Part 27

The mode of the dispersion of the seeds is particularly interesting in this instance. When the seeds are ripe the ovary splits into three valves which spread out till they are at right angles to their former position. Each valve is closely packed with smooth, oval seeds; and, as the carpels dry, their sides, originally convex, become gradually straightened so that they press on the seeds. The result is that the seeds are detached from the placenta, one by one, and suddenly shot out to a distance sometimes exceeding a yard. The whole process may be observed by placing some ripe fruits on a large sheet of paper spread in a warm, airy room.

Another peculiarity of the violet is to be seen in its production of two distinct kinds of flowers. The spring flowers, which we know so well, are conspicuous, and are visited and pollinated by insects, but they produce few or no seeds. In the autumn another kind of flower is formed, inconspicuous ones that often possess no petals, and which do not open. These are fertilised by their own pollen, and produce abundance of seed.

Soon after the appearance of the Dog Violet--usually early in May--we meet with the flowers of the Wood Sorrel or Alleluia (Oxalis Acetosella), a plant which is often included with the Crane's-bills in the order Geraniaceæ, but sometimes placed in a separate small order (Oxalidaceæ) containing only three British species. It is a very pretty little plant, of an acid nature, springing from a creeping rhizome. The leaves are radical, ternate, hairy, and sensitive, folding vertically at night in such a manner that the lower surfaces, containing the stomata, are completely covered, and thus loss by evaporation prevented. The flowers are usually solitary and axillary, and the peduncle has two small bracts about half way up. There are five sepals, united below; five white or pinkish petals; and ten stamens, all united into one bundle, but five shorter than the others. The ovary is five-chambered, and the fruit is a capsule.

Like the Violet, this flower is particularly interesting both as to the nature of its flowers, and to the manner in which it scatters its seeds. It bears two kinds of flowers--the delicate spring flowers just described, which are barren; and the later inconspicuous blooms, without petals, and which do not open, but produce seeds. The latter kind of flower may be seen up to August and September.

When the ovary is ripe it splits longitudinally along five seams, but the seeds remain attached to the placenta. Now, the seed coat is made up of layers, one of the inner of which becomes highly strained as the ripening proceeds, while the outer coat is not so strained. When the seed is quite ripe the cell-walls of the deeper layer swell, thus exerting a pressure on the outer layer, which is at last rent. The edges of the slit formed suddenly roll back, and the seed is violently jerked out through the opening of the capsule immediately in front of it.

In April, and from this month to about the end of July, the Wood Strawberry (Fragaria vesca--order Rosaceæ) is in flower. There is no mistaking this species when in fruit, but at other times the Barren Strawberry (Potentilla Fragariastrum), also called the Strawberry-leaved Cinquefoil, is often confused with it. The latter may be known by the absence of runners.

The chief distinguishing features of the Wood Strawberry are the running stem; ternate leaves, with sessile, hairy, serrate leaflets; hairy, erect peduncles; and white flowers, about half an inch in diameter, on pedicels which droop when in fruit.

In shady woods grows the Sweet Woodruff (Asperula odorata--order Rubiaceæ)--a small, erect and smooth plant, seldom exceeding eight inches in height. The leaves are six to nine in each whorl, lanceolate, with small prickles on the margins. The flowers are white, in terminal panicles, and the fruit is rough with hooked hairs. The herb emits, when dry, a pleasant odour resembling that of new hay.

There are two Periwinkles (order Apocynaceæ), both of which have been introduced into Britain as garden flowers, but have become established as wild flowers in several parts. One of these--the Lesser Periwinkle (Vinca minor)--is moderately common, especially in the West, where it is often seen in thickets and other shady places, flowering during April and May. It has a trailing stem, from one to two feet long, rooting at the nodes; and short, erect, leafy, flowering branches. The leaves are opposite, narrow-elliptical, entire, and quite smooth; and the blue or violet flowers, which are about an inch in diameter, are solitary on short, erect stalks. The calyx is free, and deeply divided into five narrow segments; the corolla has a narrow tube, and five broad, spreading parts; there are five stamens, enclosed in the tube of the corolla; and the carpels are distinct at the base, but connected at the top by the single style.

The other species--the Greater Periwinkle (Vinca major)--is a very similar plant, but its leaves are broader, with minute hairs on the margin; the calyx segments are also hairy at the edges; and the corolla is larger, with a broad tube.

The Tooth-wort (Lathræa squamaria--order Orobanchaceæ) is a peculiar, fleshy, pinkish plant, to be found among decaying vegetable matter or at the roots of the Hazel, Elm and a few other trees. It is partly parasitic, deriving its nourishment from the roots of the trees to which it is attached, or sometimes obtaining its food partly or entirely from decaying leaves and stems. Its upright stem, which reaches a height of from five to ten inches, is covered with tooth-like, hollow scales, and bears a one-sided raceme of purple-brown flowers. This peculiar plant is not only a parasite on trees, but is also a carnivorous species, provided with the means of capturing and digesting very small animals, and a more detailed account of its form and habits will be found in our short chapter devoted especially to carnivorous plants.

The Bugle (Ajuga reptans, of the order Labiatæ), is a very abundant flower in moist woods and pastures, blooming in May and June. It has a short root-stock, generally with creeping runners; and erect, smooth flowering stems from three to twelve inches high. At the base is a tuft of obovate, radical leaves, from one to two inches long, gradually narrowed into the stalk, with wavy margins; and on the stem are shorter leaves, with very short stalks, the upper ones often deeply tinged with blue or purple. The flowers are blue (occasionally pink or white), and are arranged in whorls of from six to ten in the axils of the upper leaves, the whole forming a leafy spike. They have a five-cleft calyx; a corolla with a short, erect, notched, upper lip; and a longer lower lip with three spreading lobes, the middle one of which is broader and notched.

The stamens, of which there are two pairs, project beyond the upper lip of the corolla; and the four nutlets of the fruit are rough and united.

The Yellow Dead Nettle, Weasel-snout, or Archangel (Galeobdolon lutea or Lamium Galeobdolon) of the same order is very much like the White Dead Nettle (p. 102) in habit, but is rather more slender, and less branched. It is not a very common plant, but is abundant in certain localities, forming one of the conspicuous flowers of thickets, copses and shady hedgerows during May and June. Its leaves are opposite, stalked, ovate, acute, and coarsely toothed; and the handsome large yellow flowers are in dense whorls of from six to ten in the axils of the upper leaves. The calyx has five short teeth; and the corolla has a short tube, not much longer than the calyx, and two lips, the upper of which is arched, while the lower is spotted with red, and has three lobes.

Our next example, the lovely Primrose (Primula vulgaris or P. acaulis--order Primulaceæ), which so beautifully bedecks our woods and banks in April and May, is so well known that a description for purposes of identification is quite unnecessary.

There are two distinct forms of the primrose flower, often called the pin-eyed and the thrum-eyed, the two forms growing on different plants. The former has its stamens at a contracted portion of the tube, about half way down, and a style so long that the stigma is visible at the top of the tube. The latter has its stamens at the contracted throat of the tube, while the style is so short that the stigma is half-way down.

These two forms may be termed the long-styled and the short-styled primrose, respectively, and the difference is of great importance, inasmuch as it helps to bring about the cross-fertilisation of the flower.

The principal agents concerned in the transfer of pollen from one flower to another are the wind and insects, but it is evident that the work is done, in the case of the primrose, by insects; for not only do we find that the anthers and the stigma are protected from the wind, being more or less hidden in the tube of the corolla, but the showy corolla, the delicate scent emitted by the flower, and the nectar produced at the base of the tube all combine to encourage nectar-loving insects whose proboscis is long enough to reach the sweets.

While such an insect is sucking the nectar from a short-styled primrose, the base of its proboscis is rubbing pollen from the anthers at the top of the tube, and the removal of the pollen is assisted by the contracted throat of the corolla in this kind of flower. Should that insect then visit a long-styled flower, the base of the proboscis, now dusted with pollen, will transfer some of the pollen cells to the stigma. In the same way pollen will be transferred from the anthers of the long-styled to the short-styled flower, since the stamens and stigma respectively occupy corresponding positions in the tubes of the corollas.

On Plate I (Fig. 3) we represent the Lady's Slipper (Cypripedium Calceolus)--a rare and beautiful orchis found in some of the limestone woods of North England. Its stem is downy and leafy, reaching a height of about one foot. The leaves, of which there are three or four, are oblong and ribbed; and the one or two large flowers are brownish with the exception of the lip, which is yellow and inflated.

Two species of Garlic (order Liliaceæ) are also to be found in woods early in the season. They are both strong-smelling plants with bulbous roots, radical leaves, and flowers arranged in an umbel with membranous spathes. One--the broad-leaved Garlic or Ramsons (Allium ursinum)--is very common, grows to a height of from six to twelve inches, and flowers from April to June. The stem is bluntly triangular and leafless; and the broad, radical leaves are much like those of the Lily of the Valley. The flowers are white, and form a flat umbel with two sharply-pointed bracts at its base.

The second species--the Sand Leek or Sand Garlic (A. Scorodoprasum)--grows to two or three feet, and is found almost exclusively in sandy woods of North England, where it flowers a little later than the Ramsons. The stem-leaves are linear, and form two-edged sheaths; and the flowers, which are reddish-purple, are in a loose umbel. (Plate I, Fig. 4.)

The Star of Bethlehem (Ornithogalum umbellatum) is a pretty flower that was originally introduced for cultivation, but has now become well established as a wild flower in many parts of Britain. It is found chiefly in copses and thickets, especially in the neighbourhood of towns and villages, and flowers in April and May. It has an oval bulb containing an abundance of viscid sap; long narrow, limp, radical leaves; and a flowering stem from six to twelve inches high. The flowers are white, from six to ten in number, arranged in a raceme the lower stalks of which are lengthened in such a manner as to bring all the flowers to a level, thus giving the general appearance of an umbel. There is a membranous bract at the base of each pedicel; and each flower has a perianth of six free, spreading, persistent segments, marked outside with a central, green line, and having a nectary at the base.

The same order includes the well-known Blue-bell or Wild Hyacinth (Hyacinthus nonscriptus or Scilla festalis), which is occasionally confused with the Harebell of the order Campanulaceæ. The leaves of this plant are linear and channelled, and the drooping flowers form a raceme of from six to twelve blooms. The perianth is bell-shaped, composed of six united parts, usually blue, but rarely pink or white. The anthers are yellow, and as with all the plants of this order, the ovary is superior. (See Plate I, Fig. 5.)

In damp woods we often meet with the Hairy Sedge (Carex hirta), which grows from one to two feet high; and in similar situations, the Pendulous Wood Sedge (C. sylvatica)--a tufted species, with a weak, leafy stem, from two to three feet high, and flaccid leaves. The latter has a single terminal, male spikelet, of about an inch long; and slender, drooping female spikelets, of about the same length, on long stalks.

On Plate I, we also represent the Wood Melic Grass (Melica uniflora), a slender, graceful species which may be seen in woods, often in bloom as early as the beginning of May.

THE SPRING-FLOWERING TREES AND SHRUBS OF WOODS, THICKETS, AND HEDGEROWS

Having considered the principal low-growing flowers of the woods, we must now give some attention to the trees and shrubs of the same localities.