IIICLIMBING PLANTS

Pollen Cells throwing out their Tubes.

Should the reader desire to watch the growth of the pollen tubes, he can easily do so by shaking some pollen cells (preferably large ones, such as those of some lilies) on to a solution of sugar, and watching them at intervals with the aid of a lens. In the course of a few hours the pollentubes will be seen to protrude, and these eventually grow to a considerable length.

In order that the ovules of a flower may develop into seeds, it is necessary that they become impregnated by pollen from the anthers of the same species, and this is brought about in the following manner: The pollen cells having been transferred by some means to the mature stigma, they adhere to the surface of the latter, and, deriving their nourishment from the secretion of the stigmatic cells, as above described, proceed to throw out their tubes. These tubes force their way between the cells of the stigma and style, and enter the ovary. Each tube then finds its way to one of the ovules, which it enters by means of a minute opening in its double coat called the micropyle, penetrates the embryo-sac, and reaches the ovum or egg-cell. The ovule is now impregnated or fertilised, and the result is that the ovum divides and subdivides into more and more cells till at last an embryo plant is built up. The ovule has thus become a seed, and its further development into a mature plant depends on its being transferred to a suitable soil, with proper conditions as to heat and moisture.

If the flower concerned is a perfect one, and the ovules are impregnated by pollen from its own anthers, it is said to be self-fertilised; but if the pollen cells that fertilise the ovules have been transferred from a distinct flower, it is said to be cross-fertilised.

Now, it has been observed that although self-fertilisation will give rise to satisfactory results in some instances, producing seeds which develop into strong offspring, cross-fertilisation will, as a rule, produce better seeds. In fact, self-fertilisation is not at all common among flowers, and the pollen has frequently no effect unless it has been transferred from another flower. In a few cases it has been found that the pollen even acts as a poison when it is deposited on the stigma of the same flower, causing it to shrivel up and die. In many instances the structure and growth of the flower is such that self-pollination is absolutely impossible; and where it is possible the seedlings resulting from the process are often very weak.

It has already been hinted that the wonderful variety of form and colour exhibited by flowers has some connexion with this important matter of the transfer of pollen, and the reader who is really interested in the investigation of the significance of this great diversity will find it a most charming study to search into theadvantages (to the flower) of the different peculiarities presented, especially if he endeavours to confirm his conclusions by direct observations of the methods by which the pollen cells are distributed to the stigmas.

Pollen cells are usually distributed either by the agency of the wind or by insects; and it is generally easy to determine, by the nature of the flower itself, which is the method peculiar to its species.

A wind-pollinated flower is generally very inconspicuous. It produces no nectar, which forms the food of such a large number of insects, and has no gaudy perianth, nor does it emit any odour such as would be likely to attract these winged creatures. Its anthers generally shed an abundance of pollen, to compensate for the enormous loss naturally entailed in the wasteful process of wind-distribution, and the pollen is so loosely attached that it is carried away by the lightest breeze. Further, the anthers are never protected from the wind, but protrude well out of the flower; and the stigma or stigmas, which are also exposed, have a comparatively large area of sticky surface, and are often hairy or plumed in such a manner that they form effectual traps for the capture of the floating pollen cells.

An insect-pollinated flower, on the other hand, has glands (nectaries) for the production of nectar, and its perianth is usually of such a conspicuous nature that it serves as a signal to attract the insects to the feast. (In some instances the individual flowers are very small, but these are generally produced in such clusters that they become conspicuous through their number.) Often it emits a scent which assists in guiding the insects to their food. Its stamens are generally so well protected by the perianth that the pollen is not likely to be removed except by the insects that enter the flower; and the supply of pollen is usually not so abundant as in the wind-pollinated species, for the insects, travelling direct from flower to flower, convey the cells with greater economy. The stigmas, too, are generally smaller, and are situated in such a position that, when mature, they are rubbed by that portion of the insect's body which is already dusted with pollen.

As we watch the nectar-feeding insects at work, we not only observe that the flowers they visit possess the general characters given above as common to the insect-pollinated species, but also that, in many instances, the structure of the flower is such that the transfer of pollen from anthers to stigma could only be accomplished by the particular kind of insect which it feeds. Various contrivances arealso adopted by many flowers to attract the insects which are most useful to them, and to exclude those species which would deprive them of nectar and pollen without aiding in the work of pollination. Thus, some flowers are best pollinated by the aid of certain nocturnal insects, which they attract at night by the expansion of their pale-coloured corollas and by the emission of fragrant perfumes. These close their petals by day in order to economise their stores and protect their parts from injury while their helpers are at rest. Others require the help of day-flying insects: these are expanded while their fertilisers are on the wing, and sleep throughout the night.

We do not propose to give detailed accounts of the various stratagems by which flowers secure the aid of insects in this short chapter. Several examples are given in connexion with the descriptions of flowers in subsequent pages, but a few typical instances, briefly outlined here, will give the reader some idea of features which should be observed as flowers are being examined.

In many flowers the anthers and the stigma are not mature at the same time, and consequently self-pollination is quite impossible. With these it often happens that the anthers and stigma alternately occupy the same position, so that the same part of the body of an insect which becomes dusted with pollen in one flower rubs against the stigma of another.

Other flowers, such as the Forget-me-not, in which both stamens and stigma are ripe together, project their stigmas above the stamens at first, in order that an insect from another flower might touch the stigma before it reaches the stamens, and thus cross-pollinate them; and their stamens are afterwards raised by the lengthening of the corolla until they touch the stigma. Thus the flowers attempt to secure cross-pollination; but, failing this, pollinate themselves.

In the Common Arum or Cuckoo Pint, described on p.106, we have an example of a flower of peculiar construction, surrounded by a very large bract in which insects are imprisoned and fed until the anthers are mature, and then set free in order that they might carry the pollen to another flower of which the stigmas are ripe.

Sometimes the flowers of the same species assume two or three different forms as far as the lengths of the stamens and pistils are concerned, the anthers of one being of just the same height as the stigma of another, so that the pollen from the former will dust that portion of the body of the insect which rubs against the latterExamples are to be found among the Primulas, and in the Purple Loosestrife, both of which are described in their place.

In some flowers the stamens are irritable, rising in such a manner as to strike the insects that visit them; and in these cases the anthers almost invariably deposit pollen on that portion of the insect's body which is most likely to come in contact with the stigma of the next flower visited. Again, in Sages, the anthers are so arranged that they are made to swing, as on a see-saw, to exactly the same end.

These few examples will suffice to show that the structure and conformation of flowers are subservient to the one great purpose of securing the most suitable means of the distribution of pollen, and the student who recognises and studies the various forms of flowers in this connexion will find his work in the field doubly interesting.

Many plants have stems which grow to a considerable length, and which are at the same time too weak to support the plants in the erect position. A considerable number of these show no tendency to assume an upward direction, but simply trail along the surface of the ground, often producing root fibres at their nodes to give them a firmer hold on the soil and to absorb additional supplies of water and mineral food. Some, however, grow in the midst of the shrubs and tall herbage of thickets and hedgerows, or in some other position in which it becomes necessary to strive for a due proportion of light, and such plants would stand but a small chance in the struggle for existence if they did not develop some means of securing a favourable position among their competitors.

These latter are collectively spoken of as climbing plants; but it is interesting to note that in their seedling stage they are all erect, and it is only after they reach a certain height that they commence to assume some definite habit by which they obtain the necessary support, or to develop special organs by which they can cling to objects near them.

Some climbers produce no special organs for the purpose of fastening themselves to surrounding objects, but trust entirely to the wandering and more or less zig-zag nature of their feeble stems, and thus reach the open light merely by a process of interweaving, as in the case of the Hedge Bedstraw (Galium mollugo). Others adopt this same method of interweaving, but at the same time develop some kind of appendages to give them additional support. Thus, the Rough Water Bedstraw (G. uliginosum), which sometimes reaches a height of four or five feet, has recurved bristles all along its slender stem, and these serve as so many little hooks, holding the plant securely on to the neighbouring rank herbage of the marshor swamp in which it grows, while the rigid leaves further assist by catching in the angles of surrounding stems.

Another good example is to be seen in the common Goose-grass or Cleavers (G. aparine) of our hedgerows, which also reaches a height of four or five feet, and clings very effectually by means of the hooked bristles of its stems and leaves.

The Marsh Speedwell (Veronica scutellata), though it grows to a height of only one foot, is too weak to stand erect without support, and it has quite a novel method of securing the aid of the plants among which it grows. Its two topmost leaves at first stand erect over the terminal bud, so that they are easily pushed through the spaces in the surrounding herbage as the stem lengthens. They then diverge, and even turn slightly downwards, thus forming two supporting arms, the holding power of which is further increased by the down-turned teeth of their margins. This process is repeated by the new pairs of leaves formed at the growing summit of the stem, with the result that the plant easily retains the erect position.

Prickles of the Wild Rose.

The Wild Roses and Brambles growing in the hedgerows support themselves among the other shrubby growths by the interlacing of their stems, but are also greatly aided by the abundance of prickles with which these stems are armed. The prickles, even if erect, would afford considerable assistance in this respect; but it may be observed that they are generally directed downwards, and often very distinctly curved in this direction, and so serve to suspend the weak stems at numerous points.

We often find the Bramble growing in abundance on heaths and downs, in situations where suitable props do not exist. In this case the younger shrubs simply trail along the ground, or form low arches as the weight of the stems and their appendages cause the apex to bend to the ground. Yet if we turn to the older shrubs of several years' growth we find that they have succeeded in reaching a height of some feet. The first stems of these shrubs formed low arches as we have just described, and then they gave rise to branches which were first erect, but were afterwards bent downwards in the same manner, forming arches rising higher than their predecessors. This continued, year after year, till at last a long series of stems, forming arch above arch, reached the present height, the older stems, at the bottom, now dead, serving to support the whole mass above.

Ivy, Showing the Rootlets or Suckers.

Some climbing stems produce little roots by means of which they can cling firmly to available supports. Such are very common among tropical plants, but our Ivy affords a splendid example. The roots so formed may appear in clusters at special points of the stem, or in long lines running longitudinally on it, and they are produced on trailers as well as on climbers. In fact, we can draw no fine distinction between the former and the latter in this respect, and even the Ivy will sometimes trail along the ground after the manner of the Periwinkle, which roots itself at several points as it proceeds.

The rootlets of the Ivy and other climbers of the same habit always avoid the light; and if they are not originally formed on the side of the stem facing the supporting surface, they soon turn towards the latter, and give rise to little clinging suckers that firmly adhere. If they come in contact with a bare rock, or with a surface from which no nutriment can be derived, they serve the one purpose of clinging only; but if they reach even a small amount of nutritive soil, they produce absorbent fibres that are capable of extracting food.

The ivy usually clings to the bark of trees or to old walls, the crevices of which often contain some small amount of transported soil, or more or less organic soil formed by the growth and decay of low forms of vegetable life; and thus the tree is enabled to obtain a little food from the objects that give it the necessary mechanical support.

The well-known Virginian Creeper (Ampelopsis) produces rootlets by means of which it can cling to very smooth surfaces. Its light-avoiding 'tendrils' always turn to the wall or other supporting body; and, on coming in contact with it, give off little branches which diverge like the toes of the tree-frog, and produce little adhesive discs which hold on firmly by the aid of a sticky secretion.

Perhaps the most interesting of all climbing plants are those which twine their stems around the props afforded by the neighbouring growths. As before stated, the stems of these plants are erect when very young; but after they have reached a certain height the top of the stem bends to one side, and then, as the growth proceeds, it turns slowly round and round, describing a circle in the horizontal plane, thus seeking some support round which it can twine.

The rate at which the top of the stem revolves varies in different plants, and also in the same plant according to the temperature and other conditions affecting the growth. In some species the upper portion describes a complete circle in less than two hours during warm weather, while in others a single revolution may occupy one or two days.

It will be seen, from the nature of these movements, that the revolving stem is far more likely to come in contact with erect, rather than with horizontal supports, and observations made on twining stems will show that they seldom fix themselves round supports which are placed horizontally or only on a slight incline. In fact, some of these stems seem quite unable to twist themselvesspirally except round an axis that is either erect or forms a very large angle with the horizontal plane.

Should the twining stem succeed in reaching a favourable prop, it immediately commences to bend itself round and round, forming a more or less compact spiral; and it is probable that the slight pressure, caused by the contact, acts as a stimulus which incites the peculiar mode of growth.

The direction which the spiral takes is not always the same. In the Hop, Honeysuckle, and the Climbing Buckwheat or Black Bindweed, the direction is always the same as that of the hands of a clock; while in the Bindweeds the spiral is invariably contra-clockwise. Further, it is not possible to compel any species to turn in a direction opposite to that which it naturally follows. Its stem may be forcibly twined in the wrong direction any number of times, but the free end will always follow its natural course as soon as it is left undisturbed.

Stem of the Bindweed, Twining to the Left.

Should the stem of a young twining plant fail to reach a suitable support, it bends over, not being sufficiently rigid to support itself, and at last the apex reaches the ground. Then, starting afresh from this second position of rest, it begins to ascend, and its upper end again commences to revolve as before. The chances are that it will, from this second position, find something round which it can twine; but failing this its summit may again and again bend to the ground, thus renewing its attempts from various positions more or less distant from one another, and in each effort so made the revolving upper end of the stem gradually lengthens, and describes a larger and larger circle in search for a favourable prop.

A twining stem sometimes has the advantage of additional support afforded by the stiff nature of the base of the stem, which is often rendered still more rigid by a twist or torsion resembling that of the strands of a rope. Such advantage is often still further increased by the presence of longitudinal ridges of the stem, frequently bearing rows of hooked prickles or hairs that hold on toany object touched. Again, the base of the stem, even though it reaches nothing round which it can twine, sometimes takes the form of a spiral, thus forming a good foundation for the upper portion as it seeks out a convenient prop. Yet another contrivance to secure the same end may be observed in the Greater Bindweed and some other plants. The stems, failing to secure a favourable hold, twine round one another, thus producing a kind of rigid cable for the support of the upper extremities as they revolve in order to find stems round which to form their spirals.

Should all the methods and contrivances of the twining plant fail it in its attempts to secure an uppermost place among the surrounding herbage or shrubs, it is compelled to trail along the ground. But such a position is most disadvantageous and unnatural to it, and usually results in a stunted and sickly plant that may produce no flowers.

Most of the twining plants of our country are of short duration. Many, like the Climbing Buckwheat, are annuals; while others, as the Hop and the Bindweeds, though they have perennial roots, produce fresh stems each season. The Honeysuckle and the Bittersweet, however, have perennial, woody stems which increase in thickness year by year, though the latter does not twine very much, and seems to take an intermediate place between the typical twiners and the plants which support themselves by merely interlacing their stems with the neighbouring plants or shrubs.

Stem of the Hop, Twining to the Right.

Some twining stems are unable to form their spirals round thick supports, and after making some attempt to do so grow off at a tangent to seek some less bulky prop. It has been observed, for instance, that the Hop cannot grasp a pole that is more than four inches in diameter.

In many cases, too, the spirals of the twining stem increase in diameter after they are first formed, and can thus adapt themselvesto the increasing size of a living stem round which they have grown. The spirals of the Honeysuckle, however, do not increase in this way; and consequently, when they surround the trunk or branch of a young tree, the latter is constricted, often to such an extent that it is strangled and becomes stunted in its growth.

Another class of climbing plants cling to their surroundings by means of tendrils, which are modifications of leaves or shoots that grow spirally like the stems we have been considering.

Whatever be the origin of a tendril, it generally grows straight until it has reached some favourable support, and in order to obtain such support it performs circular movements similar to those of the tips of twining stems. Like these stems, too, the tendril is always sensitive, and forms a close spiral round the object it touches.

Some tendrils will grow spirally without ever touching a support, but these often become stunted and wither, while those which reach and embrace a stem or other structure are apparently incited to a luxuriant growth by the stimulating effect of the pressure produced.

When the tip of a tendril is successful in gripping a stem firmly, the portion behind it often takes part in the spiral movement, thus becoming shorter, and pulling the support towards its own plant in such a manner as to bring it within the reach of additional tendrils.

Of course the tendrilled plants have a much better chance of securing a suitable support than the twiners, for the latter have to depend on the searching and clinging powers of but one structure, while the tendrils are usually very numerous on the same plant, and throw themselves out in all directions in search of the required aid. The production of tendrils as a means of support is also much more economical than the method of clinging by a twining stem, for the former are usually very slender, while the latter must necessarily be sufficiently thick to convey the nutritive requirements of the whole plant; and thus the process of clinging by tendrils is more in accordance with the usual economy of Nature.

We have observed that twining stems can, as a rule, twine round only those supports which are erect or nearly so. This is not the case with tendrils, which are better adapted for twisting round horizontal stems and leafstalks. Often, too, they pass from one branch or leaf to another, and so secure the plant to which they belong by fastenings both above and below. Further, whilethe clasping part of a tendril often becomes hard and rigid, the portion between this and the plant may remain green and flexible. This latter portion also frequently forms a new spiral in the opposite direction, thus rendering the connexion between the plant and its support so supple and elastic that no damage is likely to accrue from the motions caused by the wind.

The tendrils which form long spirals are generally modified stems or leaves, or they may be elongated leaflets of a compound leaf. Those which are modified stems may be distinguished by their growth from the axils of the leaves, denoting that they had their origin in axillary buds after the manner of branches generally; and also, sometimes, by the fact that they bear imperfect leaves in the form of little scales. The tendrils of the Common or White Bryony (p.96) are of this nature; while those of the Grape Vine are either modified floral stems or altered flower-stalks.

In some cases the entire leaf may be changed into a tendril, in which instance its true nature is revealed by the presence of a bud in its axil, as in many ordinary foliage leaves. More frequently, however, the 'leaf-tendril' is an altered leaflet of a compound leaf, such as we see in the Peas and Vetches; and it is interesting to note in such cases that the loss entailed by the conversion of leaflets into tendrils is often compensated for by the formation of leaf-like stipules which are capable of performing the function of leaves. In fact, we often find that the size of the stipules is proportional to the number of tendrils produced; and that when the leaflets are considerably reduced in number by their conversion into tendrils, not only are the stipules large and leafy, but the stem itself may be extended laterally into broad wing-like expansions which do the work of foliage leaves.

Interesting illustrations of this are to be found in the Yellow Vetch—a rather rare plant sometimes seen in sandy fields—in which all the leaves are converted entirely into tendrils, and their function performed by very large leafy stipules; also in the Narrow-leaved Everlasting Pea of bushy places, in which the leaflets of the compound leaves are all converted into tendrils with the exception of two, the work of which is aided by the stipules and by the 'wings' of the stem and petioles. In the Rough-podded Vetch, too, the stems and petioles are winged to serve the same end; and other British members of this genus have either large stipules or winged stems, or both, to compensate for the loss of leaflets that have been modified into tendrils.

In other climbers the blade of the leaf is not reduced in size, even though the leaf serves the purpose of a tendril, the function of clinging being assigned exclusively to the petiole or leaf-stalk. This may be observed in the Wild Clematis and the Bryony, in both of which the petiole forms a ring round any branch or stem with which it comes in contact. These petioles are apparently equally sensitive on all sides, and are therefore ready to cling to any available support, whether above or below. In the Clematis the leaves are at first at right angles to the stem of the plant, but they afterwards turn downwards, and thus transform themselves into so many anchors which give additional aid in supporting the climber among the other hedgerow plants and shrubs.

The work of the botanist is light during the early spring, especially if his attention is directed only to plants and trees in their flowering stages; but, to one whose ambition is to study Nature in all her varied phases, this season of the bursting of the bud, when all things are awakening into new life, is full of interest, and demands no small amount of time.

The first flowers observed in the spring are mainly those hardy weeds which may be seen in bloom almost through the year, such as the Shepherd's Purse, Chickweed, Groundsel, White Dead Nettle, Red Dead Nettle, and Henbit Dead Nettle. These are soon followed by the Furze, Strawberry-leaved Cinquefoil, Snowdrop, Hazel, Common Whitlow-grass, and other flowers that are truly blossoms of the spring. All these will be described in turn, according to their various habitats; the object of the present short chapter being to note those signs of early spring which demand the attention of the lover of Nature while flowers are as yet few and inconspicuous.

A ramble over bleak downs and moors during the cold days of early spring will probably reveal but little of interest in the way of vegetable life, but in sheltered vales and woods, copses, and protected waysides, there is much to be observed. Here it is that we find the hardy weeds which have continued to bloom throughout the winter months; the earliest of the spring flowers; the fresh green foliage of herbs and shrubs that, in more exposed situations, have been completely denuded; the first tender seedlings appearing above the ground long before the frosts are over; and the expanding 'leaf-buds' showing their green while elsewhere all life seems dormant.

This is the season when the young botanist requires his notebook more than the collecting-book or vasculum; for his recordsof early flowers, and of the times of the appearance of the leaf in our trees and shrubs, will prove of great interest when compared with the corresponding events and times of other years. Not only do our spring seasons vary considerably from year to year in such a manner as to alter the general times of appearance of leaf and flower, but the vicissitudes of our climate even change the order in which these events occur.

The general study of the buds of trees should commence before they begin to burst. We commonly speak of the buds as winter buds, but it should be known that they were formed in the preceding summer or autumn, and have remained dormant throughout the winter. There is usually aterminal budat the tip of each twig, andlateral budsat the sides. If we examine a lateral bud we find immediately beneath it a more or less distinct scar, denoting the position of a leaf that fell in the autumn, thus showing that the bud in question was formed in the axil or angle of the leaf. These observations should be verified by examining the trees in autumn, while the leaves still exist.

It is not sufficient that we are able to recognise trees when in leaf; they should be known equally or almost as well during the winter and early spring while the branches are bare, and this is usually easily accomplished by making ourselves acquainted with the general form of each tree as viewed from a distance, and, on closer inspection, with the nature of the bark and the character of the buds.

All our forest trees are of the exogenous type; that is, their stems increase in thickness by the addition of new wood formed outside the older wood and underneath the bark. Thus the bark, which is composed of a layer or mass of dead, sapless cells, is gradually pushed outward as the stem thickens. The result is that the bark is either more or less fractured, as in the Elm and the Oak, or it flakes off and falls to the ground, as is the case with the Plane and the Birch. A new layer of bark is always formed during each summer, and this, in turn, either cracks or peels away; but while, in the former instance, the accumulated bark presents a very rugged appearance, and becomes very thick, in the latter case it remains smooth, and is always thin.

Then again, how are we to account for the great variety in the general forms of our different trees—the irregular, crooked nature of the Oak; the slender, but denser branching of the airy Birch; and the tall, pyramidal form of the Lombardy Poplar? All this is easily understood if we carefully observe the positions of the buds as seen during the winter months; and watch the development of these buds during early spring.

Trees in Winter or Early Spring1. Hazel, with catkins. 2. Ash. 3. Oak. 4. Lime, with remains of the last season's fruits.

If the buds are irregularly scattered on the twigs, the lateral buds being as strongly developed as the terminal ones, while, in the spring, as is often the case, certain only of the buds develop into new twigs, the others remaining dormant, then the branches assume that irregular, crooked appearance so characteristic of the Oak. If, on the other hand, all the terminal buds are well developed, and the lateral buds are weaker and more regularly distributed, but farther apart, then the tree grows more rapidly in height than in breadth, and assumes more nearly the character of the Pyramidal Poplar. It will thus be seen that the study of trees in their winter condition is not altogether lacking in interest.

Referring once more, but briefly, to the matter of dormant buds, we recommend the reader not only to observe that some buds do not expand with the others during the spring, but to make them the subject of experiment. Thus, when the Horsechestnut is well in leaf, dormant buds will usually be seen on the sides of the twigs, sheltered by the spreading leaves produced at the tips. Now remove the whole cluster of leaves formed by the terminal bud, together with the bud itself, and the hitherto dormant laterals, under the influence of increased light and warmth, and supplied with sap that is now directed into new channels, will speedily show signs of growth. Similarly, the fruit-gardener will remove the tips of the branches of his fruit trees, which often bear buds that are destined to produce leafy twigs only, and thus encourage the growth of the fruiting buds that are situated lower on the twigs.

Let us now briefly consider the structure of buds and the manner in which they are protected. Most buds are surrounded by brownish scales which are impervious to water, and thus prevent a loss by evaporation at a season when the activity of the roots in absorbing moisture from the soil is suspended. Such loss is still further insured in some cases by a covering of natural varnish. On removing this protective coat we find a dense cluster of closely-packed leaves, variously folded or crumpled in different species, and often, in the centre, a cluster of flowers.

What, then, is the true definition of a bud? It is a young branch, and may give rise to a mature branch bearing foliage leaves only, floral leaves only, or a combination of both. A transverse section of a bud, examined, if necessary, with the aid of the microscope, will show the nature of the branch it was destined to produce; and, in the case of buds which represent, in embryo, branches bearing flowers, or both leaves and flowers, it is often an easy matter to see the whorls of the future flowers, and even the pollen cells in the anthers and the ovules in the ovary.

Trees in Winter or Early Spring5. Birch, with catkins. 6. Poplar. 7. Beech. 8. Alder, with catkins and the old fruit 'cones' of the previous season.

Interesting as it is to study the structure of buds in their dormant condition during winter and early spring, even more fascinating is the watching of the gradual expansion of the bud and the unfolding of the young leaves. And it is not always necessary to make frequent visits to the woods in order to carry out such observations, for a large number of buds will develop almost equally well, at any rate through their earlier stages, if the twigs bearing them be placed in vessels of water either in or out of doors; and in many cases all the stages from dormant bud to perfect leaves and fully-expanded flowers may be watched in this way.

We have spoken of the protection afforded to the dormant bud during the winter period, but it is interesting to note that protection is necessary for the young leaves even after they have forced themselves well out into the light and air. The reason for this is that the epidermis or outer skin of the young leaf is not properly developed. It is not yet water-tight, and, consequently, the sap of the tender leaves would rapidly evaporate, so that they would soon become dry and shrivelled.

The means by which the young leaves are protected will be readily seen if we watch the gradual development of the bud. In many cases these leaves remain folded long after they have left the shelter of the original bud-scales, the manner of folding being the same as that which obtained while within the bud. Sometimes they are folded like a fan, or like the leaves of a book; sometimes rolled one within the other, or irregularly crumpled in such a manner that nothing is exposed to the air except the edges of the leaves and the surfaces of the veins.

In addition to the protection from evaporation afforded by the folding of the young leaves, many are covered with a dense coat of "wool." Young leaves of the Horsechestnut are very thickly covered with such a coat, of which only the slightest traces are to be seen in the fully-grown leaf. The young leaves of the Beech are folded like a fan for some time after they have left the enclosure of the bud, and the folding is such that the only parts exposed are the margins, the midrib, and the strongly-marked parallel veins. But since all these parts are provided with hairs, the young leaf, aslong as it is folded, is surrounded by a complete protective covering. As the epidermis develops, and the danger of loss by evaporation thus reduced, the leaf straightens itself out, and the hairs either fall or become shrivelled. The leaf of the Wayfaring Tree is protected, while young, by a complete covering of starlike hairs which form a fine felted coat over the whole surface; and when the epidermis is properly formed, the hairs are all shed.

Some young leaves are preserved by scaly stipules which surround them after they have emerged from the bud; and as soon as the epidermis is sufficiently impermeable the stipules, having done their work, fall to the ground. So great is the shower of these transient structures, in the case of the Oak, Elm, and Lime trees, that the ground is almost completely covered by them.

Twig of the Lime in Spring, Showing the Deciduous, Scaly Stipules.

Young leaves have yet another way of preventing the evaporation of their sap, and that is by turning themselves into the erect position so that the warmth of the spring sun has but little effect on them. The young leaves of various grasses turn their apices upwards; while those of the Horsechestnut, after having lost the protection afforded by the woolly covering and the original folding, turn themselves with their points downwards. Later, when the epidermis is well formed, and the leaves are so far developed that they are capable of utilising the energy of the sun in the performance of their functions, they take up the horizontal position.

Another interesting matter for spring observation is the relativetimes of the bursting of the flowering buds and the leafing buds on the same species of tree or shrub. In many cases the former are fully developed before the latter show any signs of active growth, or while the foliage is as yet only passing through its earliest stages. The Hazel catkins shed their abundance of pollen before the foliage buds show the slightest signs of green. The Blackthorn is white with snowy blossoms before a leaf appears. The upper twigs of the Elm appear fluffy in the distance through the formation of its flowers while the foliage buds are still dormant; and the Alder, Willow, Poplar and Aspen likewise produce full-blown catkins while their branches are otherwise bare. Of the trees above named, the Hazel, Elm, Alder, Poplar, and Aspen are dependent on the spring winds for the transfer of the pollen, but the pollination of the Willow and the Blackthorn is brought about by the agency of early insects which visit the flowers for the nectar they provide.

Seedling of the Beech, Showing the Cotyledons and the First Foliage Leaves.

The same spring sun which calls forth the new leaves and early flowers exerts its vivifying influence on the seeds that fell to the ground before the winter's frosts set in, and in sheltered places myriads of young seedlings of plants and trees may be found in their first stages of growth. The early history of a plant is as interesting a study as that of the mature specimen, and the young botanist will do well if he seeks out the germinating seeds and watches their development. This part of botanical study may, perhaps, be carried on more conveniently at home than in the field, for the seedlings may be grown in soil, wet sawdust, or in water alone, and the stages closely observed.

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.

One of our earliest spring flowers of the wood is the lovely Daffodil or Lent Lily (Narcissus Pseudo-narcissus) of the orderAmaryllidaceæ. 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.

The Daffodil.

During April and May we meet with the beautiful little Wood Anemone (Anemone nemorosa—orderRanunculaceæ), 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 ofthe 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.

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