or stiff point. There are many varieties of this species, and many hybrids between it and the American kinds, all of which are quite hardy in British gardens.

The principal American Azaleas are A. nudiflora, A. viscosa, A. nitida, and A. speciosa, all of which have the corollas of their flowers funnel-shaped. Of these A. nudiflora is easily known by its stamens, which project a long way beyond the corolla, and by the tube of the corolla being longer than the limb. The plant is deciduous; and the flowers, which are produced in large terminal clusters, and which are not clammy, appear before the leaves. The common English name for this plant in some parts of the country is the American Honeysuckle, and the flowers are of various shades of red, pink, white, and purple. A. calendulacea, which some botanists make a variety of this species, has much larger flowers, and the leaves pubescent on both surfaces, whereas, in A. nudiflora the leaves are nearly smooth and green, with only a slight fringe of hairs round the margin. There are numerous varieties of A. calendulacea, the flowers of which are always either yellow, red, orange, or copper-coloured, and it is supposed to be the parent of the beautiful Ghent Azaleas. A. viscosa has the tube of the corolla equal in length to the limb, and rather short stamens; the flowers of this species are clammy. A. hispidum, which is generally considered a variety of A. viscosa, is still more clammy, and the tube of the corolla is wider and shorter; other probable varieties are A. nitida, which has shining leaves, and A. glauca, which has glaucous ones, as in both kinds the flowers are very clammy. A. speciosa has large flowers and leaves tapering at both ends. All the species of Azalea have five stamens, but some of the varieties have ten.

Rhodora canadensis is a little American shrub with pink flowers, which appear before the leaves, and the corolla of which is bilabiate, the upper lip being the broadest, and cut into two or three teeth, and the lower only once cut. There are ten stamens, and the capsule is five-celled and five-valved. The leaves are deciduous, and slightly pubescent beneath; and the flowers are produced in small terminal clusters. This plant, as well as all the Azaleas above described, are now included by some botanists in the genus Rhododendron.

The genus Kalmia also belongs to this tribe. The flowers of this well known shrub are very curiously constructed. The corolla is salver-shaped, that is, nearly flat, and on the under side of the limb are ten protuberances, producing as many hollows on the upper side, in which lie half-buried the ten stamens. This singular construction gives the corolla that wrinkled appearance which has procured for the plant its American name of Calico flower; while, from the shape of the leaves, it is also frequently called the Mountain laurel; it is also called Sheep laurel from its being considered poisonous to those animals when they feed on it. There are several species, which differ from each other principally in the shape of their leaves and the size of their flowers.

Menziesia is a genus containing only three species, of which M. pilosa (fig. 60) may be taken as an example. The flowers are small and bell-shaped, and the anthers (a) are without any awns or bristles; there are eight stamens, and the curious manner in which they are crowded round the style is shown at b. The capsule is four-celled.

Loiseleuria, or Azalea procumbens, is a small plant, having the appearance of thyme, which is the only species left in the genus Azalea by those botanists who include the true Azaleas in the genus Rhododendron.

Ledum is the last genus belonging to this tribe that I shall attempt to describe. Ledum palustre, or wild Rosemary, the best-known species, has a corolla in five regular petals, and ten stamens which project beyond it; but L. latifolium, the Labrador Tea, has only five stamens, which are not longer than the petals. L. buxifolium, a little thyme-like shrub, is now called Leiophyllum thymifolium. All the species have white flowers.

TRIBE III.—VACCINIEÆ.

Fig.61.—Common Bilberry (Vaccinium tenellum).The plants comprised in this tribe, which is considered a separate order by many botanists, all agree with the genus Vaccinium in having the ovary entirely surrounded by the calyx, which forms a fleshy berry-like fruit when ripe, and in the seeds being scaly. Vaccinium Myrtillus, the common Bilberry or Blaeberry, is a familiar example of the genus; and fig. 61 shows the shape of the flowers at a, the manner in which the ovary is enveloped in the calyx at b, and the curious shape of the anthers in the magnified representation of them at c. The berry is five-celled and many-seeded; and there are eight or ten stamens. Both the anthers and the flower vary in the different species, but the calyx and the manner in which it surrounds the ovary are nearly the same in all, as may be seen in fig. 62, which represents a specimen of V. tenellum, the Pennsylvanian Whortle-berry. In this figure a is the flower, b the anther, and c the ovary surrounded by the calyx.

There are many species, among which may be mentioned the American Bluets (V. angustifolium); Deerberries (V. stamineum); Bluetangles (V. frondosum); the Hungarian Whortle-berry Fig.63.—Cranberry. (V. Arctostaphylos); and the Cow-berry, or common British Whortle-berry (V. Vitis-IdÆa).

The Cranberry (Oxycoccus palustris) differs from the genus Vaccinium in the shape of its flowers (see fig. 63), and in its anthers being without spurs; there are eight stamens, the filaments of which are connivent, that is, growing close together. The American Cranberry (O. macrocarpus) differs from the European kind, principally in having larger fruit.

TRIBE IV.—PYROLEÆ.

This tribe is also considered as a separate order by many botanists; but the principal distinction is the long arillus or skin which enfolds the seeds and gives them the appearance of being winged. The most remarkable genera are Pyrola, the Winter Green, of which there are several species common in moist woods in the north of England and Scotland; and Monotropa, or Bird’s-nest, parasitic plants which grow on the roots of pine and beech-trees, but are by no means common in England. The species of Pyrola are pretty little evergreen plants, with white flowers, the corollas consisting of five distinct petals, and which have ten stamens, the anthers of which are two-celled, each opening by a pore; the style is single, ending in a capitate stigma cut into five lobes; and the capsule is five-celled. The yellow Bird’s-nest, (Monotropa Hypopitys) has a coloured stem, with drooping flowers, and numerous scales instead of leaves, of which it is destitute. The flowers have a coloured calyx cut into four or five segments, and the corolla is in four or five petals. There is an American species with white flowers.