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.
[Illustration: TREES IN WINTER OR EARLY SPRING
5. Birch, with catkins. 7. Beech. 6. Poplar. 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, as long 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.
[Illustration: TWIG OF THE LIMB 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 relative times
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.
[Illustration: 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.
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.
[Illustration: THE DAFFODIL.]
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.
[Illustration: THE WOOD ANEMONE]
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.
[Illustration: THE GOLDILOCKS.]
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.
[Illustration: THE WILD COLUMBINE.]
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.
[Illustration: THE DOG VIOLET.]
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.
[Illustration: THE WOOD SORREL.]
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.
[Illustration: THE SWEET WOODRUFF.]
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.
[Illustration: THE LESSER PERIWINKLE.]
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.