XIXBY THE RIVER SIDE

The Salad Burnet.

In similar situations we may find the Lesser Burnet or Salad Burnet (Poterium Sanguisorba) of the same order. This plant is so different in general appearance from the majority of the Rose family that the amateur would hardly associate it with the others. The flowers are small, and collected together in dense, purple cymes on the top of long, angular stalks. They have no petals, and the four overlapping sepals are usually deciduous. The stamens, five to thirty in number, are pendulous on long, slender filaments; and the upper flowers display their crimson stigmas before the lower ones produce their stamens. The stem is erect, from six to eighteen inches in height; and the pinnate leaves have many small, sessile, oblong leaflets with coarsely-serrate edges. This plant flowers during June, July, and August.

The Field Gentian.

The Bedstraw Family (orderRubiaceæ) is represented on the chalk by the Rough-fruited Corn Bedstraw (Galium tricorne), which is common in fields. It is a spreading plant, with procumbent stems, one to three feet long; and small, long, narrow leaves, rough with recurved prickles, arranged in whorls of from six to eight. The flowers are small and white, grouped in little cymes of three. The fruit is comparatively large, and granulated, but not bristly, and it droops by the bending of the pedicel. The plant flowers from June to October.

The Red Spur Valerian (Centranthus ruber—orderValerianaceæ) is a glaucous, leafy plant (seePlate VIII), sometimes growing to a height of two feet or more, often to be seen in chalk-pits and limestone quarries, and frequently on old walls. It is not indigenous, but is cultivated largely as a garden flower, and has now become naturalised. Its corolla, which is sometimes white, has five unequallobes, a long, flattened tube, and a slender spur. The plant flowers from June to September.

Of the Composite flowers we shall note two species, the first being the Woolly-headed Plume-thistle (Carduus eriophorus), common in chalky fields, where it throws up its large, cottony heads to a height of from three to five feet during July and August. In order to distinguish it from other similar thistles we must note that its stem is not winged, and that the deeply-divided leaves, with bifid lobes, half clasp the stem at the base; also that the involucre bracts are lanceolate, with long, reflexed spines. The heads of this thistle are of a pale purple colour, of a globular form, two to three inches in diameter, and covered with a thick, cottony growth.

The Yellow-Wort.

Our other example of the Composite flowers is the Ploughman's Spikenard (Inula Conyza), which is common on chalky banks and pastures, flowering from July to September. It is an erect, downy plant, from two to five feet high, with oval, lanceolate, downy leaves of a dull green colour. The upper leaves are entire and sessile, while the lower are toothed and stalked. The numerous flowerheads are of a dull yellow colour, with leaflike bracts, arranged in a branched corymb. The involucre bracts are linear and reflexed, and the ray florets are inconspicuous.

Two representatives of the orderGentianaceæare commonly found on chalk hills and pastures; they are the Field Gentian (Gentiana campestris), and the Perfoliate Yellow-wort (Chlora perfoliata, orBlackstonia perfoliata). The former is an erect plant, from four to ten inches high, with a branched stem; opposite, sessile leaves; and conspicuous, bluish-purple flowers, blooming in August and September. The calyx is cleft into four, the two outer segments being large and ovate. The corolla is also four-cleft, and salver-shaped.

The Great Mullein.

The Yellow-wort is an erect, glaucous plant, with an unbranched stem from six to eighteen inches in height, and beautiful yellow flowers, from four to nine in number, arranged in a cyme. The leaves are in widely-separated pairs, united at their bases, so that the stem penetrates them. The calyx is deeply divided, and the limbs of the corolla are spreading. This plant flowers from June to September.

Some species of Mullein (Verbascum) are particularly partial to chalk and limestone districts. They are handsome plants, belonging to the orderScrophulariaceæ, rendered conspicuous by their woolly leaves and spikes of yellow or white flowers. The Great Mullein (V. Thapsus) is common on banks and roadsides, and flowers from June to August. Its stem is stout, erect, very woolly, and varies from two to five feet in height. The leaves are very large and thick, and are so woolly on both sides that they resemble flannel. The flowers form a large, dense, club-shaped spike. Each has a corolla with five spreading lobes; and five stamens, with white hairs on their filaments, two longer than the otherthree. The fruit is a capsule containing many seeds and splitting longitudinally.

The White Mullein (V. Lychnitis) is not at all common, but may be found in similar situations. Its stem is angular, seldom more than three feet high, the leaves nearly smooth above, and the flowers white or cream, blooming from June to August.

A third species—the Yellow Hoary Mullein (V. pulverulentum)—grows on banks, chiefly in Norfolk and Suffolk, flowering during July and August. It is about three feet in height; the stem is round, with a mealy surface; and the leaves, which are not continued down the stem, are covered both above and below with starlike hairs that give them a mealy appearance. The flowers form a pyramidal panicle, and are of a bright yellow colour, with scarlet stamens covered with white hairs.

The Red Hemp-Nettle.

There is yet another species to be found on chalky soils, more especially in hedges and on banks and roadsides. It is the Dark Mullein (V. nigrum), so called on account of the darker hue of the stem and leaves. It grows to a height of about three feet and flowers from June to September. It is a beautiful plant, not so strong in build as the Great Mullein, with an angular stem, and oblong heart-shaped leaves, nearly smooth above, and covered with starlike hairs which give it a downy appearance, especially on the under surface. The leaves are not continued down the stem, and the lower ones have long stalks. The flowers are bright yellow, very numerous, and form a spike-like panicle. The stamens are covered with purple hairs.

The Spiked Speedwell (Veronica spicata), of the same order, neither common nor widely distributed, is to be found chiefly inthe chalk and limestone districts of the South and West of England, flowering during July and August. It has a long, dense, terminal spike of blue or pink flowers about a quarter of an inch in diameter. The corolla has a long tube, and unequal, narrow lobes; and the flattened capsules split into two valves when ripe. A large variety of this species, known as the Tall Spiked Speedwell, occurs in limestone districts of the West. The normal form is shown in Fig. 4, ofPlate VIII.

Of the Labiates perhaps the one most partial to the chalk is the Wild Sage or Clary (Salvia Verbenaca); and even this is not confined to calcareous soils, but thrives in dry pastures in many parts of the country, particularly near the sea. It is an aromatic herb, from one to two feet in height, with long spikes of bluish purple flowers that bloom from May to September. The leaves, which are not numerous, are oblong-cordate (the upper ones broadly cordate), blunt, coarsely toothed, and wrinkled. Other Labiates are very similar to this species, but the Clary may be distinguished by its two ovate, cordate bracts at the base of each flower, and by its narrow corolla, which is a little shorter than the calyx.

The Red Hemp-nettle (Galeopsis Ladanum), of the same order, is common in chalky fields. It is about a foot in height, and displays itsrose-colouredflowers from July to October. The plant is covered with very soft hairs, and the stem is not swollen at the joints. These two features serve to distinguish the species from the Common Hemp-nettle (G. tetrahit) and the Large-flowered Hemp-nettle (G. versicolor) of the same genus. It should also be noted that the corolla is not really red, as the common name suggests, but rose-coloured, while inG. tetrahitit is purple or white, and inG. versicolorit is yellow. The upper lip of the flower, too, is only slightly notched.

The Viper's Bugloss (Echium vulgare—orderBoraginaceæ) is common on dry soils, especially in calcareous districts, where it is often found close to the sea, even on the beach very near high-water level. It is a very peculiar plant, both stem and leaves being thickly covered with stiff, sharp bristles. The stem is unbranched, from two to three feet high; and the leaves are lanceolate. The flowers are of a bright rose-colour when they first open, and afterwards change to a bright purple-blue; they are arranged in short, lateral, curved, one-sided spikes. Both leaves and flowers droop very rapidly after they have been gathered. This plant flowers from June to August.

Another species of the same genus, known as the Purple Viper's Bugloss (E. Plantagineum), is common in the Channel Islands. It may be distinguished by its branched stem and longer spikes of flowers. The lower leaves, too, are oblong and stalked, while the upper ones are cordate and half clasp the stem.

No doubt the reader is already acquainted with the commoner Plantains (orderPlantaginaceæ), so easily distinguished by their spreading radical leaves, with prominent, parallel ribs, and their dense spikes of greenish flowers. There are five British species, one of which—the Hoary Plantain or Lamb's-tongue (Plantago media) is particularly partial to chalky districts, where it grows in pastures and on dry banks. Its flowering stems grow from three inches to a foot in height, and the flowers bloom from June to September. The leaves are elliptical, either sessile or shortly stalked, and have from five to nine ribs. They lie so closely on the soil that nothing can grow beneath them, and even present the appearance of having been pressed against the ground. They also have a downy surface; and the stalk, where it exists, is flattened. The flowering stem is round, and the spike cylindrical. The calyx is cleft into four, with its segments turned backward; and the sepals are not keeled as they are in some other species. The corolla is tubular, with four spreading limbs; and the cream-coloured anthers are displayed on the tips of long filaments.

An Orchis Flower.S, sepals. P, petals. L, lip. C, spur. A, pollen masses. B, stigma.

We have now to consider several representatives of theOrchidaceæ, and it will be well here to note the general characters of this remarkable order as a whole. The Orchids have rounded or palmate tuberous roots, a few glossy leaves which sheath the stem, and simple spikes or racemes of flowers, the prevailing colours of which are red, pink, green and white. The sepals, three in number, often partake more of the nature of petals. There are three petals, the lowest one, forming the lower lip of the flower, often prolonged into a spur, and frequently assuming a remarkable form resembling an insect or some other member of the animal creation. The stamens are united to the style, and form with it a solidcolumn,but usually only one produces pollen, and this one commonly consists of one or two club-shaped masses. The ovary is inferior, often twisted so as to invert the flower, and sometimes so long as to be mistaken for a flower stalk. The stigma is hollow, sticky, and situated just in front of the column above mentioned. The fruit is a three-valved capsule, containing many seeds.

Orchids are generally scented flowers, and produce nectar which is stored either in the cavity of the spur, or within the tissue of the same. In the latter case it cannot be obtained by insects unless they bore into the substance of the spur, and the delay caused renders the removal of the pollen more certain. While the nectar is being withdrawn, the head of the insect is pressed against a sticky disc at the base of the pollen masses, with the result that both disc and pollen masses are bodily removed, and the insect leaves the flower with the whole attached to its head. It often happens, too, that the pollen masses bend forward as the insect flies through the air, and thus they are more likely to be pressed against the stigma when another flower is visited. Here, then, is another wonderful contrivance for the purpose of securing cross-fertilisation, and the whole process may be imitated by thrusting the point of a pencil into the spur of a flower which has not been previously visited by an insect, and then inserting the point into the spur of a second flower. It should be noted, also, that the pollen is not all removed by contact with the sticky surface of a stigma against which the pollen masses are pressed, and thus the pollen obtained from one flower will often fertilise several others.

Our first species—the Broad-leaved Helleborine (Epipactis latifolia), is common in hilly woods, where it flowers during July and August. Its single stem grows from one to three feet high, and the leaves are broadly ovate and ribbed. The flowers are greenish, with reddish-purple lips, and are arranged in a long, loose, one-sided raceme. The sepals are ovate, longer than the acute lower lobe of the lip; and the bracts are generally longer than the flowers. The ovary is downy, and not so long as the bracts. (Plate II, Fig. 5.)

The somewhat similar Large White Helleborine (Cephalanthera grandiflora), which bears creamy white flowers in May and June, is also common in some of the woods on calcareous soils.

The Pyramidal Orchis (O. pyramidalis) grows in limestone pastures, flowering during July and August. This species varies from six to eighteen inches in height, and has linear, acute leaves.The spike of flowers is very dense, of a pyramidal form, and the individual blooms are small, usually of a rose colour, but occasionally white or nearly so. The sepals are spreading, and the lip of the flower has three equal lobes which are oblong and abruptly cut at the tips. The spur is slender and longer than the ovary.

The Fragrant Gymnadenia or Sweet-scented Orchis (Habenaria conopseaorGymnadenia conopsea) is common on chalky heaths and hilly pastures. It grows from twelve to eighteen inches high, has palmate, tuberous roots, and oblong-lanceolate, acute, keeled leaves. The flowers appear from June to August, and are in a dense, elongated spike. The buds are of a deep rose colour, and the open flowers are very fragrant, of a lighter colour, and not spotted. The bracts have three veins; the lateral sepals are spreading; the spur long and slender, much longer than the ovary; and the lip of the flower has three, equal, undivided lobes.

The Sweet-Scented Orchis.

The Green Man Orchis (Aceras anthropophora), though rather rare, and confined to the dry, chalky pastures of East England, is too interesting to be omitted from our selection. The plant is from six to twelve inches high, with palmate tubers, and mostly radical leaves. The flowers are sessile, forming a loose spike, and are strange caricatures of the human figure. Each has a comparatively large green hood, a slender yellowish lip with two lateral lobes to represent the arms, and two similar terminal lobes for the legs. The lateral sepals are green, ovate and convergent; and the flower has no spur. The time of flowering is June and July.

The Green Musk Orchis (Herminium Monorchis), also rather rare, is to be found in chalky pastures of the South, flowering in June and July. It has oval, stalked tubers; two lanceolate, radicalleaves, and generally only one leaf on the slender stem. The spike is loose and slender; and the flowers, which are small and green, are sessile, and emit a musky odour during the night. The sepals are broad ovate; the petals narrower; and the lip is three-lobed, pouch-like at the base, with terminal lobe longer than the other two.

One of the most remarkable, and, at the same time, one of the most beautiful of Orchids is the Bee Orchis (Ophrys apifera). Although not to be described as common, it is frequently to be seen in moderate numbers on banks and in open ground in calcareous districts. Its height is from six to twelve inches, and it flowers during June and July. The leaves are short, oblong, and mostly radical; the bracts large and leafy; and the flowers, numbering from two to six, are arranged in a lax spike, and very closely resemble certain species of bees. The sepals are spreading, oval, and pink inside; and the petals are linear and downy. The lip of the flower is swollen and broad, very velvety, and of a rich brown colour variegated with yellow. It is not longer than the sepals, and has four lobes, the two lower of which are hairy, while the other two are bent under. There is also a sharp, reflexed appendage in the notch. The flower is shown onPlate VIII.

A rare variety, very much like the commoner type just described, is occasionally seen in Kent and Surrey. It is called the Late Spider Orchis (varietyarachnites), and is supposed to resemble a spider more than a bee. The petals are more triangular than in the Bee Orchis, and the lip is longer than the sepals. It may also be distinguished by the appendage in the notch, which is cordate in form, and flat.

Another rare plant—the Spider Orchis (Ophrys aranifera) is to be found in chalky pastures of the South-East. Its flowers are smaller, and generally fewer in number. The sepals are yellowish-green inside, and the petals smooth and linear. The lip is swollen and four-lobed, but without any appendage in the notch, and is of a deep purple-brown, with yellowish markings. This is an earlier species, flowering during April and May.

Our last example of this order is the pretty little Fly Orchis (Ophrys muscifera). It is a slender plant, with a few oblong leaves, and usually from two to ten flowers arranged in a loose spike. The sepals are yellowish-green, and the very slender petals resemble the antennæ of an insect. The lip of the flower is of a brownish purple colour, with a blue blotch in the middle; and is oblong, with three lobes, the middle of which is divided into two. Thisspecies grows from six inches to a foot in height, and flowers from May to July. It is moderately common in the open spaces and on the banks of some calcareous districts.

Although a great variety of Grasses (orderGramineæ) are to be found on calcareous soils, there are two common species which are almost exclusively confined to dry, chalky pastures. One is the Downy Oat Grass (Avena pubescens), which flowers in June and July. It has a creeping stem, and grows from one to two feet high. The radical leaves are short, hairy, with sharply-pointed ligules, and terminate abruptly in a sharp point. The flowers are arranged in a nearly simple panicle, with erect spikelets of five or six flowers. The glumes are nearly equal, the inner one with three ribs. The flowering glume is divided at the tip, and provided with a long, bent, twisted bristle.

The other, numbered 7 onPlate VIII, is the Yellow Oat Grass (A. flavescens), which grows to about the same height, and flowers at the same time. In this species the radical leaves are hairy, and also terminate suddenly in a sharp point. The panicle is much branched, with erect spikelets of five or six flowers. In this one, too, the inner glumes have three ribs, but it may be distinguished from the last by the two terminal bristles of the inner scales, and by the blunt ligules (appendages at the base) of the sheathing leaves.

We have already dealt with flowers that grow in various damp situations, as moist meadows, woods, &c.; but there are a few such which seem to be particularly partial to the banks of rivers, streams, and ditches: short descriptions of these will be placed separately in the present chapter.

It will be understood from the foregoing remark that the species taken here form only a small proportion of the flowers that actually grow by the river side; for although the numerous species commonly seen in moist fields and meadows may flourish quite to the water's edge, yet there are not many which require the extreme wetness of soil that restricts them to the sodden banks of rivers and streams.

Our first example is the Common Meadow Rue (Thalictrum flavum). It belongs to the orderRanunculaceæ, but its pale yellow flowers do not, at first sight, suggest a resemblance to the buttercups, anemones, and other favourite flowers of this group, for they have no petals, very small sepals, and are rendered conspicuous only by their densely-clustered stamens, with their long, projecting, bright yellow anthers. The plant is erect, from two to four feet high; and flowers during July and August.

Passing over the Monk's-hood (Aconitum Napellus), so well known as a garden flower, which is occasionally seen wild near the banks of streams and ditches, we come to the Blue Meadow Crane's-bill (Geranium pratense)—one of the several species of pretty Wild Geraniums (orderGeraniaceæ). It is a downy plant, varying from one to four feet high, with an erect stem, swollen at the nodes; and opposite, roundish leaves, deeply divided into five or seven lobes with sharp segments. The flowers are of a bluish purple colour, an inch or more in diameter, usually arranged two on a stalk,the two pedicels spreading while in flower, but turned downwards when in fruit. The five sepals have long points, and the five petals are slightly notched. As in other species of the genus there are ten stamens, five shorter than the other five; and a five-lobed ovary, with an equal number of long styles, all attached to a long, central beak. The five carpels separate when ripe, and are raised by the curling of their styles. This flower is common in wet meadows, especially in the southern counties, and is usually more frequent along the banks of rivers and ditches, but it is sometimes also seen in wet thickets. It flowers in June and July.

The Common Meadow Rue.

The Hemp Agrimony (Eupatorium cannabinum), of the orderCompositæ, is very common along the banks of streams and on the borders of wayside ditches all over Britain. It would hardly be taken for a composite flower by those who are acquainted only with the more typical members of the order, but an examination of its rather dull lilac blossoms will soon reveal its affinity to the other members of the group, for the compact, terminal corymb is formed of numerous small heads, each consisting of about five tubular, perfect florets of equal size, surrounded by an involucre of a few overlapping bracts, and remarkable on account of their projecting styles, which are deeply divided into club-shaped branches. The plant is a large one, with erect, reddish stems, varying from two to six feet in height; and it flowers from July to September.

The Hemp Agrimony.

We have already noticed the Lesser Skull-cap (p.275), which is rather common on damp heaths, and there is another British member of the same genus—the Common Skull-cap (Scutellaria galericulata)—that is frequently seen on the banks of streams and in other wet places. The latter is a slightly downy plant, with a creeping stock, and a slender, branched stem from eight to sixteen inches high. Its leaves are opposite, as in other plants of the same order (Labiatæ), with very short stalks, and crenate or slightly-toothed edges. The flowers are in pairs in the axils of the leaves, almost sessile, and all turned towards the same side of the stem. On the back of the two-lipped calyx is a hollow, scale-like projection which gave rise to the popular name, for when the corolla falls, the lips of the calyx close over the ripening fruit, and the projection above mentioned then presents somewhat the appearance of a cap. The corolla is over half an inch long, of a dull blue colourwithout, but much paler inside. This plant flowers from July to September.

On the banks of streams and ditches we may often meet with the Comfrey (Symphytum officinale)—a coarse and rough but pretty plant belonging to theBoraginaceæ. It has a stout, branching stem, two or three feet high; and the stem-leaves extend downward on its surface forming wing-like ridges. The lower leaves are stalked, broader than the upper ones, generally from six to eight inches long; and all the leaves are rough with bristly hairs. The flowers are of a yellowish white or, sometimes, of a purple colour, and are arranged in forked, drooping, one-sided racemes. The calyx is deeply cleft into five lobes; and the corolla consists of a tubular portion, the top of which is closed by five narrow, fringed scales; and, above this, a wider bell-shaped part, of about the same length, with five small, reflexed teeth. This plant blooms during May and June.

The Common Skull-Cap.

The Yellow Loosestrife (Lysimachia vulgaris), of the orderPrimulaceæis a beautiful river-side plant, common in most parts, flowering during July and August. Its stem is stout, erect, branched,slightly downy, from two to three feet high; and its leaves are ovate or lanceolate, sessile, and arranged in opposite pairs or in whorls of three or four. The flowers are rather large, of a bright yellow colour, dotted with orange, and arranged in a large, pyramidal, leafy panicle. The calyx is deeply cleft into five pointed segments with hairy margins; and the broadly bell-shaped corolla is deeply divided into five wide lobes. All the five stamens are united by their filaments, forming a kind of cup around the ovary.

The Comfrey.

There is another beautiful Loosestrife—the Purple Loosestrife—that is often seen on river-banks; but as it is not particularly partial to this habitat, but rather grows in marshes and wet places generally, it is described in another chapter (XV). It should be noted, however, that the two plants are not so nearly allied as the popular names suggest; for while the one described above is of the Primrose family, the latter is a member of theLythraceæ, and differs in having a corolla of free petals.

Passing now to the orderPolygonaceæwe have to note the Great Water Dock (Rumex Hydrolapathum)—a smooth plant, varying from three to six feet in height, much resembling other Common Docks in general appearance, but found almost always on the borders of streams and ponds. Its leaves are lanceolate in form, usually pointed, and either flat or slightly curled at the margins. The upper ones taper down into the stalk; but the lower ones, which are from one to two feet long, are often heart-shaped at the base. The reddish-green flowers are closely-whorled, and form long panicles. The perianth is cleft into six parts, of which the three outer are smaller and covered with little tubercles, while the inner become enlarged and close over the triangular fruit. Each flower has six stamens and three very short styles. This plant is in flower during July and August.

A few species of Willows and Sallows that grow on the banks of streams belong to the orderSalicaceæ, and have the following features in common:—Their leaves are simple, stipulate, and deciduous. The flowers are imperfect, in erect catkins with small scales at the base, the male and the female flowers being produced on separate trees or shrubs. Each male flower consists only of a small scale and two or more stamens; and the female of a similar scale, and a conical ovary of one cell with a forked style. The fruit is a conical capsule of two valves, containing several seeds that are covered with white, silky hairs. The species referred to are the Almond-leaved and the Bay-leaved Willows, the Dark-leaved Sallow, and the Purple Osier, but we refrain from introducing descriptions since the identification of these trees is somewhat difficult for a beginner.

Several of our flowering plants are to be seen most frequently on walls and rocks, or in other situations where there is hardly a trace of soil of any kind. Some of these thrive in such dry spots, with often such free exposure to the rays of the spring or summer sun, that it is difficult to understand how they manage to survive the periods of drought through which they live until we become acquainted with certain peculiarities of their form and structure.

In the first place we must recall the fact that plants lose a considerable amount of moisture by evaporation from the transpirating surfaces of their leaves, and that this loss must necessarily be greatest when the air is warm and dry unless there is some means by which the transpiration is automatically regulated according to the requirements of the plant and to the varying conditions under which it has to exist.

The leaves of plants are covered with a thin skin orepidermiswhich consists of a single layer of cells, and which is practically impermeable to moisture. In this epidermis, however, on one or both sides of the leaf, are minute pores (stomata) through which water vapour is free to pass; and beneath the porous epidermis is a loose, cellular tissue, with air-spaces, from which the moisture can readily pass, in the form of vapour, to these stomata.

Each of the stomata is bordered by a pair of crescent-shapedguard-cells, placed with their concave sides towards each other, and joined at the ends. Further, the guard-cells are capable of changing their form, becoming straighter, and thus reducing or even closing the aperture between them; and becoming again curved, opening or enlarging the pore. The former change takes place during darkness, thus preserving the plant from the cooling effects of evaporation during the chilly nights; and also duringdry weather when the plant is in danger of losing much more moisture than the roots can absorb.

So far, however, we have been dealing with a regulating process that is common to green plants in general; but we must look for some additional protection against loss of moisture in the plants which grow in such places that they have to live through longer or shorter periods during which the roots have little or no moisture within reach.

From what has been said concerning the structure of the leaf it will be understood that, as a rule, the larger the surface the greater will be the loss of water in a given time. But when we examine the leaves of the plants that grow on dry walls and rocks, we frequently find that they are more or less thick and fleshy—that the material of the leaf is disposed in such a manner as to reduce the area of the surface as compared with other leaves made up of the same amount of tissue.

In some species this diminution of surface is carried to the extreme, and the leaves have become very thick, assuming a cylindrical or almost globular form; and such leaves are capable of absorbing and retaining large supplies of water that serve to maintain the plant during those periods in which the roots have no moisture within their reach.

We also find that many of the plants in question are further protected from a dangerous loss of moisture by the peculiar arrangement of their leaves, which are often so closely applied to the stem, or so closely overlapping one over another, that the total area of exposed surface is considerably reduced; and it frequently happens that the stem of the plant becomes thick and succulent, as well as the leaves, thus adding to the store of moisture kept in reserve for the rainless days.

While some plants are almost invariably found in dry, stony places, others are very diverse in their habitats, sometimes growing in moist and shady places, and sometimes on cliffs or other rocky situations. In the latter we often find considerable modifications of size, form and structure, the same species being more or less luxuriant and thin-leaved when in damp soils, while in rocky places it becomes more or less stunted, with a tendency to produce thick and succulent leaves.

A few of the plants that we include in the present chapter are to be found only on wet rocks, and are therefore of a nature very different from that of the species growing in dry places. They arealways well supplied with moisture; and, being usually surrounded by a damp atmosphere, they lose but little water by evaporation, and thus require no reserves within their leaves or stems.

Our first species is the well-known Wallflower (Cheiranthus cheiri), of the orderCruciferæ. It is a rather shrubby plant, frequent on old walls and ruins, where it flowers during April and May. Though too familiar to need any description, we may note that in the wild state it varies from six to twelve inches high, and bears sweetly-scented, yellow or orange flowers. The plant is not indigenous, but has now become naturalised as a wild flower in most parts of Britain.

The Wall Rocket (Diplotaxis tenuifoliaorBrassica tenuifolia), of the same order, is a very similar plant, growing in similar situations, but it does not commence to flower till the summer is somewhat advanced. Its stem is leafy, branched, smooth, woody towards the base, but more slender than that of the Wallflower; and its very variable leaves are generally three or four inches long, deeply divided pinnately into narrow segments with irregularly-toothed margins, and emit a rather unpleasant odour when rubbed. The flowers are of a pale yellow colour, fragrant, about three-quarters of an inch in diameter, in terminal racemes, with sepals more or less spreading; and the fruits are narrow, flattened siliquas, with membranous valves, about an inch and a half long. The plant is to be found principally in the southern counties of England, and flowers from July to September or early October.

On dry rocks, chiefly in the hilly and mountainous districts of North and West Britain, we meet with the Vernal Sandwort (Arenaria verna) of the orderCaryophyllaceæ. This is a little tufted plant, only from two to four inches high, with branched stems more or less decumbent at the base; and small, sessile, opposite, very narrow leaves, each with three veins. The starlike, white flowers are about a third of an inch across, on slender stalks, and grouped in terminal, loose, few-flowered cymes. They have five pointed sepals, less than a quarter of an inch long, each with three prominent veins; five spreading petals, a little longer than the sepals; ten stamens; and a superior ovary with three narrow styles. The fruit is a short ovate capsule which opens, when ripe, by three valves.

One of the Geraniums—the Shining Crane's-bill (Geranium lucidum)—is almost essentially a plant of walls and rocks. It is a beautiful species, smooth and shining in all its parts, with a tendency to turn red, like the Herb Robert; and, as in other plants of itsorder (Geraniaceæ), distinguished by the swollen joints of its stem. The leaves are almost round in general outline, but are deeply divided into five, broad, coarsely-toothed segments. The flowers are small, rose-coloured, and generally grow in pairs on axillary stalks. They have five, erect, wrinkled sepals, with long points; and five short, rather broad, entire petals. This species is common in most parts of Britain. It varies in height from six to eighteen inches, and flowers from May to September.

The Biting Stonecrop or Wall Pepper.

We have now to consider a few species of the orderCrassulaceæ, which includes some very interesting succulent plants that are peculiarly adapted to a life in the dryest of situations on walls, roofs, &c. In addition to the thick, fleshy nature of their stems and leaves, these plants are distinguished by terminal cymes or corymbs of flowers with (usually) five sepals, the same number of distinct petals, twice as many stamens arranged in two whorls, and carpels equal in number to the petals. Three of the plants referred to are known as Stonecrops, and may be recognised by the following descriptions:—

1. The English Stonecrop (Sedum anglicum).—A smooth plant, two or three inches high, abundant in rocky and stony places, especially in the West and near the sea, flowering from June to August. Its stems are more or less decumbent, much branched and rooting at the base; and its leaves are small, thick, almostglobular, of a pale green colour with, often, a tinge of red. On the small flowerless branches the leaves are very crowded and overlapping; but on the taller, flowering stems they are more scattered and placed alternately. The little starlike flowers are white, frequently tinged with pink or spotted with red, and arranged in a short, two-forked panicle. They have short, green sepals; narrow, sharply-pointed petals about twice the length; and stamens with bright red anthers.

The WallPennywort or Navelwort.

2. The White Stonecrop (S. album).—A somewhat similar plant, from three to seven inches high, sometimes seen in large clusters on rocks, walls, and roofs, bearing white or pinkish flowers during July and August. The whole plant is smooth; and its short creeping stock gives rise to short barren stems with crowded leaves, and erect flowering stems with scattered leaves. The leaves are very thick, of a bright green colour, about a third of an inch long, and oblong or cylindrical in form. The panicles are much branched, with, usually, reddish stems; and each consists of numerous flowers with short, blunt sepals, and narrow, oblong petals about three times as long. This species is not so common as either the last or the following.

3. The Biting Stonecrop or Wall Pepper (S. acre).—A smooth plant, of a yellowish green colour, biting to the taste, very common on rocks, walls and roofs, bearing golden yellow flowers during July and August. It has short, barren stems, covered with closely-overlapping leaves arranged in six rows; and erect flowering branches from two to four inches in height. The leaves are very small, thick, succulent, oval or almost globular in form. Theflowers, which are in small, terminal, three-cleft panicles, have very short, blunt sepals; and much longer, narrow, pointed petals.

The same order (Crassulaceæ) includes the House Leek (Sempervivum tectorum)—a plant which has been introduced into Britain, and is now commonly seen growing wild on rocks and on the roofs of country houses. Its spreading offsets give rise to globular tufts of flowerless shoots, and to thick, succulent, flowering stems that grow to a foot or more in height. The lower leaves are ovate, acute, thick, fleshy, edged with red, and arranged in a dense rosette; and the flowering stem, with its sessile leaves, is covered with a short, sticky down. The flowers are of a dull pink or purple colour, and are sessile along the spreading branches of the stem. They have usually about twelve short sepals; the same number of pointed petals, two or three times the length of the sepals; about twice as many stamens; and an ovary of as many carpels as there are petals and sepals. It is interesting to note that half the stamens—those forming the inner whorl—produce no pollen, and that their anthers are often modified into ovaries, the ovules of which, however, do not mature. This plant flowers in July and August.

The London Pride or St. Patrick's Cabbage.

Our last selection from this order is the Wall Pennywort or Navelwort (Cotyledon umbilicus)—a peculiar plant, common on rocks and walls in the South and West of England. It has a hardstock, producing an abundance of fleshy leaves early in the year, and flowering stems, from six to eighteen inches high, from June to August. The lower leaves are round, wavy, smooth, very succulent and brittle, and depressed in the centre where the long fleshy stalks are attached. Those of the stem have shorter stalks which are more and more removed from the centre from below upwards. The stem is thick and succulent, and bears a long raceme of pendulous yellow-green flowers on short stalks. Each flower has a very small calyx of five sepals; a cylindrical corolla, about a quarter of an inch long, with five short teeth; ten stamens, attached to the tube of the corolla; and a superior ovary.

The Mossy Saxifrage.

Several of the Saxifrages grow in rocky and stony places, and four or five species are sufficiently common to demand a notice here. The flowers of this group have a calyx of five sepals that is either quite free or more or less adherent to the ovary; a corolla of five petals; ten stamens, attached with the petals at the base of the calyx; and a two-celled ovary, with two distinct styles, containing several seeds.

Our first species is the London Pride, None-so-Pretty, or St. Patrick's Cabbage (Saxifraga umbrosa), a native of Irish mountains which has been introduced into Britain as a garden flower, and has now become established as a wild flower in many parts. Itsflowering stem grows from six to twelve inches high; and the small white or pink flowers bloom during June and July.

The Ivy-Leaved Toadflax.

The Starry Saxifrage (S. stellaris) is a somewhat similar plant, but much smaller, rarely exceeding six inches in height. It is frequent on wet rocks in the North, flowering in July and August. Its leaves are sessile, oblong or obovate, tapering towards the base, thin, and arranged in spreading rosettes; and the stem is leafless with the exception of little bracts at the base of the pedicels. The starlike flowers, larger than those of the last species, are white, with two yellow spots on each petal, and are arranged in a loose panicle on spreading pedicels. The calyx is adherent to the ovary only at the base, with its segments turned down on the pedicels; and the petals are narrow and spreading.

Another Northern species—the Yellow Mountain Saxifrage (S. aizoides)—is abundant on the wet rocks of mountainous districts, flowering from June to September. It is a tufted plant, with branched, decumbent, leafy stems, about six inches long; and crowded, narrow, fleshy leaves, about half an inch long, fringed with hairs at the base. The flowers are yellow, in a loose panicle. The calyx is yellow, like the petals, but much shorter, and erect; and the ovary is adherent to the short tube of the calyx to about half way up.

The Rue-leaved or Three-fingered Saxifrage (S. tridactylites) is asmall species, rarely exceeding four or five inches in height, common on walls in most parts of Britain, flowering from April to July. The whole plant is usually more or less tinged with red, and its erect stem is covered with fine glandular hairs. The radical leaves are very small, stalked, and undivided; those of the upper part of the stem are also small and entire, but sessile; and the intermediate leaves, lower on the stem, are palmately divided into three or five narrow segments. The small white flowers are placed singly on rather long terminal and axillary stalks; and the hairy calyx, which adheres to the ovary, has five blunt lobes less than half the length of the petals.

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