BRITISH WILD FLOWERS.*

Sin Jons LUBBOCK informs us in his preface that this little book has grown out of observations and notes, originally prepared: "with the view of encouraging in my children that love of naturar history from which I myself have derived so much happiness.' Even apart from such an object, a very considerable value might be claimed for studies of this kind as a mere intellectual exercise. But. stillfurther, Sir John Lubbock's graceful exposition gives us, for the- first time in this country, a brief but comprehensive view of the- result of applying the principle of natural selection to a large class-- of biological phenomena which hitherto, till Mr. Darwin calla attention to them, had hardly seemed even a possible field for- scientific explanation.

In 1787 Conrad Sprengel noticed in the flowers of Geranium, sylcaticum—one of the most beautiful of the indigenous plants of* Northern Europe—mi number of delicate hairs. Confined that. the "wise Author of Nature would not have created even a hair' in vain," he endeavoured to ascertain the use of these hairs, and. satisfied himself that they served to protect the honey from rain.. This observation was the starting-point of what may be calledi floral teleology. He studied the structure of numerous other. flowers with great care, and found the key to the singularities and.

• On British Wild Flowers Considered in Relation to Insects By Sir John Lubbock,. Bart., F.11.S., M.P. London : Macmain.

complexities of their architecture in their adaptation to the visits

of insects.

The vast majority of flowers contain, besides the structures (the pistil) which enclose the rudimentary seeds, others (the stamens) which produce that dust-like substance familiar to most persons under its technical name of "pollen." The function of pollen, dimly appreciated as early as the time of Pliny, was more specifi- cally pointed out by Sir Thomas Millington in 1676. It is a matter pretty well known, at any rate to those who have at any time had concern with gardens, that without the application of pollen to the pistil the rudimentary seeds never mature. It might perhaps seem a tolerably safe inference, that inasmuch as a natural provision

has placed within the envelopes of the same flower, in the vast ma- jority of cases, both the stamens and pistil—i.e., the pollen and seed- producing structures—the former were intended to influence the

latter, so as to provide by close proximity for the least possible risk of failure in the process of fertilisation. What, however, Sprengel discovered was that in an immense number of cases the practical results of this conjunction were in one way or other carefully defeated. One very common mode in which this happens is when the stamens and pistil do not ripen at the same time. For example, in the Pink, in its first condition, the stamens are mature and project above the flat top or disc of the flower, while the whole of the pistil is concealed within the tube. In a later stage of the same flower, the stamens have shrivelled up, disappeared, and the apices of the pistil ready for the reception of pollen, are protruded in their place. It is quite clear that in a case like this, without some external assistance, the pink will bloom quite fruitlessly. Now, this assistance is provided by the visits of insects. At the bottom of the tube of the flower a secretion of honey takes place. The flat top formed by the spreading petals forms a convenient alighting-place for flies which come to feed on the pollen, and for butterflies which reach the honey with their long proboscis. If the stamens are protruded from the flower, the insect will certainly bedaub itself with the pollen, and as such insects habitually range from flower to flower, it is quite clear that sooner or later, the pollen of one blossom will be conveyed to the pistil of another. Now, the question at once arises why nature should prefer this circuitous cross-fertilisation to self-fertilisation, which would apparently be so much simpler. And the answer which must be made is, that it is an advantage to the plants that it should be so preferred. Sir John Lubbock sums up our knowledge on this point to the following effect :—

" I will not now enter on the large question why this cross-fertilisa- tion should be an advantage; but that it is has been clearly proved. Kolrenter speaks with astonishment of the sfatura portentosa' of some plants thus raised by him ; indeed, says Mr. Darwin, all experimenters have been struck with the wonderful vigour, height, tenacity of life, precocity, and hardiness of their hybrid productions. Mr. Darwin himself, however, was, I believe, the first to show that if a flower be fertilised by pollen from a different plant, the seedlings so produced are much stronger than if the plant be fertilised by its own pollen. I have had the advantage of seeing several of these experiments, and the difference is certainly most striking. For instance, six crossed and six self-fertilised seeds of lpomma purpurea were grown in pairs on opposite aides of the same pots ; the former reached a height of seven feet, while the others were, on an average, only five feet four inches. The first also flowered more profusely. It is, moreover, remarkable that in many eases plants are themselves more fertile if supplied with pollen from a different flower, a different variety, or even, as it would appear in some instances (in the passion-flower, for instance), from a different species. Nay, in some cases pollen has no effect what- ever unless transferred to a different flower. Fritz Miiller has recorded some species in which pollen, if placed on the stigma of ill() same flower, has not only no more effect than so much inorganic dust; but, which is perhaps even more extraordinary, in others, he states that the pollen placed on the stigma of its own flower acted on it like a poison.' (pp. 6 and 7.)

We are very soon, therefore, brought face to face with the fact that all that strikes us as admirable and pleasing in the varied forms, tints, odours, and even modes of opening and shutting of flowers, have reference to the transference of pollen from one flower to another by the intervention (in the majority of cases) of insects. And besides this strictly teleological way of interpreting floral structure, we are asked to accept the conclusion that all the wonderful contrivances, with the detailed mechanism of which every page of this book is filled, arose gradually from the operation of the principle of the "sur- vival of the fittest" ; those arrangements which most favoured the substitution of cross-fertilisation for self-fertilisation—once, probably, common to all flowers—giving rise to the strongest and most fruitful races, which being strongest and most fruitful, in the long run have survived.

The necessity of the visits of insects to flowers was, as has been said, first clearly made out by Sprengel. His observations were published in 1793, in a copiously illustrated work, to which he gave the name, " Das Entdeckte Geheimniss der Natur." For a long time the result of his labours attracted little attention. Sir- John Lubbock points out the reason for this. Sprengel assumed that the varied structure of flowers, which in so many cases inhibits self-fertilisation, was a kind of ultimate fact. Plants, then, being placed in this predicament, for reasons which he would have regarded as hopeless, if not irreverent, to attempt to fathom, the visits of insects were arranged mainly in order to overcome the difficulty. But the shape in which the facts are presented by Sprengel is wanting in interest and rationality. The true source of pleasure in scientific study is in apprehending the comparative capacity of the successive hypotheses which are presented to us to explain phenomena. Now, important

as Sprengel's results were, they were very soon evacuated of interest. On the one hand, he shows us a set of arrangements precluding self-fertilisation, for which prima facie flowers would

have seemed to be specially designed ; on the other, he shows us a set of arrangements remedying the disabilities. But as to the why and wherefore, we must be content to fall back on the decrees of the " sapientissimus rerum Opifex." Logically this is- a sufficient explanation, but it is not. an intellectually gratifying one. Sir John Lubbock complains that,—

" While Sprengel's deep religious feeling thus gave him the clue which has thrown so much light on the origin and structure of flowers, the- comparatively low conception of creative power which was in his time, and indeed until recently prevalent, led him to assume that each flower- was created as we now see it, and prevented him from perceiving the real significance of the facts which he had discovered, while the true evplanation could scarcely have escaped him if he had possessed that higher view of creation which we owe to Mr. Darwin."

Now Sprengel's discoveries fell for a time into oblivion, because at the best they were then only curious ; they had not yet become significant ; they were apt adornments for a Bridgewater treatise, and that was all. But is Sir John Lubbock right in blaming either Sprengel or his time for this? It seems to us hardly so. Sprengel seems to have gone as far as he could go with his facts, and it is in its way a noteworthy thing that a man should be led by deep religious feeling to supply the material for one of the most important chapters in. the Origin of Species. But he could not go further, in ignorance of the generalisation "that it is a law of nature that organic beings shall not fertilise themselves for perpetuity." Now his- torically this was not arrived at till after his labours were com- pleted. And we cannot doubt that when, in 1799, Andrew Knight enunciated it, he really extended to the vegetable kingdom a prin- ciple which was drawn from the consideration of what is advanta- geous amongst animals. Mr. Darwin remarks of Sprengel that he " failed to understand the full meaning of the structure of the flowers. which he has so well described, from not always having before his mind the key to the problem, namely, the good derived from the crossing of distinct individual plants." This key it was difficult for a man reflecting merely on the facts of vegetable life to obtain. On the other hand, to a naturalist like Andrew Knight, who ex- perimented on the breeding of horses as well as of peas, it was extremely likely to suggest itself prominently. If Sprengel had worked at the beginning of this century rather than at the end of the last, it may be doubted whether his low conception of creative power would have hindered his. pushing his teleology perhaps almost as far as Sir John Lub- bock has done. But the lot of Sprengel is common enough in scientific research. Facts and observations are chiefly valuable when taken in connection with other facts and observations. It is the relations between them rather than the facts themselves. that are intellectually important. If a discoverer is in advance of his day, and comes upon a new point which will not fit in. with the current state of his science, he must be content to, wait,—its time will come, though not perhaps in his own day.

There is no side from which the doctrine of the progressive evolution of organic beings can be approached so dispassionately as that which is afforded by the study of plants. Every horti- culturist is familar with the almost infinite capacity of variation, which vegetable forms of life possess. Equally familiar is the method of obtaining strains or varieties by a process of selection. And if this selection has for its object the production of varieties fitted for particular physical conditions, the horticulturist is only doing what nature does unceasingly, though more slowly. The apparent inherited rigidity of form and structure which might seem a law to those who are unfamilar with living forms is non- existent for the gardener. Plants are all but plastic in his hands, and to any one who has ever compared the original stock of some one of our even comparatively modern garden plants with

the varieties now in cultivation, will see little presumption in saying that had we eternity to work in—within the limits, it is true, which nature prescribes—we might clothe the earth's surface with what pattern of vegetable raiment we liked.

Not that in this there is, after all, much, room for arrogance. Man can, after all, only guide the course of the variation which is the heritage of all living things, and which he has not initiated and cannot arrest. Man's sesthetic gratifications are only one more controlling physical condition imposed on quaquaversal variation. A change in one direction leads to the 'destruction of the individuals which exhibit it, because it traverses some physical condition ; a change in another, because it offends the gardener's standard of pleasurable colour or form.

Assuming, as is most probable, that the oldest types of flowering plants (excluding Gymnosperms, which are really very differently constituted) were self-fertilised, we have in the two empirical facts that all living things vary slightly from generation to generation, and that cross-fertilisation increases both vigour and fertility, causes sufficient to account for all the structural diversities of flowers. For example, we know from the experience of gardeners that flowers can be modified both in size and colour,— the one can be increased and the other intensified. If, therefore, Nature seeks to attract insects to inconspicuous, self-fertilised flowers, the simplest way of effecting it is by making the flower larger and gayer in colour. Now, taking, as Sir John Lubbock does, a genus like Geranium, we see that a- mongst its species we have precisely such a correlation as we might a priori have expected. The larger, brilliant flowers are those which have lost the power to fertilise themselves, the smaller, in conspicuous ones still preserve it. Some plants, like the common sweet violet, bear both conspicuous and incon- spicuous flowers. The former are adapted for cross, the latter for elf-fertilisation. When, however, we turn to the wild pansy, we find all the flowers adapted for cross-fertilisation. Thus, Mr. Darwin tells us, "When I covered up a fine, large cultivated variety, it set only eighteen capsules, and most of them contained very few good seeds, several only from one to three ; whereas an -equally fine uncovered plant, growing close by, produced 105 fine -capsules." These facts point to the conclusion that in such a case as the sweet violet, we have in the late inconspicuous flowers a survival of the old type possessed by the ancestor of all the violets ; in the pansy these have altogether been lost.

One remarkable point which is brought out by facts of these kinds is the unity of sensory gratification throughout the animal world. The colours and odours that please us please insects, the sweets that delectate us suit their taste, the fruits that we culti- vate are but too acceptable to birds. In the case of colour, its appreciation by insects has been rather taken for granted. But Sir John Lubbock tested it by experiment :—

"I placed slips of glass with honey on paper of various colours, accustoming different bees to visit special colours, and when they had made a few visits to honey on paper of a particular colour. I found that if the papers were transposed, the bee followed the colour." (p. 12.)

Space will not permit us to give any examples of the detailed adjustments which are described in Sir John Lubbock's pages, and, indeed, without being to some degree technical or having recourse to diagrams, it would be difficult adequately to explain them by words alone. Nor can we more than advert to the way in which, if insects have controlled the evolution of the floral form, flowers, in their turn, have acted on insects.

There is one consideration which may be suggested, and our readers may then be left—at least those who are interested in such matters, and they ought not to be few—to test the facts for themselves, as it is easy enough to do.

Suppose we could trace up all flowering plants to their remote ancestor—the Adam of the floral world—it would be, in our eyes, an unlovely plant, with inconspicuous flowers. Suppose, moreover, it were subject to the same laws of reproduction and variation as we know its descendants exhibit. Then this plant would implicitly determine the future existence, by virtue of that sub- jection of all the forms which are about us now. In point of fact, to create that plant under such conditions was to create all the wonderful variety that has issued from it. To use a mathe- matical analogy, we might compare the plant to a function, its stream of descendants to the series into which the function might be expanded. Or if that is too technical, we might re- present to ourselves the orderly sequence of descendants, becom- ing more and more attractive in shape and colour, to the gradual expansion of a flower-bud, which in its earliest state of immaturity gives little or no promise of its completely developed state, although that developed state is implicitly determined by it.