ON BIO-GEOLOGY ¹

I am not sure that the subject of my address is rightly chosen.  I am not sure that I ought not to have postponed a question of mere natural history, to speak to you as scientific men, on the questions of life and death, which have been forced upon us by the awful warning of an illustrious personage’s illness; of preventible disease, its frightful prevalency; of the 200,000 persons who are said to have died of fever alone since the Prince Consort’s death, ten years ago; of the remedies; of drainage; of sewage disinfection and utilisation; and of the assistance which you, as a body of scientific men, can give to any effort towards saving the lives and health of our fellow-citizens from those unseen poisons which lurk like wild beasts couched in the jungle, ready to spring at any moment on the unsuspecting, the innocent, the helpless.  Of all this I longed to speak; but I thought it best only to hint at it, and leave the question to your common sense and your humanity; taking for granted that your minds, like the minds of all right-minded Englishmen, have been of late painfully awakened to its importance.  It seemed to me almost an impertinence to say more in a city of whose local circumstances I know little or nothing.  As an old sanitary reformer, practical, as well as theoretical, I am but too well aware of the difficulties which beset any complete scheme of drainage, especially in an ancient city like this; where men are paying the penalty of their predecessors’ ignorance; and dwelling, whether they choose or not, over fifteen centuries of accumulated dirt.

And, therefore, taking for granted that there is energy and intellect enough in Winchester to conquer these difficulties in due time, I go on to ask you to consider, for a time, a subject which is growing more and more important and interesting, a subject the study of which will do much towards raising the field naturalist from a mere collector of specimens—as he was twenty years ago—to a philosopher elucidating some of the grandest problems.  I mean the infant science of Bio-geology—the science which treats of the distribution of plants and animals over the globe, and the cause of that distribution.

I doubt not that there are many here who know far more about the subject than I; who are far better read than I am in the works of Forbes, Darwin, Wallace, Hooker, Moritz Wagner, and the other illustrious men who have written on it.  But I may, perhaps, give a few hints which will be of use to the younger members of this Society, and will point out to them how to get a new relish for the pursuit of field science.

Bio-geology, then, begins with asking every plant or animal you meet, large or small, not merely—What is your name?  That is the collector and classifier’s duty; and a most necessary duty it is, and one to be performed with the most conscientious patience and accuracy, so that a sound foundation may be built for future speculations.  But young naturalists should act not merely as Nature’s registrars and census-takers, but as her policemen and gamekeepers; and ask everything they meet—How did you get there?  By what road did you come?  What was your last place of abode?  And now you are here, how do you get your living?  Are you and your children thriving, like decent people who can take care of themselves, or growing pauperised and degraded, and dying out?  Not that we have a fear of your becoming a dangerous class.  Madame Nature allows no dangerous classes, in the modern sense.  She has, doubtless for some wise reason, no mercy for the weak.  She rewards each organism according to its works; and if anything grows too weak or stupid to take care of itself, she gives it its due deserts by letting it die and disappear.  So, you plant or you animal, are you among the strong, the successful, the multiplying, the colonising?  Or are you among the weak, the failing, the dwindling, the doomed?

These questions may seem somewhat rude: but you may comfort yourself by the thought that plants and animals, though they deserve all kindness, all admiration, deserve no courtesy—at least in this respect.  For they are, one and all, wherever you find them, vagrants and landlopers, intruders and conquerors, who have got where they happen to be simply by the law of the strongest—generally not without a little robbery and murder.  They have no right save that of possession; the same by which the puffin turns out the old rabbits, eats the young ones, and then lays her eggs in the rabbit-burrow—simply because she can.

Now, you will see at once that such a course of questioning will call out a great many curious and interesting answers, if you can only get the things to tell you their story; as you always may if you will cross-examine them long enough; and will lead you into many subjects beside mere botany or entomology.  So various, indeed, are the subjects which you will thus start, that I can only hint at them now in the most cursory fashion.

At the outset you will soon find yourself involved in chemical and meteorological questions; as, for instance, when you ask—How is it that I find one flora on the sea-shore, another on the sandstone, another on the chalk, and another on the peat-making gravelly strata?  The usual answer would be, I presume—if we could work it out by twenty years’ experiment, such as Mr. Lawes, of Rothampsted, has been making on the growth of grasses and leguminous plants in different soils and under different manures—the usual answer, I say, would be—Because we plants want such and such mineral constituents in our woody fibre; again, because we want a certain amount of moisture at a certain period of the year: or, perhaps, simply because the mechanical arrangement of the particles of a certain soil happens to suit the shape of our roots and of their stomata.  Sometimes you will get an answer quickly enough; sometimes not.  If you ask, for instance, Asplenium viride how it contrives to grow plentifully in the Craven of Yorkshire down to 600 or 800 feet above the sea, while in Snowdon it dislikes growing lower than 2000 feet, and is not plentiful even there?—it will reply—Because in the Craven I can get as much carbonic acid as I want from the decomposing limestone; while on the Snowdon Silurian I get very little; and I have to make it up by clinging to the mountain tops, for the sake of the greater rainfall.  But if you ask Polypodium calcareum—How is it you choose only to grow on limestone, while Polypodium Dryopteris, of which, I suspect, you are only a variety, is ready to grow anywhere?—Polypodium calcareum will refuse, as yet, to answer a word.

Again—I can only give you the merest string of hints—you will find in your questionings that many plants and animals have no reason at all to show why they should be in one place and not in another, save the very sound reason for the latter which was suggested to me once by a great naturalist.  I was asking—Why don’t I find such and such a species in my parish, while it is plentiful a few miles off in exactly the same soil?—and he answered—For the same reason that you are not in America.  Because you have not got there.  Which answer threw to me a flood of light on this whole science.  Things are often where they are, simply because they happen to have got there, and not elsewhere.  But they must have got there by some means, and those means I want young naturalists to discover; at least, to guess at.

A species, for instance—and I suspect it is a common case with insects—may abound in a single spot, simply because, long years ago, a single brood of eggs happened to hatch at a time when eggs of other species, who would have competed against them for food, did not hatch; and they may remain confined to that spot, though there is plenty of food for them outside it, simply because they do not increase fast enough to require to spread out in search of more food.  Thus I should explain a case which I heard of lately of Anthocera trifolii, abundant for years in one corner of a certain field, and only there; while there was just as much trefoil all round for its larvæ as there was in the selected spot.  I can, I say, only give hints: but they will suffice, I hope, to show the path of thought into which I want young naturalists to turn their minds.

Or, again, you will have to inquire whether the species has not been prevented from spreading by some natural barrier.  Mr. Wallace, whom you all of course know, has shown in his “Malay Archipelago” that a strait of deep sea can act as such a barrier between species.  Moritz Wagner has shown that, in the case of insects, a moderately-broad river may divide two closely-allied species of beetles, or a very narrow snow-range, two closely-allied species of moths.

Again, another cause, and a most common one, is: that the plants cannot spread because they find the ground beyond them already occupied by other plants, who will not tolerate a fresh mouth, having only just enough to feed themselves.  Take the case of Saxifraga hypnoides and S. umbrosa, “London pride.”  They are two especially strong species.  They show that, S. hypnoides especially, by their power of sporting, of diverging into varieties; they show it equally by their power of thriving anywhere, if they can only get there.  They will grow both in my sandy garden, under a rainfall of only 23 inches, more luxuriantly than in their native mountains under a rainfall of 50 or 60 inches.  Then how is it that S. hypnoides cannot get down off the mountains; and that S. umbrosa, though in Kerry it has got off the mountains and down to the sea-level, exterminating, I suspect, many species in its progress, yet cannot get across County Cork?  The only answer is, I believe, that both species are continually trying to go ahead; but that the other plants already in front of them are too strong for them, and massacre their infants as soon as born.

And this brings us to another curious question: the sudden and abundant appearance of plants, like the foxglove and Epilobium angustifolium, in spots where they have never been seen before.  Are there seeds, as some think, dormant in the ground; or are the seeds which have germinated, fresh ones wafted thither by wind or otherwise, and only able to germinate in that one spot because there the soil is clear?  General Monro, now famous for his unequalled memoir on the bamboos, holds to the latter theory.  He pointed out to me that the Epilobium seeds, being feathered could travel with the wind; that the plant always made its appearance first on new banks, landslips, clearings, where it had nothing to compete against; and that the foxglove did the same.  True, and most painfully true, in the case of thistles and groundsels: but foxglove seeds, though minute, would hardly be carried by the wind any more than those of the white clover, which comes up so abundantly in drained fens.  Adhuc sub judice lis est, and I wish some young naturalists would work carefully at the solution; by experiment, which is the most sure way to find out anything.

But in researches in this direction they will find puzzles enough.  I will give them one which I shall be most thankful to hear they have solved within the next seven years—How is it that we find certain plants, namely, the thrift and the scurvy grass, abundant on the sea-shore and common on certain mountain-tops, but nowhere between the two?  Answer me that.  For I have looked at the fact for years—before, behind, sideways, upside down, and inside out—and I cannot understand it.

But all these questions, and especially, I suspect, that last one, ought to lead the young student up to the great and complex question—How were these islands re-peopled with plants and animals, after the long and wholesale catastrophe of the glacial epoch?

I presume you all know, and will agree, that the whole of these islands, north of the Thames, save certain ice-clad mountain-tops, were buried for long ages under an icy sea.  From whence did vegetable and animal life crawl back to the land, as it rose again; and cover its mantle of glacial drift with fresh life and verdure?

Now let me give you a few prolegomena on this matter.  You must study the plants of course, species by species.  Take Watson’s “Cybele Britannica” and Moore’s “Cybele Hibernica;” and let—as Mr. Matthew Arnold would say—“your thought play freely about them.”  Look carefully, too, in the case of each species, at the note on its distribution, which you will find appended in Bentham’s “Handbook,” and in Hooker’s “Student’s Flora.”  Get all the help you can, if you wish to work the subject out, from foreign botanists, both European and American; and I think that, on the whole, you will come to some such theory as this for a general starling platform.  We do not owe our flora—I must keep to the flora just now—to so many different regions, or types, as Mr. Watson conceives, but to three, namely, an European or Germanic flora, from the south-east; an Atlantic flora, from the south-east; a Northern flora, from the north.  These three invaded us after the glacial epoch; and our general flora is their result.

But this will cause you much trouble.  Before you go a step farther you will have to eliminate from all your calculations most of the plants which Watson calls glareal, i.e. found in cultivated ground about habitations.  And what their limit may be I think we never shall know.  But of this we may be sure; that just as invading armies always bring with them, in forage or otherwise, some plants from their own country—just as the Cossacks, in 1815, brought more than one Russian plant through Germany into France—just as you have already a crop of North German plants upon the battle-fields of France—thus do conquering races bring new plants.  The Romans, during their 300 or 400 years of occupation and civilisation, must have brought more species, I believe, than I dare mention.  I suspect them of having brought, not merely the common hedge elm of the south, not merely the three species of nettle, but all our red poppies, and a great number of the weeds which are common in our cornfields; and when we add to them the plants which may have been brought by returning crusaders and pilgrims; by monks from every part of Europe, by Flemings or other dealers in foreign wool—we have to cut a huge cantle out of our indigenous flora: only, having no records, we hardly know where and what to cut out; and can only, we elder ones, recommend the subject to the notice of the younger botanists, that they may work it out after our work is done.

Of course these plants introduced by man, if they are cut out, must be cut out of only one of the floras, namely, the European; for they, probably, came from the south-east, by whatever means they came.

That European flora invaded us, I presume, immediately after the glacial epoch, at a time when France and England were united, and the German Ocean a mere network of rivers, which emptied into the deep sea between Scotland and Scandinavia.  And here I must add, that endless questions of interest will arise to those who will study, not merely the invasion of that truly European flora, but the invasion of reptiles, insects, and birds, especially birds of passage, which must have followed it as soon as the land was sufficiently covered with vegetation to support life.  Whole volumes remain to be written on this subject.  I trust that some of your younger members may live to write one of them.  The way to begin will be; to compare the flora and fauna of this part of England very carefully with that of the southern and eastern counties; and then to compare them again with the fauna and flora of France, Belgium, and Holland.

As for the Atlantic flora, you will have to decide for yourselves whether you accept or not the theory of a sunken Atlantic continent.  I confess that all objections to that theory, however astounding it may seem, are outweighed in my mind by a host of facts which I can explain by no other theory.  But you must judge for yourselves; and to do so you must study carefully the distribution of heaths both in Europe and at the Cape, and their non-appearance beyond the Ural Mountains, and in America, save in Labrador, where the common ling, an older and less specialised form, exists.  You must consider, too, the plants common to the Azores, Portugal, the West of England, Ireland, and the Western Hebrides.  In so doing young naturalists will at least find proofs of a change in the distribution of land and water, which will utterly astound them when they face it for the first time.

As for the Northern flora, the question whence it came is puzzling enough.  It seems difficult to conceive how any plants could have survived when Scotland was an archipelago in the same ice-covered condition as Greenland is now; and we have no proof that there existed after the glacial epoch any northern continent from which the plants and animals could have come back to us.  The species of plants and animals common to Britain, Scandinavia, and North America, must have spread in pre-glacial times when a continent joining them did exist.

But some light has been thrown on this question by an article, as charming as it is able, on “The Physics of the Arctic Ice,” by Dr. Brown of Campster.  You will find it in the “Quarterly Journal of the Geological Society” for February, 1870.  He shows there that even in Greenland peaks and crags are left free enough from ice to support a vegetation of between three hundred or four hundred species of flowering plants; and, therefore, he well says, we must be careful to avoid concluding that the plant and animal life on the dreary shores or mountain-tops of the old glacial Scotland was poor.  The same would hold good of our mountains; and, if so, we may look with respect, even awe, on the Alpine plants of Wales, Scotland, and the Lake mountains, as organisms, stunted it may be, and even degraded by their long battle with the elements, but venerable from their age, historic from their endurance.  Relics of an older temperate world, they have lived through thousands of centuries of frost and fog, to sun themselves in a temperate climate once more.  I can never pick one of them without a tinge of shame; and to exterminate one of them is to destroy, for the mere pleasure of collecting, the last of a family which God has taken the trouble to preserve for thousands of centuries.

I trust that these hints—for I can call them nothing more—will at least awaken any young naturalist who has hitherto only collected natural objects, to study the really important and interesting question—How did these things get here?