Part 6

The seed is a plant in embryo. It consists of a young root, a bud, and one or two seed-leaves or cotyledons. Some seeds contain nothing but the parts just named, and when this is the case the cotyledons contain a reserve of food material sufficient to maintain the developing plant until the root is enabled to absorb sufficient nutriment from the soil, and the first foliage leaves are so far advanced that they can absorb carbonic acid gas from the air, and build up with the aid of this gas, together with the food obtained from the soil, the compounds required by the growing plant.

Other seeds contain, in addition to the embryo, a reserve of nutrient material quite distinct from it; and in such instances the cotyledons have the power of taking up this reserve, changing it to a condition suitable to the requirements of the plant, and then distributing it to the growing parts.

In some seedlings the cotyledons will remain for some time within, or partially within the seed, in order that they may continue the absorption of this reserve; and while this process is going on the seed may remain below the surface of the soil, or it may be lifted into the air by the upward growth of the cotyledons themselves.

In cases where the cotyledons contain the food reserve for the seedling they sometimes remain under the soil, but in many instances they are pushed into the air by the upward growth of that portion of the plant axis immediately below them. In either case they decay as soon as their work is accomplished. This often happens as soon as they have delivered up to the seedling their reserve of food, but frequently the cotyledons which ascend into the air expand, becoming really leaflike in general appearance, assuming a green colour through the development of chlorophyll (the green colouring matter of plants), and then perform all the functions of the ordinary foliage leaves of the plant. Such cotyledons often continue to exist long after the first foliage leaves have appeared from the bud, for, although the original food reserve has been exhausted, they are now in a position to manufacture, under the combined influence of the sun's warmth and light, compounds essential for their own growth as well as that of the other parts of the seedling. These cotyledons, however, are never of the same form as the true foliage leaves.

The student should obtain a variety of seeds or seedlings of our wild plants and forest trees in order to study these interesting early stages. Such employment will prove very valuable at a season when there is but little call for outdoor work.

V

WOODS AND THICKETS IN SPRING

One of our earliest spring flowers of the wood is the lovely Daffodil or Lent Lily (_Narcissus Pseudo-narcissus_) of the order _Amaryllidaceæ_. This plant develops from a bulb--an underground bud formed of thick, fleshy leaves; and the flowers appear during March and April. The perianth is composed of a tube and six spreading limbs of a delicate yellow colour; and a deep, bell-shaped, golden coronet, beautifully notched and curled at the rim.

During April and May we meet with the beautiful little Wood Anemone (_Anemone nemorosa_--order _Ranunculaceæ_), often in such abundance that the ground beneath the trees is completely covered by its graceful leaves and flowers. The leaves are radical, stalked, and deeply lobed, springing from an underground stem. On the flower stalk, some distance below the flower, is a whorl of stalked bracts of the same form as the radical leaves. The flower has six spreading sepals, resembling petals, usually white, but often tinged with a delicate pink, or, more rarely, with blue. The fruit consists of a number of downy achenes.

Belonging to the same order (_Ranunculaceæ_) we have two species of Hellebore--the Green Hellebore (_Helleborus viridis_) and the Stinking Hellebore (_H. foetidus_), both found in woods on chalk or limestone during April and May. The former, also known in parts as the Bear's-foot (Plate I, Fig. 1), has leaves palmately lobed, consisting of five or seven parts; and the flowers, which are more than an inch across, have spreading green sepals, and small tubular petals which contain nectar that is supposed to be poisonous on account of the small dead flies that are commonly found sticking to it. The Stinking Hellebore, or Setterwort, has evergreen, radical leaves, the lobes of which do not radiate from a common centre; and the flowers, of which there are many on each peduncle, have erect sepals.

The Goldilocks or Wood Ranunculus (_Ranunculus auricomus_) is a flower very much like the Upright Meadow Buttercup (p. 211), though not nearly so tall, being only from six to ten inches high. It grows chiefly in thickets and copses, and flowers from April to July. Its root is fibrous; the stem erect, slender, and branched; the radical leaves long-stalked, round or kidney-shaped, divided into three, five, or seven lobes; and the stem leaves few, sessile, and palmately divided to the base into very narrow segments. The calyx is downy, consisting of spreading, yellow sepals; and the petals are often partially or entirely wanting. This plant is widely distributed, but is most frequent in the centre and south of England.

The Columbine (_Aquilegia vulgaris_), also one of the _Ranunculaceæ_, so well known as a garden flower, grows wild in the thickets and copses of several parts, blooming from May to July. Its branched stem grows to a height of one or two feet; and the leaves are stalked, with three broad, stalked, three-lobed segments. The pretty, drooping flowers are usually over an inch in diameter, of a white, blue, or purple colour, in a loose, leafy panicle. They have five coloured, deciduous sepals; five petals, each with a curved spur that projects below the base of the calyx; numerous stamens; and an ovary of five carpels which ripen into as many follicles.

The Dog Violet (_Viola canina_--Order _Violaceæ_) is probably too well known to need description, seeing that it is easily distinguished from the other species of the same genus by the absence of scent and by the presence of running stems. It is, however, very variable, both in its habits and habitats, so much so, indeed, that some botanists regard the varieties as distinct species under the titles of Wood Violet, Dark Wood Violet, Pale Wood Violet, Hill Violet, Bog Violet, &c. These different forms are distinguished by the shape of the leaves, which may be broadly-cordate, narrow-cordate, or lanceolate; and also by the nature of the stem and the form and colour of the spur of the corolla. In some the main stem is flowerless, but flowering stems proceed from the axils of its leaves; in others the main stem is long and branched, bearing flowers. The narrow-leaved and branched varieties occur principally on heaths, while the broad-leaved forms, in which the main stem is flowerless, are found chiefly in woods. The student will do well to compare as many forms as possible as an interesting study in variation.

The flowers have five sepals; and five unequal petals, usually of a bluish-purple colour, the lower one prolonged backward into a blunt spur. Five stamens closely surround the ovary, which is composed of three carpels, but is one-celled.

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.

VI

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.

This portion of the field-naturalist's work will be found at least as fascinating as the observation of the herbaceous plants, for although the flowers of trees are often small and very inconspicuous, many are really beautiful blossoms, and all present features of more or less interest to the botanist. Moreover, the observations of these flowers will always be coupled with those of the appearance and expansion of the leaves, for while some trees produce their flowers shortly before their leaves, and others after, leaves and flowers often come about the same time, and the period of the year covered by the present chapter--from about March to April or early June--will include the bursting of the leaf-buds and the expansion of the leaves of all our deciduous trees and shrubs. Opportunities should be made at this season to observe not only the parts of the trees just named, but to note all other characters presented by the trees, such as the nature of the trunk and its bark, the mode of branching, the appearance of the young twigs, and the nature of the soil and situation in which each species is found.

Our first example is the Barberry (_Berberis vulgaris_)--the only British representative of its order (_Berberaceæ_)--a smooth, pale-green shrub, from four to seven feet high, often seen in woods, thickets, and hedgerows, flowering in May and June. Its branches generally droop at the tips, and have triple spines at the base of each leaf or cluster of leaves. The latter are obovate, sharply toothed or even prickly, and often reduced to a cluster of spines. The flowers are pale yellow, in hanging racemes. Each has several yellow sepals, the outer of which are very small; six petals, in two whorls, with nectaries at their bases; and six stamens. The stamens at first lie on the petals; but they are very sensitive, and when the filaments are touched by an insect as it seeks the nectar at their bases, the stamens immediately spring upward, throwing off their pollen, and often depositing some on the insect's back. It is thus possible that the cross-pollination of the flowers is greatly aided by the insect, especially as it will often happen that the same part of its back which has been touched by the elastic stamen will come in contact with the stigma of another flower.