hypnoides_), a very variable plant, from three to ten inches high,
rather rare in South England, but much more common in the rocky parts of
North England and Scotland. It has numerous procumbent, barren stems
with tufted leaves; and erect flowering stems bearing a few small leaves
and a loose cyme of a few white flowers. Most of the leaves are narrow,
pointed, entire, about a quarter of an inch long; but the larger ones,
at the base of the plant, are about twice as long, and divided into
three or five narrow lobes. The calyx adheres to the ovary to about
two-thirds of the length of the latter, and has five lobes about
one-third as long as the petals. This species flowers from May to July.
Old walls, ruins, and limestone cliffs are frequently adorned with the
pretty flowers of the Snapdragon (_Antirrhinum majus_--order
_Scrophulariaceæ_) which bloom from July to September. The plant varies
from one to two feet in height, is tufted and leafy at the base, and has
erect stems which bear racemes of large flowers. The leaves are very
narrow and entire; and the flowers, which are usually white, pink or
crimson, are shortly stalked in the axils of the small upper leaves. The
calyx is deeply divided into broad lobes very much shorter than the
corolla; and the latter consists of a broad tube and two lips, the whole
being over an inch in length. The mouth of the flower is closed by a
projecting 'palate,' but is easily opened by pressing the flower at the
sides between finger and thumb. There are four stamens on the corolla,
two longer than the others; and the fruit is an unsymmetrical capsule
that opens when ripe by a few holes near the top.
The Ivy-leaved Toadflax or Mother of Thousands (_Linaria Cymbalaria_),
of the same order, is a pretty little trailing plant very commonly seen
on old walls in many parts of Britain, particularly in the South-West.
It will grow luxuriantly in places where there is no soil other than
that afforded by the crumbling mortar, and will often establish itself
even on new walls so compactly built that it is difficult to see how the
plant can find the necessary moisture or how its roots can penetrate the
hard material to which it is attached. Its slender stems vary from a few
inches to two feet in length, often rooting at the nodes; and its little
leaves are smooth, with three or five lobes, and generally of a purplish
colour on the under side. The little flowers, which bloom from May to
September, are of a pale blue or lilac colour. The lipped corolla is
very similar to that of the last species, with a yellowish palate
closing the mouth, but it has a short spur at the base.
The one remaining flower of this chapter is the Wall Pellitory
(_Parietaria officinalis_), which belongs to the Nettle family
(_Urticaceæ_). It is a somewhat bushy plant, varying from six inches to
two feet in height, bearing axillary clusters of small, sessile, green
flowers from June to September, and is common on walls and stony banks,
more especially in the South of England. Most of the flowers are usually
imperfect, and the clusters are surrounded by a whorl of a few divided
bracts. The males are few in number, each consisting of a hairy
perianth, and four stamens which are jointed and very elastic, springing
suddenly and shedding their pollen when touched; the females have a
tubular, hairy perianth of four lobes, and a single tufted stigma.
XXI
FIELD AND WAYSIDE IN AUTUMN
From the end of September onward the number of wild flowers is rapidly
decreasing, but still there is much to be seen that will be interesting
to the observant student of Nature. Many of the summer flowers are quite
over, while others continue to bloom till, at last, they succumb to the
intensifying frosts; but hundreds of species of the summer-flowering
plants are now in fruit, and some of these are almost as interesting in
this stage as when in flower. Many plants will have been observed in
flower before any of their fruits were fully formed, but autumn is the
season when a large number of these may be seen in full fruit, and
watched as they make arrangements for the dispersal of their seeds.
We have already given (p. 12) an outline classification of the
various kinds of fruits, and if the reader will study this during the
autumn months, and examine the field and woodland plants that fall in
his way, he will find abundance of work awaiting him on every country
ramble.
A large number of wind-dispersed fruits and seeds are ripe long before
the autumn sets in, and have already been distributed by the summer
breezes; but now, with fewer flowers to attract attention, one can give
more time to the observations of the movements of tufted and winged
seeds and fruits as they sail through the air. And, as we brush by the
hedgerows and the borders of fields in search of various flowers and
fruits, we soon become acquainted with a variety of bristled, hooked,
and barbed fruits that are effectually dispersed by the agency of
animals, quite a large number of these having securely fastened
themselves to our clothing.
Many fruits remain attached to their plants long after the last flowers,
and even the leaves, have entirely disappeared. Some of these await the
gales of late autumn and winter, and being now no longer sheltered from
the wind, are carried to the spots where they are to produce new plants
in the following spring; while sheep and other animals, wandering
farther afield in search of food, carry away numerous hooked fruits in
their woolly or hairy coats.
The feathered fruits of the Wild Clematis adorn the hedgerows throughout
the greater part of the cold season, and form a striking feature of the
wayside until they have been dispersed by the winter storms; and the
hips of the Wild Rose, as well as the berries and drupes of various
shrubs, now rendered more conspicuous by their bright colouring and the
absence of foliage, are devoured by birds which afterwards deposit the
indigestible and, therefore, uninjured seeds, with their excrement, at
some distant spot.
Should the reader be interested in the various ways in which the
dehiscent fruits discharge their seeds, he will do well to collect a
number of species, as yet unopened, and expose them to the sun in a dry
place. He will then be able to note not only the directions and extent
of the dehiscence, but also to observe the forcible ejection of seeds by
those which split elastically, or which, by other mechanical
contrivances, have the power of throwing their seeds a considerable
distance.
We may find still another subject for study in the beautiful autumn
tints assumed by the leaves of many plants. Such tints are, of course,
most conspicuous in the foliage of our forest trees and shrubs; and,
when speaking of these, we shall have a word or two to say with regard
to the nature of the internal changes that give rise to the beautiful
display of colours; but not a few of the hedgerow herbs and shrubs
exhibit tints equally rich and varied. Note, for instance, the pretty
Herb Robert, still in flower in sheltered places, its blossoms standing
out beyond a background of richly-coloured leaves.
The vigorous summer growth of flowery banks and hedgerows is often
closely trimmed with the sickle for the greater convenience of
pedestrians and vehicular traffic, all the flowers and overhanging twigs
being closely cut, and the wayside thus destroyed from the
Nature-student's point of view; but the ground so denuded has recovered
itself by the autumn, and a second crop of flowers, arising from the old
stocks, often later than their normal season, is frequently the result.
A considerable number of summer flowers continue to bloom during the
autumn months, while a few are truly autumnal, and are not to be found
till the summer has nearly or quite passed.
In corn-fields we may still meet with the beautiful Pheasant's-eye
(_Adonis autumnalis_), and in fields the Hairy Buttercup (_Ranunculus
hirsutus_), the Daisy (_Bellis perennis_) and the Red Hemp-nettle
(_Galeopsis Ladanum_) are yet in flower, while the Annual Meadow Grass
(_Poa annua_) continues to produce new flowers to the end of the year.
On sunny banks in chalk districts we still see the delicate Rock Rose
(_Helianthemum vulgare_); and on banks almost everywhere the Wild Clary
(_Salvia Verbenaca_), and the still more hardy Milfoil (_Achillea
millefolium_), Knapweeds (_Centaurea nigra_ and _C. Scabiosa_), Field
Scabious (_Knautia arvensis_), Dark Mullein (_Verbascum nigrum_) and the
Toadflax (_Linaria vulgaris_).
Then, on downs and heaths we find the Yellow Bedstraw (_Galium verum_),
the crimson flowers of the Fine-leaved Heath (_Erica cinerea_), and the
rose-coloured or white blossoms of the Heather or Ling (_Calluna
vulgaris_): also the Carline Thistle (_Carlina vulgaris_), with its
inner involucral bracts broadly spreading while the sun shines, but bent
inwards to protect the florets during dull weather when the insects are
at rest, the lilac flower-heads of the Devil's-bit Scabious (_Scabiosa
succisa_) and the Small Scabious (_S. Columbaria_), and the conspicuous
flowers of the Chamomile (_Anthemis nobilis_), all standing out in bold
relief against the background of autumnal foliage.
Still more numerous are the autumn flowers of the waysides. By the dry
and dusty roadside we see the yellow flowers and silvery leaves of the
Silver-weed (_Potentilla anserina_), the little starlike flowers of the
Chickweed (_Stellaria media_), the yellow flower-heads of the Dandelion
(_Taraxacum officinale_), Sow Thistle (_Sonchus oleraceus_) and
Groundsel (_Senecio vulgaris_), the straggling Knot-grass (_Polygonum
aviculare_), the Spotted Persicary (_Polygonum Persicaria_), the
Shepherd's Purse (_Capsella Bursa-pastoris_), the Scentless Mayweed
(_Matricaria inodora_), the Chamomile (_Anthemis nobilis_), the White
Goose-foot (_Chenopodium album_), and Oraches (_Atriplex hastata_ and
_A. patula_). Where the soil is more generous we find the Herb Robert
(_Geranium Robertianum_), the Fleabane (_Inula dysenterica_), Red and
White Dead-nettles (_Lamium purpureum_ and _L. album_), and the Petty
Spurge (_Euphorbia Peplus_); while on old walls the Pellitory
(_Parietaria officinalis_) is still in flower.
XXII
AUTUMN IN THE WOODS
Although several of the flowers mentioned in the last chapter as
blooming during the present season may be seen along the borders of
woods, yet within the wood itself we are struck by the almost total
absence of flowers. This loss, however, is compensated for by the
beautiful and varied tints assumed by the leaves of the trees and
shrubs.
Important changes are now taking place in these perennial members of the
vegetable world in preparation for the coming winter. The temperature of
the soil is becoming considerably reduced, and, as a result, the
absorbing activity of the roots is greatly decreased, while the winter
is coming, when the temperature will be so low at times that the
circulation of the sap will practically cease. If the leaves remained on
the trees, they would give off from their surfaces more water than the
trees could obtain from the soil through their inactive roots, thus
endangering the lives of the trees. The leaves, therefore, must be shed.
But these leaves contain a considerable amount of nutritious material
which they themselves have built up, and which should not be lost. They
contain starch, albumen, and other compounds which would be entirely
lost to the trees if the leaves were shed in their present condition,
except that a small proportion, in the form of products of
decomposition, might be re-absorbed.
This being the case, arrangements must be made, first, for the passage
of the nutritious material in the leaves to some other part of the tree
where it can be stored for the winter; and, second, for the removal of
the leaves as the roots become less active.
So, before the time of leaf-fall, the nutritious substances in the
leaves, including the _chlorophyll_ to which the leaf owes its green
colour, become changed, and pass back to the stems or the root, where
they can be safely stored for the winter. The leaves, thus impoverished,
become mere skeletons--mere collections of empty, lifeless cells; and if
no further change takes place, they assume a very pale colour, like the
leaves of the Hornbeam, Birch, and the Willows.
But the transfer of the nutrient matter from leaf to stem or root is
accompanied by numerous chemical changes by which new compounds are
formed. Among these new substances a dark blue compound called
anthocyanin is produced in some plants; and where this exists in
considerable quantities we find the leaves of a dark bluish-green
colour, like that of the autumn foliage of the Pine.
Acids are also sometimes formed as a result of the complicated chemical
changes that take place during the transfer above described; and these
react on the anthocyanin present, changing its colour to a tint that
varies according to the proportion and quantity in which they exist.
Thus, if anthocyanin is present, together with a small amount of acid,
the leaves are turned violet, as in the case of the autumn leaves of the
Dogwood and the Spindle Tree; or purple, like those of the Service Tree.
A larger proportion of acid produces, with the anthocyanin, the brownish
green tint of the Alder leaves; or the brownish yellow of the Oak; while
still larger proportions will turn the anthocyanin yellow, orange, red,
or scarlet, according to the quantity in which the latter is present.
Thus we can account for the rich yellow of the Maple in autumn, the
orange of the Aspen leaves, the beautiful scarlet tints of the Mountain
Ash and the Barberry, and the grand display of varied colours exhibited
by the autumn Beeches.
Again, before the leaves are shed, the buds that are destined to produce
the new branches of the following spring are already formed. These may
be seen on all deciduous trees and shrubs, some of them in the axils of
the leaves, and others at the tips of the present twigs. Each bud is the
embryo branch of the following year. Some of them are destined to
produce leafy branches only; some are to develop into branches bearing
both floral leaves and flowers; while others are to produce flowers
without floral leaves; and it is interesting to note that, even at this
stage, sections of the buds, examined with the aid of a microscope, will
reveal the future leaves and flowers compactly concealed within their
scaly, protective coverings.
In October we may see the well-formed catkins of the Birch that are to
bloom in the following April, in company with the ripe fruiting catkins
of the present year. The Alder also bears its catkins that are to flower
five months later, together with the woody remains of the female catkins
of the previous spring; and the Hazel may be seen with its ripe nuts and
its future flowers both on the same twig.
[Illustration: THE ALDER IN AUTUMN, WITH THE CATKINS WHICH MATURE IN THE
FOLLOWING SPRING.]
The leaves, having manufactured the materials necessary for the
formation of the buds that are to produce the leaves and flowers of the
following year, and then transferred their remaining store of nutrient
matter to a suitable storehouse for the winter, are now practically
empty and lifeless. Had they remained alive and active, they would have
endangered the life of the tree by giving off more moisture than could
be replaced by the inactive roots. In their present, lifeless condition
they are useless to the tree; but by falling to the ground, and
decomposing where they lie, they improve the soil by the addition of
organic matter as well as of the mineral salts they contained.
In countries where a moderate temperature is maintained throughout the
year, the growth of plants and trees goes on without interruption, and
the fall of the leaf is hardly noticeable; for the older leaves die and
fall one by one, as they become incapable of performing their functions
for want of light, and new ones are being continuously formed close to
the tips of the twigs. But where the growth is interrupted, either in
hot countries during periods of drought, or in temperate countries by
the approach of a cold season, the whole of the foliage is shed within a
short period, and new leaves as suddenly appear when favourable
conditions return.
In our own latitudes, as we all know, the defoliation of the trees is
caused by the approach of cold weather, which decreases the activity of
the roots, so that the leaves become dry and lifeless. It is very
commonly supposed that the fall of the leaf is caused by frost; but this
is not the case. The leaves are shed during the cool days of autumn,
even though the temperature does not fall to freezing point; but it is
equally certain that the leaf-fall is accelerated by the frost when it
comes, for the little moisture remaining in the leaves is then frozen,
rendering the structures so brittle that they are easily snapped by the
wind.
The real cause of the rupture of the leaf is the formation of what is
called the '_separation layer_.' This consists of soft, succulent cells,
really in several layers, which are formed across the leaf-stalk,
usually at the base, where the bundles of vessels passing from the twig
to the leaf are narrower. The walls of these cells are thin, and are
easily separated; and as they extend inwards from the surface all round,
they break through the old cells, thus weakening the junction. When the
growth of the separation layer is complete, it requires very little
force to break off the leaf, and the process is aided by the formation
of certain organic acids which act on the cell-walls, causing them to
dissolve; and when the leaf has finally separated from the twig, it will
be found that the scar left is a clean-cut surface, such as would be
produced by the incision of a sharp knife.
The recognition of the above facts introduces to us a difficulty for
which we can find no explanation:--If the leaf-fall is not caused by
frost, but by certain structural alterations that take place in the tree
itself, how are we to account for the fact that the tree produces the
changes which are necessary for its own preservation every year, just at
the proper season? Plants and trees do not foresee the coming period of
cold weather that necessitates the performance of the functions which
they execute, and yet they instinctively prepare for the winter in the
manner described above.
Our autumn observations teach us that there are interesting differences
in the times and progress of leaf-fall of different species of trees,
and also of trees of the same species when exposed to different external
conditions. On open ground, where the trees are fully exposed both to
the sun's rays and to the cool autumn breezes, the leaves lose their
moisture and fall earlier than would the same species in more sheltered
situations; and they retain their moisture and position latest in damp,
shady woods. On high hills, where the exposure is extreme, the leaves,
which, by the way, do not appear till late in the spring, fall early on
account of the low temperature, and consequent decrease of root
activity, in the autumn.
Further, we note that while in some trees, such as the Ash, Hornbeam,
Beech and Hazel, the leaves fall first at the tips of the branches, and
the defoliation extends fairly regularly towards the trunk, in other
species, including Willows, Poplars, and the Lime, the branches become
bare first at their bases, and finally at their tips.
Even during the depths of winter we may see a number of dead leaves
still attached to the twigs of certain trees, notably the Oak and the
Beech; but where we find practically all the foliage remaining on the
tree or on special branches of a tree, we may generally assume that the
tree, or the branches in question, are dead--that they died during the
summer, before the separation layers of the leaves had been formed. We
can also understand, from what has been said, why the dead leaves remain
attached to a cut branch, and yet fall from the living tree from which
it was severed.
In our own country some plants and trees retain their leaves throughout
the year, so that we speak of them as evergreens. Many of these include
herbaceous plants of a hardy nature, some of which remain fresh and
green even in exposed situations, while others grow in more sheltered
places. In either case they are plants whose roots remain more or less
active in the cold season; and some of them, especially the evergreen
shrubs, have rather thick leaves which contain a considerable quantity
of sap, and which are surrounded by an outer covering or epidermis that
does not allow the water within to pass out so readily as in the case of
the deciduous leaves.
In addition to the observations previously mentioned, we should do well,
at this season of the year, to study the autumn fruits of our trees and
shrubs, most of which still remain attached to the twigs.
[Illustration: THE ASH IN AUTUMN, WITH ITS 'KEYS.']
Some of these fruits lose most of their moisture as they ripen, thus
becoming very light, and are provided with wings that cause them to be
dispersed more or less by the wind.
The so-called 'keys' of the Ash are one-seeded fruits, extended at the
end into a long, narrow wing with a slight twist. As a result of this
peculiarity they usually fall less rapidly to the ground, spinning as
they descend, and are thus carried farther than they otherwise would be
by the wind. The fruits of the Sycamore and the Maple are somewhat
similarly winged, and each of these consist of two carpels which
separate sooner or later--generally after they have reached the ground.
[Illustration: THE MAPLE IN FRUIT.]
On the Birch trees we may now see the ripe female catkins, consisting of
hundreds of minute fruits, closely packed together, each provided with a
wing on either side. They are very light, and easily blown a
considerable distance by the wind; and late in the autumn we may observe
the stalks of the catkins, from which some of the fruits have been
blown, still on the trees.
The wings that thus aid in the dispersion of fruits are not always part
of the fruit itself. In the Hornbeam it is a three-lobed, persistent
bract that performs this function; and the fruits of the Lime are also
blown away by the aid of a large bract from the middle of which the
fruit-stalk projects.
[Illustration: THE WAYFARING TREE, IN FRUIT.]
Some of our trees present a glorious aspect during the autumn months,
displaying conspicuous and more or less brightly-coloured fruits in
combination with the varied autumn tints of their leaves. The red
foliage of the Mountain Ash or Rowan is accompanied by the still
brighter clusters of scarlet fruits--little apple-like pomes, about the
size of holly 'berries'; and the Wayfaring Tree bears pretty clusters of
flattened, oval, one-seeded berries which are first red, and then nearly
black. The Guelder Rose, while still in full leaf, is often very heavily
laden with its bright red, semi-transparent berries; and the violet
foliage of the Dogwood is intermingled with clusters of little
berry-like drupes which, at first green, have now changed to a rich
purple-black. Then there is the Spindle Tree, with its pretty red lobed
capsules which split, when ripe, at its angles, disclosing as many cells
as there are lobes (usually four), each with a single seed enclosed in
an orange jacket. Occasionally we meet with the Strawberry Tree, during
early autumn, bearing both flower and fruit at the same time. This tree
flowers in September and October, but the fruits which accompany the
flowers are those of the previous year, for they require more than
twelve months to come to maturity. The fruit is a large berry, of an
orange-red colour, with a granulated surface that gives it somewhat the
appearance of the strawberry. It should be mentioned that the
Strawberry Tree is not indigenous to England, and is seldom seen outside
parks and gardens; but it grows wild in Ireland, and is very abundant
round Killarney and in other parts.