Part 48

The Climbing Bistort (Polygonum convolvulus--order Polygonaceæ), also known as the Climbing Buckwheat, Climbing Persicaria, and Black Bindweed, is a very troublesome corn-field weed, with the climbing habit of the Convolvulus, often strangling the plants round which it twines its angular stem. It varies from one to four feet in height; and its alternate leaves are heart-shaped or arrow-shaped, pointed, with short membranous stipules at the base of the stalk. The flowers are small, pale green, in little loose clusters of from four to twelve. The lower clusters are stalked in the axils of the leaves, and the upper ones form irregular, terminal racemes. The five segments of the calyx are bluntly keeled, and occasionally winged; and the three outer ones closely envelop the fruit--a triangular nut. The plant flowers from July to September.

At least two or three of the Spurges (Euphorbiaceæ) are commonly seen in cultivated fields, but one in particular--the Dwarf Spurge (Euphorbia exigua)--is common in corn fields. It is a slender, smooth plant, usually from two to ten inches high, with several ascending stems diverging from near the base. The little yellow flowers are in terminal umbels of from three to five rays, sometimes very much contracted; and their glands (see p. 207) are crescent-shaped, with their fine points turned outwards. The time of flowering is July to October.

Our last example of the corn-field plants is the Wild Oat Grass or Havers (Avena fatua)--an erect grass, two or three feet high, with rough leaves, and stem hairy at the joints. Its flowers form a loose, spreading panicle, from six to nine inches long; with three-flowered spikelets, about an inch long, on very slender stalks, erect at first but afterwards drooping. The outer glumes are about three quarters of an inch long, tapering to a bristly point, often tinged with purple; and the inner ones, two or three in number, are a little shorter, cleft at the top into pointed lobes, and covered outside with yellowish-brown hairs. The awn is about twice as long as the spikelet, twisted at the base, and usually bent near the middle. This grass flowers during June and July.

XVIII

ON THE CHALK

While some flowers are so universally distributed that they may be described as existing almost everywhere, others are restricted to certain kinds of localities, outside which they seldom occur. This restriction is sometimes merely one of light and shade, the same species growing almost equally luxuriantly in open spaces, or, in shady places, regardless of other conditions. Some plants, however, are particularly partial to certain conditions of soil, situation, or climate, and are consequently more strictly confined to limited districts.

We have already referred to several species which are essentially flowers of the woods, but even these are not distributed evenly in wooded districts; for while some seem to be more universally scattered throughout our wooded parts, others show a decided partiality to particular soils, being found exclusively, or almost so, either in sandy woods, clayey woods, or woods in limestone districts, &c. In fact, the nature of the soil is such an important factor in determining plant distribution that we naturally associate many species with the particular rock strata on which we almost invariably find them.

So intimately is the distribution of plants connected with that of the geological strata that when, in the course of a day's ramble, we find a more or less sudden change in the nature of the flora, we may be almost sure that there is a corresponding change in the nature of the rocks or soil over which we have strayed; and the young botanist will find much to interest him in the study of this relation between vegetable life and geological structure. Of course we do not mean that the botanist must necessarily be also a geologist, but that he should, at least, be always ready to observe the nature of the habitats of the flowers he finds, noting particularly the kind of soil on which they grow.

Chalky districts are notably attractive to the lover of flowers; for, not only do they yield a number of species that are almost essentially the offspring of calcareous soils, but also produce other blossoms, often in rich profusion, that are less restricted in their habitats.

In the present chapter we shall note the principal flowers that grow principally or entirely in calcareous districts, the first being the Pasque Flower (Anemone Pulsatilla--order Ranunculaceæ), rare, it is true, but too beautiful to be omitted from our selection. This flower, shown on Plate VIII, Fig. 5, may be seen on some chalky hills during May and June. It is of a silky nature, and the lovely purple blossoms often reach a diameter of an inch and a half. The leaves are doubly or trebly pinnate, with very narrow segments which increase in length after the flowers have faded. The bracts, which are some distance below the flower, have also linear segments; and the flowers droop while still in the bud, but the peduncle becomes erect as they expand. The stamens are yellow, and the fruits are provided with feathered hairs.

On chalky, sandy, and other dry soils we may meet with the Round Prickly-headed Poppy (Papaver hybridum--order Papaveraceæ), very much like the Common Poppy in general appearance, but readily distinguished by its general hairy character, and, more especially, by the globular, furrowed fruit covered with spreading bristles. The flowers vary from one to two inches in diameter, and the crimson or deep scarlet petals are often black at the base.

The Bitter Candytuft (Iberis amara--order Cruciferæ), which is so well known as a border-flower of our gardens, grows freely in some of the chalk districts of the South and East of England. Unlike most of the Crucifers, the flowers are not symmetrical, the two outer petals being much larger than the others. The inflorescence is a raceme, which, like that of the Wallflower, becomes longer as the flowering proceeds; and the colour of the petals is white, lilac or red. The height of this plant varies from six to nine inches, and the flowers bloom during July and August.

The Wild Mignonette (Reseda lutea--order Resedaceæ) is very common in some chalky districts, generally in fields and other open ground, and may be easily recognised by its close resemblance to the well-known Sweet Mignonette (R. odorata), which is so highly valued as a garden flower on account of its pleasant perfume. It is of a shrubby nature, from one to two feet high, with scattered, stipuled leaves, the lower of which are pinnate, while the upper are three-lobed. The flowers are irregular, yellow, and arranged in short, conical racemes. The six sepals are unequal and linear; and the petals, also six in number, are very unequal, while the posterior one is divided into many parts. The flowers bloom throughout the summer.

One of the most characteristic flowers of the chalk is the pretty Rock Rose (Helianthemum vulgare--order Cistaceæ), which is often so abundant that it completely covers large patches of banks and pasture-land. The plant is of a procumbent nature, with woody stems, and opposite, flat, oval or oblong leaves, green above and hoary beneath. The yellow flowers are from three-quarters to an inch in diameter, and are arranged in racemes. There are five sepals, two of which are very small; and the numerous stamens are sensitive, spreading out and lying on the petals when the flower is squeezed. The time of flowering is from June to September.

An allied species--the Hoary Rock Rose (H. canum or H. marifolium)--may be found in the limestone districts of the West of England, flowering from May to July. The plant is very similar to the last, but the leaves are not stipuled, are smooth or hairy above, and very hoary beneath. The flowers, too, are much smaller.

A species of Violet--the Hairy Violet (Viola hirta--order Violaceæ)--may be found in some limestone and chalk districts, and also on some dry soils removed from calcareous rocks. It has no runners like those of other species, and its cordate leaves are very hairy, on petioles covered with spreading hairs. The flowers are scentless, pale violet or white, with bracts below the middle of the peduncle; and the spur of the corolla is long, blunt, flattened, and hooked.

Two species of Flax (order Linaceæ) are to be found on chalky soils. One--the Perennial Flax (Linum perenne)--grows in hilly districts, but is not at all common. It is a slender plant, with numerous wiry stems from one to two feet high; and sessile, linear, acute leaves. The petals are of a beautiful sky-blue colour, but so lightly attached that it is difficult to secure a perfect specimen. The other species--the Narrow-leaved Flax (L. angustifolium)--is moderately common on calcareous hills of the South and West of England. It is very similar to the last, and grows to about the same height, but its many stems are more irregularly branched, and the alternate leaves are linear-lanceolate. The corolla is of a lighter lilac-blue colour. L. perenne blooms during June and July, and the narrow-leaved species from June to September. The latter is shown on Plate VIII.

Quite a number of species of leguminous plants (order Leguminosæ), may, as a rule, be met with on dry soils, but only two common ones may be described as particularly partial to chalk and limestone localities. These are the Tufted Horse-shoe Vetch (Hippocrepis comosa) and the Sainfoin or Cock's-head (Onobrychis sativa). The former, represented on Plate VIII, is a low, smooth, prostrate plant, six to eighteen inches long, with yellow flowers that bloom from May to August. This plant is sometimes confused with the Bird's-foot Trefoil, which it rather closely resembles in general appearance, but it may be readily distinguished by the pinnate leaves and the peculiar form of the pods. The latter are flattened, and break up, when ripe, into from three to six one-seeded, horse-shoe-shaped segments--a feature which has given rise to the popular name.

The Sainfoin is often cultivated in the South-East of England as fodder for cattle, but may frequently be found growing wild. It is a very pretty, erect plant, from one to two feet high, with dense racemes of rosy-red flowers beautifully striped with a darker tint. The stem is stout and downy, and the pinnate leaves have membranous stipules and numerous oblong leaflets which terminate abruptly in a point. The pod is compressed, semicircular in form, indehiscent, and toothed along the lower edge. This species flowers during June and July.

On some chalky heaths the True Sweet-briar (Rosa rubiginosa--order Rosaceæ) is a common shrub, growing from three to six feet high, and flowering during June and July. It is an erect and compact bush, with numerous prickles of varying shapes--the larger ones being hooked, while the smaller are straight and very unequal. The leaves are compound and stipuled, and the leaflets are rounded at the base, downy, and doubly serrate. The flowers often grow singly, but more commonly from two to four together; they are of a deep rose colour, and the persistent sepals are pinnately divided. The fruit is at first pear-shaped, but afterwards becomes almost globular, and turns red when ripe.

In similar situations we may find the Lesser Burnet or Salad Burnet (Poterium Sanguisorba) of the same order. This plant is so different in general appearance from the majority of the Rose family that the amateur would hardly associate it with the others. The flowers are small, and collected together in dense, purple cymes on the top of long, angular stalks. They have no petals, and the four overlapping sepals are usually deciduous. The stamens, five to thirty in number, are pendulous on long, slender filaments; and the upper flowers display their crimson stigmas before the lower ones produce their stamens. The stem is erect, from six to eighteen inches in height; and the pinnate leaves have many small, sessile, oblong leaflets with coarsely-serrate edges. This plant flowers during June, July, and August.

The Bedstraw Family (order Rubiaceæ) is represented on the chalk by the Rough-fruited Corn Bedstraw (Galium tricorne), which is common in fields. It is a spreading plant, with procumbent stems, one to three feet long; and small, long, narrow leaves, rough with recurved prickles, arranged in whorls of from six to eight. The flowers are small and white, grouped in little cymes of three. The fruit is comparatively large, and granulated, but not bristly, and it droops by the bending of the pedicel. The plant flowers from June to October.

The Red Spur Valerian (Centranthus ruber--order Valerianaceæ) is a glaucous, leafy plant (see Plate VIII), sometimes growing to a height of two feet or more, often to be seen in chalk-pits and limestone quarries, and frequently on old walls. It is not indigenous, but is cultivated largely as a garden flower, and has now become naturalised. Its corolla, which is sometimes white, has five unequal lobes, a long, flattened tube, and a slender spur. The plant flowers from June to September.

Of the Composite flowers we shall note two species, the first being the Woolly-headed Plume-thistle (Carduus eriophorus), common in chalky fields, where it throws up its large, cottony heads to a height of from three to five feet during July and August. In order to distinguish it from other similar thistles we must note that its stem is not winged, and that the deeply-divided leaves, with bifid lobes, half clasp the stem at the base; also that the involucre bracts are lanceolate, with long, reflexed spines. The heads of this thistle are of a pale purple colour, of a globular form, two to three inches in diameter, and covered with a thick, cottony growth.

Our other example of the Composite flowers is the Ploughman's Spikenard (Inula Conyza), which is common on chalky banks and pastures, flowering from July to September. It is an erect, downy plant, from two to five feet high, with oval, lanceolate, downy leaves of a dull green colour. The upper leaves are entire and sessile, while the lower are toothed and stalked. The numerous flower heads are of a dull yellow colour, with leaflike bracts, arranged in a branched corymb. The involucre bracts are linear and reflexed, and the ray florets are inconspicuous.

Two representatives of the order Gentianaceæ are commonly found on chalk hills and pastures; they are the Field Gentian (Gentiana campestris), and the Perfoliate Yellow-wort (Chlora perfoliata, or Blackstonia perfoliata). The former is an erect plant, from four to ten inches high, with a branched stem; opposite, sessile leaves; and conspicuous, bluish-purple flowers, blooming in August and September. The calyx is cleft into four, the two outer segments being large and ovate. The corolla is also four-cleft, and salver-shaped.

The Yellow-wort is an erect, glaucous plant, with an unbranched stem from six to eighteen inches in height, and beautiful yellow flowers, from four to nine in number, arranged in a cyme. The leaves are in widely-separated pairs, united at their bases, so that the stem penetrates them. The calyx is deeply divided, and the limbs of the corolla are spreading. This plant flowers from June to September.

Some species of Mullein (Verbascum) are particularly partial to chalk and limestone districts. They are handsome plants, belonging to the order Scrophulariaceæ, rendered conspicuous by their woolly leaves and spikes of yellow or white flowers. The Great Mullein (V. Thapsus) is common on banks and roadsides, and flowers from June to August. Its stem is stout, erect, very woolly, and varies from two to five feet in height. The leaves are very large and thick, and are so woolly on both sides that they resemble flannel. The flowers form a large, dense, club-shaped spike. Each has a corolla with five spreading lobes; and five stamens, with white hairs on their filaments, two longer than the other three. The fruit is a capsule containing many seeds and splitting longitudinally.