The same is true of the Impatiens fulva. This is an American plant, closely akin to the balsam of our gardens, which has now thoroughly established itself on the banks of some of our rivers, as the Wey, and the tributary stream that runs through Abinger and Shere. It has attractive flowers hung on the daintiest flower-stalks. It has also little green flowers that never open and almost escape attention; and yet they, and not the large flowers, are the great source of seed vessels to the plant—the great security that the life of the race will be continued.[18] Again, ugliness has borne away the palm of utility from beauty.
So, too, in America the same happens with the Specularia perfoliata: in shady situations all its flowers are said to be cleistogamous, and to be wonderfully productive and strong.[19]
The conditions of the problem in these cases are such as to make them of the last importance in our inquiry into the utility of beauty; for in each case we are comparing a conspicuous and an inconspicuous flower in the very same plant. The conditions seem to exclude the possibility of error in the result.
Two explanations have been suggested of the origin of these cleistogamous flowers: according to the one, they are the earliest form of the flowers; according to the other view, they are degraded forms of the more beautiful flowers.[20] For our purpose, it is immaterial whether of the two explanations is correct; for either the development of beauty has diminished the utility of the flower, or the loss of beauty has increased the utility: in either event, utility and beauty are dissociated the one from the other.
Another experiment Nature presents us with, in which the conditions are nearly, if not quite, as rigorously exclusive of error. The vast majority of orchidaceous plants are, as already mentioned, dependent on insect agency, for fertilization, and present a marvellous variety of contrivances for effecting cross-fertilization through their activity. But one of our orchids (the Bee orchis) is self-fertilized. I hardly know anything in vegetable life more striking or beautiful than to see its delicate pollinaria at a certain stage of its inflorescence descending on to the stigmatic surface and so yielding their pollen grains to the fertilization of their own blossom; and yet the Bee orchis has been found by observers to be as free a seeder as any of its tribe. Here the beauty and conspicuousness of the blossom, which are very great, are, as far as can be seen, useless; the plant gains nothing by the attractiveness which it offers, and the colouring and ornamentation of the blossom are, on the theory of utility, residual phenomena.
It is difficult to imagine that the change from wind or self-fertilization can, so to speak, commend itself to the flower on the score either of economy or success. If the anemophilous blossom must produce somewhat more pollen than the entomophilous, it saves the great expenditure of material and vital force requisite for the production of the large and conspicuous corolla. The one is fertilized by every wind that blows; the other, especially in the case of highly-specialized flowers like the orchids, may be incapable of fertilization except by a very few insects. The celebrated Madagascar orchid Angræcum can be fertilized, it is said, only by a moth with a proboscis from ten to fourteen inches long—a moth so rare or local that it is as yet known to naturalists only by prophecy. It is difficult to suppose that it would be beneficial for the plant's chance of survival to exchange as the fertilizing agent the universal wind for this most localized insect.
And here another line of evidence comes in and demands consideration. The face of Nature, as we now see it, has not been always exhibited by the world. The flora, like the fauna, of the world has changed: how has it changed as regards the beauty of the flowers? Does it give any testimony to that becoming beautiful of the flowers of plants to which Mr. Darwin refers? The answer is not a very certain one, by reason of the imperfection of the geological record, of the probability that beautiful plants, if they had existed, and had been of a delicate structure, would have perished and left no trace behind. But so far as an answer can be given, it is in favour of the increase of floral beauty in the vegetable world. The earliest flower known (the Pothocites Grantonii) occurs in the coal measures; its flowers cannot have been other than inconspicuous in themselves, though it is possible that by grouping they were made more attractive to the eye; in the period of the growth of the coal, when this plant lived, the vast forests seem principally to have been composed of trees without conspicuous blossoms, huge club mosses and marestails, and many conifers; in the earlier periods of this earth we have no trace of conspicuous blossom, and it is not till the upper chalk that the oaks and myrtles and Proteaceæ appear as denizens of the forests. In like manner, if we refer to the appearance of insects on the earth, we have no clear trace in very early strata of those classes of insects which now do the principal work of fertilization for our conspicuous flowers. In the coal measures there have been found insects of the scorpion, beetle, cockroach, grasshopper, ant, and neuropterous families; but of a butterfly or moth there is only evidence of great doubt. It seems probable, then, and one cannot say more, that with the progress of the ages, flowers, as a whole, have become more conspicuous and attractive. But if we inquire whether the dull flowers of one era have grown into the conspicuous flowers of another, the answer is negative. The conifers of the coal age were anemophilous then, and are anemophilous still; they show no symptom of becoming more conspicuous; the same is true of the oaks of the chalk period, and of all other inconspicuous plants. The difference between conspicuous and inconspicuous flowers appears a permanent one; and the page of geology gives no evidence in favour of the supposed change.
Another observation must yet be made. Comparing flowers fertilized by insects and by the wind, it has never, so far as I can learn, been observed that the former are more certain of being set or more prolific than the latter; and, as already shown, the inconspicuous flowers are often more fertile than the conspicuous ones. What motive would there be, then, for the inconspicuous flowers of the early geologic periods to convert themselves into the brilliant corollas of our day?
Carefully considered, the passage which I have cited from Mr. Darwin does not account for the beauty of the flowers of plants at all; it accounts only for their conspicuousness, as the writer himself points out; and the two things are so different, that to account for the one is not even to tend to account for the other. If any one will consider the beauty of every inflorescence, whether conspicuous or not—a beauty which the microscope always makes apparent where the unaided eye fails to perceive it; or, again, the easily perceived beauty of many inconspicuous plants; or, lastly, the beauty of many conspicuous plants which does not tend to their conspicuousness—he will see how true this is.