(_A. flavescens_), which grows to about the same height, and flowers at
the same time. In this species the radical leaves are hairy, and also
terminate suddenly in a sharp point. The panicle is much branched, with
erect spikelets of five or six flowers. In this one, too, the inner
glumes have three ribs, but it may be distinguished from the last by the
two terminal bristles of the inner scales, and by the blunt ligules
(appendages at the base) of the sheathing leaves.
XIX
BY THE RIVER SIDE
We have already dealt with flowers that grow in various damp situations,
as moist meadows, woods, &c.; but there are a few such which seem to be
particularly partial to the banks of rivers, streams, and ditches: short
descriptions of these will be placed separately in the present chapter.
It will be understood from the foregoing remark that the species taken
here form only a small proportion of the flowers that actually grow by
the river side; for although the numerous species commonly seen in moist
fields and meadows may flourish quite to the water's edge, yet there are
not many which require the extreme wetness of soil that restricts them
to the sodden banks of rivers and streams.
Our first example is the Common Meadow Rue (_Thalictrum flavum_). It
belongs to the order _Ranunculaceæ_, but its pale yellow flowers do not,
at first sight, suggest a resemblance to the buttercups, anemones, and
other favourite flowers of this group, for they have no petals, very
small sepals, and are rendered conspicuous only by their
densely-clustered stamens, with their long, projecting, bright yellow
anthers. The plant is erect, from two to four feet high; and flowers
during July and August.
Passing over the Monk's-hood (_Aconitum Napellus_), so well known as a
garden flower, which is occasionally seen wild near the banks of streams
and ditches, we come to the Blue Meadow Crane's-bill (_Geranium
pratense_)--one of the several species of pretty Wild Geraniums (order
_Geraniaceæ_). It is a downy plant, varying from one to four feet high,
with an erect stem, swollen at the nodes; and opposite, roundish leaves,
deeply divided into five or seven lobes with sharp segments. The flowers
are of a bluish purple colour, an inch or more in diameter, usually
arranged two on a stalk, the two pedicels spreading while in flower,
but turned downwards when in fruit. The five sepals have long points,
and the five petals are slightly notched. As in other species of the
genus there are ten stamens, five shorter than the other five; and a
five-lobed ovary, with an equal number of long styles, all attached to a
long, central beak. The five carpels separate when ripe, and are raised
by the curling of their styles. This flower is common in wet meadows,
especially in the southern counties, and is usually more frequent along
the banks of rivers and ditches, but it is sometimes also seen in wet
thickets. It flowers in June and July.
[Illustration: THE COMMON MEADOW RUE.]
The Hemp Agrimony (_Eupatorium cannabinum_), of the order _Compositæ_,
is very common along the banks of streams and on the borders of wayside
ditches all over Britain. It would hardly be taken for a composite
flower by those who are acquainted only with the more typical members of
the order, but an examination of its rather dull lilac blossoms will
soon reveal its affinity to the other members of the group, for the
compact, terminal corymb is formed of numerous small heads, each
consisting of about five tubular, perfect florets of equal size,
surrounded by an involucre of a few overlapping bracts, and remarkable
on account of their projecting styles, which are deeply divided into
club-shaped branches. The plant is a large one, with erect, reddish
stems, varying from two to six feet in height; and it flowers from July
to September.
[Illustration: THE HEMP AGRIMONY.]
We have already noticed the Lesser Skull-cap (p. 275), which is
rather common on damp heaths, and there is another British member of the
same genus--the Common Skull-cap (_Scutellaria galericulata_)--that is
frequently seen on the banks of streams and in other wet places. The
latter is a slightly downy plant, with a creeping stock, and a slender,
branched stem from eight to sixteen inches high. Its leaves are
opposite, as in other plants of the same order (_Labiatæ_), with very
short stalks, and crenate or slightly-toothed edges. The flowers are in
pairs in the axils of the leaves, almost sessile, and all turned towards
the same side of the stem. On the back of the two-lipped calyx is a
hollow, scale-like projection which gave rise to the popular name, for
when the corolla falls, the lips of the calyx close over the ripening
fruit, and the projection above mentioned then presents somewhat the
appearance of a cap. The corolla is over half an inch long, of a dull
blue colour without, but much paler inside. This plant flowers from
July to September.
On the banks of streams and ditches we may often meet with the Comfrey
(_Symphytum officinale_)--a coarse and rough but pretty plant belonging
to the _Boraginaceæ_. It has a stout, branching stem, two or three feet
high; and the stem-leaves extend downward on its surface forming
wing-like ridges. The lower leaves are stalked, broader than the upper
ones, generally from six to eight inches long; and all the leaves are
rough with bristly hairs. The flowers are of a yellowish white or,
sometimes, of a purple colour, and are arranged in forked, drooping,
one-sided racemes. The calyx is deeply cleft into five lobes; and the
corolla consists of a tubular portion, the top of which is closed by
five narrow, fringed scales; and, above this, a wider bell-shaped part,
of about the same length, with five small, reflexed teeth. This plant
blooms during May and June.
[Illustration: THE COMMON SKULL-CAP.]
The Yellow Loosestrife (_Lysimachia vulgaris_), of the order
_Primulaceæ_ is a beautiful river-side plant, common in most parts,
flowering during July and August. Its stem is stout, erect, branched,
slightly downy, from two to three feet high; and its leaves are ovate or
lanceolate, sessile, and arranged in opposite pairs or in whorls of
three or four. The flowers are rather large, of a bright yellow colour,
dotted with orange, and arranged in a large, pyramidal, leafy panicle.
The calyx is deeply cleft into five pointed segments with hairy margins;
and the broadly bell-shaped corolla is deeply divided into five wide
lobes. All the five stamens are united by their filaments, forming a
kind of cup around the ovary.
[Illustration: THE COMFREY.]
There is another beautiful Loosestrife--the Purple Loosestrife--that is
often seen on river-banks; but as it is not particularly partial to this
habitat, but rather grows in marshes and wet places generally, it is
described in another chapter (XV). It should be noted, however, that the
two plants are not so nearly allied as the popular names suggest; for
while the one described above is of the Primrose family, the latter is a
member of the _Lythraceæ_, and differs in having a corolla of free
petals.
Passing now to the order _Polygonaceæ_ we have to note the Great Water
Dock (_Rumex Hydrolapathum_)--a smooth plant, varying from three to six
feet in height, much resembling other Common Docks in general
appearance, but found almost always on the borders of streams and ponds.
Its leaves are lanceolate in form, usually pointed, and either flat or
slightly curled at the margins. The upper ones taper down into the
stalk; but the lower ones, which are from one to two feet long, are
often heart-shaped at the base. The reddish-green flowers are
closely-whorled, and form long panicles. The perianth is cleft into six
parts, of which the three outer are smaller and covered with little
tubercles, while the inner become enlarged and close over the triangular
fruit. Each flower has six stamens and three very short styles. This
plant is in flower during July and August.
A few species of Willows and Sallows that grow on the banks of streams
belong to the order _Salicaceæ_, and have the following features in
common:--Their leaves are simple, stipulate, and deciduous. The flowers
are imperfect, in erect catkins with small scales at the base, the male
and the female flowers being produced on separate trees or shrubs. Each
male flower consists only of a small scale and two or more stamens; and
the female of a similar scale, and a conical ovary of one cell with a
forked style. The fruit is a conical capsule of two valves, containing
several seeds that are covered with white, silky hairs. The species
referred to are the Almond-leaved and the Bay-leaved Willows, the
Dark-leaved Sallow, and the Purple Osier, but we refrain from
introducing descriptions since the identification of these trees is
somewhat difficult for a beginner.
XX
ON WALLS, ROCKS, AND STONY PLACES
Several of our flowering plants are to be seen most frequently on walls
and rocks, or in other situations where there is hardly a trace of soil
of any kind. Some of these thrive in such dry spots, with often such
free exposure to the rays of the spring or summer sun, that it is
difficult to understand how they manage to survive the periods of
drought through which they live until we become acquainted with certain
peculiarities of their form and structure.
In the first place we must recall the fact that plants lose a
considerable amount of moisture by evaporation from the transpirating
surfaces of their leaves, and that this loss must necessarily be
greatest when the air is warm and dry unless there is some means by
which the transpiration is automatically regulated according to the
requirements of the plant and to the varying conditions under which it
has to exist.
The leaves of plants are covered with a thin skin or _epidermis_ which
consists of a single layer of cells, and which is practically
impermeable to moisture. In this epidermis, however, on one or both
sides of the leaf, are minute pores (_stomata_) through which water
vapour is free to pass; and beneath the porous epidermis is a loose,
cellular tissue, with air-spaces, from which the moisture can readily
pass, in the form of vapour, to these stomata.
Each of the stomata is bordered by a pair of crescent-shaped
_guard-cells_, placed with their concave sides towards each other, and
joined at the ends. Further, the guard-cells are capable of changing
their form, becoming straighter, and thus reducing or even closing the
aperture between them; and becoming again curved, opening or enlarging
the pore. The former change takes place during darkness, thus preserving
the plant from the cooling effects of evaporation during the chilly
nights; and also during dry weather when the plant is in danger of
losing much more moisture than the roots can absorb.
So far, however, we have been dealing with a regulating process that is
common to green plants in general; but we must look for some additional
protection against loss of moisture in the plants which grow in such
places that they have to live through longer or shorter periods during
which the roots have little or no moisture within reach.
From what has been said concerning the structure of the leaf it will be
understood that, as a rule, the larger the surface the greater will be
the loss of water in a given time. But when we examine the leaves of the
plants that grow on dry walls and rocks, we frequently find that they
are more or less thick and fleshy--that the material of the leaf is
disposed in such a manner as to reduce the area of the surface as
compared with other leaves made up of the same amount of tissue.
In some species this diminution of surface is carried to the extreme,
and the leaves have become very thick, assuming a cylindrical or almost
globular form; and such leaves are capable of absorbing and retaining
large supplies of water that serve to maintain the plant during those
periods in which the roots have no moisture within their reach.
We also find that many of the plants in question are further protected
from a dangerous loss of moisture by the peculiar arrangement of their
leaves, which are often so closely applied to the stem, or so closely
overlapping one over another, that the total area of exposed surface is
considerably reduced; and it frequently happens that the stem of the
plant becomes thick and succulent, as well as the leaves, thus adding to
the store of moisture kept in reserve for the rainless days.
While some plants are almost invariably found in dry, stony places,
others are very diverse in their habitats, sometimes growing in moist
and shady places, and sometimes on cliffs or other rocky situations. In
the latter we often find considerable modifications of size, form and
structure, the same species being more or less luxuriant and thin-leaved
when in damp soils, while in rocky places it becomes more or less
stunted, with a tendency to produce thick and succulent leaves.
A few of the plants that we include in the present chapter are to be
found only on wet rocks, and are therefore of a nature very different
from that of the species growing in dry places. They are always well
supplied with moisture; and, being usually surrounded by a damp
atmosphere, they lose but little water by evaporation, and thus require
no reserves within their leaves or stems.
Our first species is the well-known Wallflower (_Cheiranthus cheiri_),
of the order _Cruciferæ_. It is a rather shrubby plant, frequent on old
walls and ruins, where it flowers during April and May. Though too
familiar to need any description, we may note that in the wild state it
varies from six to twelve inches high, and bears sweetly-scented, yellow
or orange flowers. The plant is not indigenous, but has now become
naturalised as a wild flower in most parts of Britain.
The Wall Rocket (_Diplotaxis tenuifolia_ or _Brassica tenuifolia_), of
the same order, is a very similar plant, growing in similar situations,
but it does not commence to flower till the summer is somewhat advanced.
Its stem is leafy, branched, smooth, woody towards the base, but more
slender than that of the Wallflower; and its very variable leaves are
generally three or four inches long, deeply divided pinnately into
narrow segments with irregularly-toothed margins, and emit a rather
unpleasant odour when rubbed. The flowers are of a pale yellow colour,
fragrant, about three-quarters of an inch in diameter, in terminal
racemes, with sepals more or less spreading; and the fruits are narrow,
flattened siliquas, with membranous valves, about an inch and a half
long. The plant is to be found principally in the southern counties of
England, and flowers from July to September or early October.
On dry rocks, chiefly in the hilly and mountainous districts of North
and West Britain, we meet with the Vernal Sandwort (_Arenaria verna_) of
the order _Caryophyllaceæ_. This is a little tufted plant, only from two
to four inches high, with branched stems more or less decumbent at the
base; and small, sessile, opposite, very narrow leaves, each with three
veins. The starlike, white flowers are about a third of an inch across,
on slender stalks, and grouped in terminal, loose, few-flowered cymes.
They have five pointed sepals, less than a quarter of an inch long, each
with three prominent veins; five spreading petals, a little longer than
the sepals; ten stamens; and a superior ovary with three narrow styles.
The fruit is a short ovate capsule which opens, when ripe, by three
valves.
One of the Geraniums--the Shining Crane's-bill (_Geranium lucidum_)--is
almost essentially a plant of walls and rocks. It is a beautiful
species, smooth and shining in all its parts, with a tendency to turn
red, like the Herb Robert; and, as in other plants of its order
(_Geraniaceæ_), distinguished by the swollen joints of its stem. The
leaves are almost round in general outline, but are deeply divided into
five, broad, coarsely-toothed segments. The flowers are small,
rose-coloured, and generally grow in pairs on axillary stalks. They have
five, erect, wrinkled sepals, with long points; and five short, rather
broad, entire petals. This species is common in most parts of Britain.
It varies in height from six to eighteen inches, and flowers from May to
September.
[Illustration: THE BITING STONECROP OR WALL PEPPER.]
We have now to consider a few species of the order _Crassulaceæ_, which
includes some very interesting succulent plants that are peculiarly
adapted to a life in the dryest of situations on walls, roofs, &c. In
addition to the thick, fleshy nature of their stems and leaves, these
plants are distinguished by terminal cymes or corymbs of flowers with
(usually) five sepals, the same number of distinct petals, twice as many
stamens arranged in two whorls, and carpels equal in number to the
petals. Three of the plants referred to are known as Stonecrops, and may
be recognised by the following descriptions:--
1. The English Stonecrop (_Sedum anglicum_).--A smooth plant, two or
three inches high, abundant in rocky and stony places, especially in the
West and near the sea, flowering from June to August. Its stems are more
or less decumbent, much branched and rooting at the base; and its leaves
are small, thick, almost globular, of a pale green colour with, often,
a tinge of red. On the small flowerless branches the leaves are very
crowded and overlapping; but on the taller, flowering stems they are
more scattered and placed alternately. The little starlike flowers are
white, frequently tinged with pink or spotted with red, and arranged in
a short, two-forked panicle. They have short, green sepals; narrow,
sharply-pointed petals about twice the length; and stamens with bright
red anthers.
[Illustration: THE WALL PENNYWORT OR NAVELWORT.]
2. The White Stonecrop (_S. album_).--A somewhat similar plant, from
three to seven inches high, sometimes seen in large clusters on rocks,
walls, and roofs, bearing white or pinkish flowers during July and
August. The whole plant is smooth; and its short creeping stock gives
rise to short barren stems with crowded leaves, and erect flowering
stems with scattered leaves. The leaves are very thick, of a bright
green colour, about a third of an inch long, and oblong or cylindrical
in form. The panicles are much branched, with, usually, reddish stems;
and each consists of numerous flowers with short, blunt sepals, and
narrow, oblong petals about three times as long. This species is not so
common as either the last or the following.
3. The Biting Stonecrop or Wall Pepper (_S. acre_).--A smooth plant, of
a yellowish green colour, biting to the taste, very common on rocks,
walls and roofs, bearing golden yellow flowers during July and August.
It has short, barren stems, covered with closely-overlapping leaves
arranged in six rows; and erect flowering branches from two to four
inches in height. The leaves are very small, thick, succulent, oval or
almost globular in form. The flowers, which are in small, terminal,
three-cleft panicles, have very short, blunt sepals; and much longer,
narrow, pointed petals.
The same order (_Crassulaceæ_) includes the House Leek (_Sempervivum
tectorum_)--a plant which has been introduced into Britain, and is now
commonly seen growing wild on rocks and on the roofs of country houses.
Its spreading offsets give rise to globular tufts of flowerless shoots,
and to thick, succulent, flowering stems that grow to a foot or more in
height. The lower leaves are ovate, acute, thick, fleshy, edged with
red, and arranged in a dense rosette; and the flowering stem, with its
sessile leaves, is covered with a short, sticky down. The flowers are of
a dull pink or purple colour, and are sessile along the spreading
branches of the stem. They have usually about twelve short sepals; the
same number of pointed petals, two or three times the length of the
sepals; about twice as many stamens; and an ovary of as many carpels as
there are petals and sepals. It is interesting to note that half the
stamens--those forming the inner whorl--produce no pollen, and that
their anthers are often modified into ovaries, the ovules of which,
however, do not mature. This plant flowers in July and August.
[Illustration: THE LONDON PRIDE OR ST. PATRICK'S CABBAGE.]
Our last selection from this order is the Wall Pennywort or Navelwort
(_Cotyledon umbilicus_)--a peculiar plant, common on rocks and walls in
the South and West of England. It has a hard stock, producing an
abundance of fleshy leaves early in the year, and flowering stems, from
six to eighteen inches high, from June to August. The lower leaves are
round, wavy, smooth, very succulent and brittle, and depressed in the
centre where the long fleshy stalks are attached. Those of the stem have
shorter stalks which are more and more removed from the centre from
below upwards. The stem is thick and succulent, and bears a long raceme
of pendulous yellow-green flowers on short stalks. Each flower has a
very small calyx of five sepals; a cylindrical corolla, about a quarter
of an inch long, with five short teeth; ten stamens, attached to the
tube of the corolla; and a superior ovary.
[Illustration: THE MOSSY SAXIFRAGE.]
Several of the Saxifrages grow in rocky and stony places, and four or
five species are sufficiently common to demand a notice here. The
flowers of this group have a calyx of five sepals that is either quite
free or more or less adherent to the ovary; a corolla of five petals;
ten stamens, attached with the petals at the base of the calyx; and a
two-celled ovary, with two distinct styles, containing several seeds.
Our first species is the London Pride, None-so-Pretty, or St. Patrick's
Cabbage (_Saxifraga umbrosa_), a native of Irish mountains which has
been introduced into Britain as a garden flower, and has now become
established as a wild flower in many parts. Its flowering stem grows
from six to twelve inches high; and the small white or pink flowers
bloom during June and July.
[Illustration: THE IVY-LEAVED TOADFLAX.]
The Starry Saxifrage (_S. stellaris_) is a somewhat similar plant, but
much smaller, rarely exceeding six inches in height. It is frequent on
wet rocks in the North, flowering in July and August. Its leaves are
sessile, oblong or obovate, tapering towards the base, thin, and
arranged in spreading rosettes; and the stem is leafless with the
exception of little bracts at the base of the pedicels. The starlike
flowers, larger than those of the last species, are white, with two
yellow spots on each petal, and are arranged in a loose panicle on
spreading pedicels. The calyx is adherent to the ovary only at the base,
with its segments turned down on the pedicels; and the petals are narrow
and spreading.
Another Northern species--the Yellow Mountain Saxifrage (_S.
aizoides_)--is abundant on the wet rocks of mountainous districts,
flowering from June to September. It is a tufted plant, with branched,
decumbent, leafy stems, about six inches long; and crowded, narrow,
fleshy leaves, about half an inch long, fringed with hairs at the base.
The flowers are yellow, in a loose panicle. The calyx is yellow, like
the petals, but much shorter, and erect; and the ovary is adherent to
the short tube of the calyx to about half way up.
The Rue-leaved or Three-fingered Saxifrage (_S. tridactylites_) is a
small species, rarely exceeding four or five inches in height, common on
walls in most parts of Britain, flowering from April to July. The whole
plant is usually more or less tinged with red, and its erect stem is
covered with fine glandular hairs. The radical leaves are very small,
stalked, and undivided; those of the upper part of the stem are also
small and entire, but sessile; and the intermediate leaves, lower on the
stem, are palmately divided into three or five narrow segments. The
small white flowers are placed singly on rather long terminal and
axillary stalks; and the hairy calyx, which adheres to the ovary, has
five blunt lobes less than half the length of the petals.
[Illustration: THE WALL PELLITORY.]