by Grant Allen
When we cut open the hood of the Æthiopian lily, we find inside it a spike somewhat resembling that of the cuckoo-pint, but differing in one or two important particulars. Near the bottom, at a point corresponding to that where the female flowers grow in the wild English arum, the white Æthiopian lily has a number of small greenish knobs, apparently embedded in a golden yellow matrix; at the top, the whole of the spike consists of a similar golden-yellow substance, which, at a certain period in the flowering process, effloresces, so to speak, with a copious greasy white dust, something like starch or wheaten flour. But if we split down the spike itself through the centre, we can soon find out what is the meaning of this curious arrangement. The golden substance which makes up the mass of the spike consists really of innumerable yellow stamens, packed so tightly together over the whole stem, and so closely sessile (as we call it technically) upon the central axis, that they look like a single piece of homogeneous waxy material. You can separate them from one another, however, with your fingers, and then you see that each one is roughly pentagonal or hexagonal in outline, owing to the pressure of its surrounding neighbours, and that it consists essentially of a small pollen bag, containing a quantity of yellowish liquid. When the stamens are quite ripe, this liquid assumes the form of small white pollen grains, which are pushed out as the bags open, and become the efflorescence or powder that covers the spike in its ripe state. At the bottom of the spike, where we get the pistil-bearing flowers in the cuckoo-pint, the Æthiopian lily has several small blossoms intermediate between the perfect flowers of the acorus, or the half-perfect flowers of the marsh calla, and the very imperfect flowers of the arum; for each of them has here a central green knob or capsule, surrounded irregularly by four or five stamens, but without any petals, or even any scales to represent them. These form the green bodies which I have already described as apparently embedded in a hard yellow matrix; and that yellow matrix is composed of the stamens. The lower part of the Æthiopian lily, in fact, consists of irregular flowers which, like those of the marsh calla, have quite lost their petals, but which still retain an indefinite number of stamens grouped around a single pistil; while in the upper part, as in the central group of the arum, the pistils have disappeared also, and only the stamens remain. Such a plant as this lily, then, is clearly on the way to becoming what the arum has actually become: its flowers already show a tendency toward the unisexual condition. In the upper portion they have all become actually unisexual, for there we get nothing but stamens; in the lower part they remain irregularly bisexual, for there, though the stamens are often reduced in number — nature losing count again — some of them still remain embedded on the spike between the scattered pistils. This result is just what you might naturally expect from squeezing a lot of marsh calla blossoms closely together on a spike. Even in the upper half of the spike, the blossoms often keep up some marks of their original bisexual character, for you will occasionally find a few stray green knobs sparsely sprinkled here and there among the golden stamens of the top portion. Nevertheless, we may fairly say that even here a tendency towards specialisation has been distinctly set up: the uppermost flowers tend to become almost entirely pollen bearing sacs, and the lowermost flowers tend to become preponderatingly, though not entirely, seed-bearing ovaries.
Now if we turn from these transitional steps to the completely developed arum, what do we find? Here, the top of the spike has become absolutely bald and bare of flowers, instead of being covered, as in the Æthiopian lily, with thickly grouped florets up to its very summit; and at the same time, the actual flowers in the lower portion, instead of running together into an uninterrupted cone, are separated into three distinct groups or bodies. At the bottom of all, as in the Æthiopian lily, we now get the female flowers alone; only, instead of being intermixed with stamens, they consist simply of naked ovaries; the differentiation or specialisation of the flowers is here complete. Above them, as before, we get the male flowers, reduced to a single stamen, or rather to a group of from four to six stamens each, all run together: for though it is usual to consider each stamen as a separate flower (which it certainly is in some still more degraded arums, like the little ‘Capuchin’ of southern Europe), I think the analogy of marsh calla and the Æthiopian lily justifies us in regarding them as groups of six, more or less defective, and jammed closely together, with the ovaries crushed out between them. And at the top of all we get a perfectly new factor in the compound community — a number of green sacs capped by downward-pointing hairs, which are, in fact, abortive pistils, like those organs that form the lower group, only with their ovaries barren, and their styles or sensitive surfaces lengthened out into spiky hairs. What may be the use or function of these curious objects we will proceed to inquire a little later: for the present we must turn our attention to the origin of another part of the cuckoo-pint’s apparent blossom, the large and conspicuous greenish-purple hood, which alone composes the flower in the popular sense of the word.
There is nothing at all like that, a casual observer would probably be tempted at first to say, in any ordinary true lily that any one ever yet came across. A bunch of lilies growing on a stalk, with a sort of huge winding-sheet wrapped round them, is a thing that surely nobody has ever seen. So it would seem at a first glance; and yet there is one lily-like plant that we all know well, in which the flowers are at one time wrapped up in exactly such an enveloping sheet. Have you ever watched a narcissus or a daffodil unfolding its pretty yellow buds? If you have, you will remember that at first they are all tightly covered over by a thin papery membrane, shaped exactly like the hood of this cuckoo-pint; and that after the scented blossoms have all come out, this membrane, or spathe, as we call it in the horrid technical language of botany, turns back upon the stem, like a sort of cup below the flowers. To be sure, the daffodil and the narcissus are not, in the strictest sense of the word, true lilies at all, but amaryllids, because they have got an inferior instead of a superior ovary; but, even in the technically restricted lily family itself, there are lilies with just such a spathe or enveloping membrane, as in the familiar head of onions and garlic, as well as in some more respectable and dignified flowers. Now, one has only got to suppose the number of buds in each head largely increased, the whole head lengthened out into a spike, and the spathe or sheath grown larger into a completely inclosing hood, and there we have at once an arum or an Æthiopian lily. Only, as often happens under such circumstances, the individual flowers have now grown too small to attract the fertilising insects separately on their own account; so the spathe or hood has to do duty for them all at once collectively. It incloses and conceals the various minute flowers, but it becomes itself coloured and attractive, so as to allure the eyes of the little insects on behalf of the entire community. In other words, when the central flowers had become so much diminished in size by disuse, by loss of their petals, and by specialisation of sexes, they ran no chance of getting fertilised at all unless they possessed some exceptional means of attracting insects. Hence those alone have survived which happened to develop some such attractive organ as the hood of the Æthiopian lily or the purple central spike of the English arum.
And now we come at last to the final purpose of all these curious structural arrangements. The object of them all is of course to ensure the cross-fertilisation of the different heads of flowers; but the special way in which they effect this universal end is singularly ingenious, interesting, and almost intentional in its design. The Æthiopian lily, one can readily understand, attracts many insects by its large brilliant white hood, as well as by the rich golden-yellow colour of the stamens which cover the summit of its spike. But in the arum the top of the spike is bare, and has become expanded into a club-shaped organ, which is deeply tinged with purple, and stands out vividly against the bright green of the spathe at its back, so as to form an excellent advertisement for the giddy eyes of little passing winged insects. It is upon these insects that the arum depends entirely for fertilisation, and the way in which it
manages to obtain their services is as curious as anything in the whole range of vegetable existence.
If, when the arum-flowers are just beginning to blossom, I were to cut down one of the hoods halfway through the centre, sideways, I should find a great many tiny winged flies all crawling about at the very bottom of the deep tube. They have come from some other neighbouring arum-flower, where they have been well dusted with the golden pollen; and they crawl down the neck of the hood, past the lobster pot hairs which close its narrowest portion, into the broader open space beneath. Here they find the pistil-bearing blossoms just ripe for impregnation; and, crawling over them in an aimless sort of fashion, they rub off upon their sensitive surfaces some of the pollen which they brought with them from the last plant they visited. This pollen thus cross-fertilises the fruit, and produces in it seeds which are the product of two distinct parents, and therefore capable of springing up into vigorous seedlings of the strongest sort.
But though the small flies have thus benefited the plant by fertilising its ovaries with pollen brought from another head, they have as yet got no return for their trouble in the shape of meat or drink: and, unless they did so, they certainly would not take the trouble to visit any other flower of the same sort. The stamens are not yet ripe, and do not ripen until after the pistils have set their fruit. If they did otherwise, then the pollen would fall from them down upon the sensitive surfaces of their sister blossoms below, and the plant would accordingly be self-fertilised — a thing to be always avoided as far as possible. Accordingly, it is a fixed rule in the cuckoo-pints that the pistils, which are below, come to maturity first, while the stamens, which are above, shed their stock of pollen a day or two later. This being so, the flies find nothing in the new flower to detain them any longer; and, if they could, they would crawl up the spike and get out again by the same way as they got in, never troubling themselves any more about such useless flowers. Here, however, the curious lobster-pot hairs for the first time come into play. They act, in short, exactly like a common eel-trap. The flies walked in easily enough, the way the hairs naturally pointed; but when they try to walk out again, they find their way completely blocked by the chevaux-de-frise of stiff bristles. There is nothing that beats a crawling insect like a thicket of hairs; he finds it as impossible to creep up against their grain as we ourselves find it to force our way through a tropical jungle of cactus and prickly spurges. So there they wait perforce for a time in durance vile, wandering up and down helplessly among the lower flowers, and effectually brushing off against them every single grain of pollen which they brought on their legs or breasts from the last flower they visited.
At last, in a day or so, the young berries begin to swell slowly, and all the pistil-bearing flowers show by this quickening action that they have been duly and properly fertilised. Then comes the turn of the stamens. One after another they open their little double pollen-sacs, and shed their golden powder down upon the wings and bodies of the small flies imprisoned beneath. Even if a little of it happens to catch upon the pistils here and there, that does not matter now, for all the ovaries are already duly impregnated, and the sensitive surfaces have shrivelled utterly away; so most of the pollen falls on to the floor of the hood, where the small flies are waiting impatiently and hungrily for the Danae flood. It covers them all over from head to foot with the golden grains, and clogs their legs and wings and bodies in every portion. A fine time the flies have of it then. They get actually drunk with pollen after their fast; and, if you cut open one of the hoods in this stage of development, you will find the little creatures positively reeling about in their intoxication, and so full-fed with rich grains that they can hardly use their legs or wings to crawl or fly. A little fresh air seems to revive them slightly, as is often the case with other gentlemen under similar circumstances; and then they can feebly fly away after a few minutes.
But in the natural state of things, when no wandering botanist comes with his penknife to make what he calls in his lively language a ‘longitudinal section of Arum maculatum,’ the flies remain at the bottom of their deep well till they have eaten almost all the pollen, and got most helplessly and stupidly drunk in the process. A great waste of pollen this, for the plant, of course; but still it costs no more than honey would do, and quite enough remains on the legs and wings of the flies to impregnate their fellow-blossoms on another plant. At last all the pollen is shed and eaten, and then the flies again become anxious to shift their quarters to some more favourable spot, where there is more food to be found, and another drunken orgy to be expected. This time, however, the hairs no longer impede their progress; they have all shrivelled up meanwhile, and the eel-trap is therefore now dissolved; so the flies hurry away once more, covered with the stock of pollen-dust which has been showered down upon them by their late host.
One might suppose, at first, that after one such experience the flies would studiously avoid cuckoo-pints in future. Nothing of the sort. Experience seems to be thrown away upon insects; and besides, the little creatures seem actually to enjoy their intoxicated revels. Pollen apparently acts upon them as an incentive, exactly as opium acts upon a Chinaman. The first thing they do the moment they are released is to forthwith fly off to the nearest other cuckoo-pint. They see a purple, club-shaped spike, somewhere close by, overtopping the folded lips of the green hood, and they make straight for that well-known signpost, as the lordly human race makes for the flaring lights of a gilded public-house. Once more they crawl down the funnel-shaped tube; once more they pass the eel-pot hairs; and once more they rub off the pollen that clings to their legs and sides upon the sensitive surfaces of the lower flowers. For a while they have again to fast in their narrow prison; and then the stamens of the second arum open their pollen-sacs, and dust the greedy insects a second or third time with golden grains. So, throughout the whole flowering season of the arums, these little flies go about from head to head in constant relays, unconsciously benefiting the plant, while they are effecting their own hungry purpose in eating up the spare pollen. From the point of view of the insects, the only use of arums is to produce food and shelter for wandering flies; but from the point of view of the plant, the only use of insects is to act as common carriers for the conveyance of pollen from one head to another. Man, however, is far wiser and more expansive in his ideas about the economy of nature than either: according to him, the real, final end of all this beautiful and marvellous mechanism is to produce Portland arrowroot for starching his own civilised shirt-fronts, wristbands, and collars.
After the dissolute small flies have performed their function in the economy of the cuckoo-pint by thus fertilising the small green ovaries, the plant begins to enter upon a fresh phase of existence. It has now no further use for its hood and its purple-topped spike, which have answered their purpose in attracting the insects; and therefore it gets rid of them in the same summary way in which mankind generally get rid of a faithful old horse, or a superannuated servant. The hood withers slowly away; the top of the spike, as far down as the base of the cluster of stamens, gradually decays; and at last you find nothing left but a bunch of rather shapeless green berries, elevated on a stiff, fleshy stalk, and with a scar at their bottom in the place where the hood used once to join on. As summer wears away the berries grow bigger and bigger, while at the same time they become redder and redder. At last, with the first approach of autumn, they appear as the bright cluster of coral-coloured berries, represented at the side, with which we are all so familiar in our September hedgerows.
Fig. 54.
What is the use of this new manœuvre? Well, it is not simply that common to most succulent fruits. Each of these bright red berries incloses a single hard nut-like seed. Its object is to attract the fruit-eating birds, the field-mice, and the other small animals, to eat it up whole. For this end, just as so many flowers have bright-coloured petals to attract the eyes of insects, we know that fruits have bright-coloured pulpy coverings to attract the eyes of birds or mammals. And as the flo
wers put honey in their nectaries as an allurement for the bees, so the fruits put sugary juices in their pulp as an allurement for the robins and bullfinches. So far, the trick is just the ordinary plan of all fruit-bearers. The arum, however, has a still more cruel and insidious mode of procedure. Its berries are poisonous; and very often, I believe, they destroy the little birds that they have enticed by their delusive prettiness. Then the body of the murdered robin decays away, and forms a mouldering manure-heap, from which the young cuckoo-pint derives a store of fresh nutriment. I will not positively assert that it is for this reason the cuckoo-pint has acquired its poisonous juices; but I cannot help seeing that if any berry happened to show any tendency in such a direction, and so occasionally poisoned the creatures which eat it, it would thereby obtain an advantage in the struggle for existence, and would tend to increase the poisonous habit so far as it continued to obtain any further advantage by so doing. To some people this may seem grotesque; but the grotesqueness is in the facts of nature, not in the appreciation of their inevitable results. Poisonous berries are unquestionably useful to the plants which bear them; and, if we find their usefulness ridiculous, that is a peculiarity of our own sense of humour which in no way affects the abstract truth of the observation. It is impossible, in fact, that a plant should not benefit by having its berries poisonous, and so some plants must necessarily, in the infinite variability of nature, acquire the property of killing their friendly allies. It has been asked why the birds have not on their side learnt that the arum is poisonous. The very question shows at once an ingrained inability to understand the working of natural selection. Every bird that eats arum berries gets poisoned: but the other birds don’t hold a coroner’s inquest upon its body or inquire into the cause of death. Naturally the same bird never eats the berries twice, and so experience has nothing more to do with the matter than in the famous illogicality about the skinning of eels.
