British flora

“ Before setting about discussing the various types of vegetation which our own country presents, it will be well to have a general idea of the extent to which the main types are developed, and of the amount to which agriculture has interfered with the native flora. We have seen that the natural vegetation of the greater part of the British Isles is woodland: yet so profoundly has human industry altered the face of the country that woodland, natural or planted, occupies only about one-twentieth of the surface of England, rather less of Scotland and Wales, and about one-seventieth of Ireland. ”

“ Though our country’s vegetation has lost in scientific interest, it has gained vastly in both economic and æsthetic value by the introduction of useful and ornamental plants from all the Temperate regions of the world; and besides, a large number of species have followed in man’s footsteps, and, taking advantage of the disturbance of the native flora caused by his operations, endeavour with more or less success to establish a footing in the country. ”

“ By following up the clue supplied by the floating seed, we have arrived at the conclusion with respect to the British flora that plants with buoyant seeds or fruits gather at the water-side. But we have yet to inquire why some of these plants are “located” at the sea-coast and others on the borders of ponds and rivers. Mere buoyancy aided by chance has not determined the choice. There are definite principles at work in the economy of plant-life that make the selection for each plant. ”

“ PREFACE In the following chapters an attempt is made to deal, in a quite elementary way, with some of the wider aspects of plant life—to discuss questions which arise in the mind from a contemplation of the vegetation which clothes with a green mantle the surface of our own country. No essay is made to enumerate or define the plants to be met with in the different types of ground, or in the different geographical areas, which go to make up the British Isles: there are already plenty of excellent handbooks and local floras in which that aspect of native plant life is treated. ”

“ Within any one climatic region—say within the British Islands—the soil in which the plants grow is the controlling factor in determining the character of the plant population. And while a classification by plant form—such as woodland, grassland—is often convenient, when we come to analyze the various plant associations which colonize the ground, it will be found that similarity of form-type does not necessarily imply affinity as regards either physiological conditions or floristic constituents. ”

“ Assiminea grayana. Thames Estuary. Peculiarities of the British Flora.—Thinking it probable that there must also be some peculiar British plants, but not finding any enumeration of such in the British Floras of Babington, Hooker, or Bentham, I applied to the greatest living authority on the distribution of British plants—the late Mr. H. C. Watson, who very kindly gave me the information I required, and I cannot do better than quote his words: "It may be stated pretty confidently that there is no 'species' (generally accepted among botanists as a good species) peculiar to the British Isles. ”

“ From Tertiary strata in the Isle of Wight, on the Hampshire coast, and in the London basin numerous fossil plants have been obtained, which afford convincing evidence of climatic conditions much more genial than those of the present day. The presence of palm leaves and of a wealth of other sub-tropical plants in Lower Tertiary beds in England reveals the existence of a flora differing considerably both from that in the uppermost Tertiary beds of Norfolk and from the modern British flora, but closely allied to the present Mediterranean flora. ”

“ And now, just as a point is reached when at length we think we shall see our present British flora emerging fully from the obscurity of the ages, a dramatic interruption occurs, which confuses the record and brings us into difficulties of many sorts, giving rise to controversies which are still far from being settled. The climate becomes suddenly colder, and Europe is plunged into the rigours of the Ice Age. ”

“ Although the world offers many different aspects of closed vegetation, they may all in a broad sense be reduced to two general types—namely, grasslands and woodlands, the former the result of a lighter, the latter of a heavier, rainfall: grasses and their associates requiring for their life-processes a much less amount of water than a tree vegetation. The British Isles lie within a broad belt that sweeps east and west across Europe, characterized by a prevalence of south-west winds laden with moisture, and yielding a tolerably heavy rainfall distributed throughout the year. ”

“ The question of the Lusitanian and American elements in our flora has been treated at some length both because it offers one of the most interesting problems in British botany, and because it affords a good illustration of the far-reaching nature of the questions which may lie behind the occurrence on our hills or in our valleys of even the humblest plant or animal. Each organism has a long record behind it, stretching far beyond the earliest periods of human history ”

“ The Illustrated British Flora, a Description (with a Wood-Engraving, including dissections, of each species) of the Flowering Plants and Ferns indigenous to, or naturalized in, the British Isles. By George Bentham, F.R.S., President of the Linnæan Society. Demy 8vo, 2 vols., 1295 Wood-Engravings, from Original Drawings by W. Fitch, £3 10s. ”

“ If we let the eye sweep round the horizon, we note a similar contrast displayed on broader lines. On the one hand is the mountain-land, with its carpet of grass and heather extending to the very summits; on the other hand the broad expanses of bare sand and mud fringing Morecambe Bay, apparently devoid of any vegetation. And it occurs to us that, before we ponder over the variety and distribution of plant life on this world, we are faced at once with a more profound problem. ”

“ It will be seen how little of the original vegetation of England is left to us for purposes of study—less than one-fifth, almost the whole of which has been influenced to some degree by human operations; while in Scotland and Ireland a much larger area is more or less in its primitive condition. ”

“ The British Isles are geographically and biologically by no means a separate area, and they have derived their population, both plant and animal, by immigration at various periods of time from the great land area to the eastward. Our present flora proves the truth of this as a general assertion; a study of its constituents shows that it is essentially a reduced continental European flora. As we step from France across to England we lose a number of plants familiar on the French side. As we step again from England into Ireland a further number of plants disappears ”

“ The Scottish mountain-sides and Irish moorlands still to a great extent retain a natural flora, save that the greater number of grazing animals which they now support, as compared with the times when wolves and other enemies roamed unchecked, leaves its impress upon the vegetation.
Viewing the plant world as a whole, its primary divisions, from the point of view of ecology, are governed by the factor of rainfall. It is true that the plants of the Tropics differ profoundly from those of the Temperate regions, and those again from the plants of the Arctic. ”

“ The Seed Plants, then, achieved their wonderful abundance and variety owing to the highly stimulating conditions offered by a terrestrial existence; we must assign to all the existing types a long terrestrial ancestry. How, then, about the water plants whose leaves and flowers so decorate our lakes? There seems no doubt [13] that they are species which have left the land to resume the aquatic habits of their remote ancestors. With few exceptions they retain the aerial mode of pollination which is the pride of the specialized land plants. ”

“ Those species whose aboriginal distribution stopped short of the western limit of the land had no doubt a fluctuating western or northern or southern boundary to their range, dependent on temporary conditions. Thus, a hard winter might kill back a plant already at the limit of its natural range, or a warm summer, by ripening abundance of its seed, might result in its slight advance. ”

“ Viewing generally the migration of the Seed Plants from land to water, we see that the fresh waters of the world, untenanted by other large plants, have been{207} fully colonized, generally a long time ago, and by plants of rather early types. But as regards the sea, the luxuriant Algal vegetation which is in possession of our shores has no reason to tremble for its supremacy. ”

“ The flora of harbours and docksides is often as cosmopolitan as the sailors of the ships by whose agency it came there; and the unfamiliar weeds—the gipsies and tramps of the plant world—which we encounter on roadsides, rubbish-heaps, and railway stations lend an additional interest to our botanical rambles.
Turning now to the plants which are used by man, it may be pointed out in the first place that the human race obtains much more, whether of profit or of{146} pleasure, from the vegetable than from the animal kingdom. Flesh, whether derived from mammals, birds, or fishes ”

“ Although our own country, favoured by conditions thoroughly suitable to plant life—a sufficiently high temperature and an abundance of moisture and light—is characterized by a continuous plant mantle—or closed vegetation, as the botanists say—nevertheless what has been said of desert and semi-desert conditions applies to many limited areas in the British Isles, where the vegetation takes on the peculiar characters of true desert plants. Low water-content and great exposure produce such conditions on shingle beaches and sand dunes ”

“ While a wild grass growing in Palestine has been quite recently identified as the probable source of the Hard Wheats, the native parent of the Soft Wheats is unknown. That productiveness has in all cases been much increased by long selection there can be no doubt; it may be pointed out that several species of Triticum, Hordeum, and Avena, allies of the Wheat, Barley, and Oat, are included in the native British flora, but they are useless as producers of grain.
Nowhere is the effect on plants of selection and cultivation seen better than in our native fruit-trees. ”

“ Nowadays, the number of species cultivated, the innumerable forms of these which are grown, and the wide distribution{149} which these forms have attained, have resulted in the cultivated flora of a country like England being, so far as the higher plants are concerned, much larger than the native flora, even when all the plants which are grown under glass are left out of consideration. ”

“ Before we trespass on the domains of arboriculture, horticulture, or agriculture, under which heads the cultivation of useful or ornamental plants divides itself, some consideration is required of those plants which, quasi-wild, are usually included in accounts of the vegetation under the head of aliens, denizens, colonists, and so forth. ”

“ Once more, we have already from Farleton Fell observed that plants do not grow higgledy-piggledy over the country, but are arranged in more or less definite societies depending on similarity of climate, soil, and other external conditions. Studied from this point of view, the flora resolves itself into a series of communities, each requiring a certain set of conditions for its continued welfare. ”

“ In garden flowers, also, we see most striking results of continuous selection. By taking advantage of the tendency of stamens and carpels to change occasionally into petals, and of petals to increase in number, “double flowers” have been effected. When “doubling” is complete—that is, when the conversion into petals is thorough—no seed can of course be produced, and the plants must be propagated by cuttings. Different other slight natural variations, exaggerated by selection and cultivation, have been the source of innumerable “varieties” in our gardens. ”

“ The great majority of water plants send their flowers up above the surface to be pollinated by wind or (more rarely) by insects. It may be noted that few of the more highly evolved groups of Seed{201} Plants are represented in the aquatic flora; wind-pollinated flowers of a rather primitive type of structure are the rule in our lakes and rivers; which points to an early assumption of the aquatic habit, and suggests that the land is more favourable than the water for the evolution of higher types. ”

“ But as much of this favourable region is utilized by the human race for the production of plants used for food or for industry, it often happens, as in our own country, that the natural plant communities are to a great extent destroyed, and can be studied only on{25} land left undisturbed because unsuitable for cultivation—on heaths and moors, in swamps and lakes, on sea-sands, chalk downs, and so on ”

“ Our own mountains are not lofty; nowhere in the British Islands is a height of a mile attained. But we have only to ascend to a couple of thousand feet to note a great change in the vegetation. The plants of the lower grounds to a great extent die out (though some accompany us to our highest summit) , and the vegetation takes on a low compact form, which becomes more emphasized as we ascend farther, till in sheltered nooks alone do we find any plants more than a few inches in height. ”