Works of Grant Allen

by Grant Allen

  Perhaps it may be asked, How do I know that the salad-burnet is not descended from the stanch-wound, rather than the stanch-wound from the salad-burnet? At first sight this might seem the simpler explanation of the facts, but I merely mention it to show briefly what are the sort of grounds on which such questions must be decided. The stanch-wound is certainly a later development than the salad-burnet; and for this reason — it has only four stamens, while the parent plant has several, like all the other roses. Now, it would be almost impossible for the flower first to lose the numerous stamens of the ordinary rose type, and then to regain them anew as occasion demanded. It is easy enough to lose any part or organ, but it is a very different thing to develop it over again. Thus the great-burnet, having once lost its petals, has never recovered them, but has been obliged to colour its calyx instead. It is much more natural, therefore, to suppose that the stanch-wound, with its few stamens and its clumsy device of a coloured calyx instead of petals, is descended from the salad-burnet, than that the pedigree should run the other way; and there are many minor considerations which tend in the same direction. Most correctly of all, we ought perhaps to say that the one form is probably a descendant of ancestors more or less like the other, but that it has lost its ancestors’ acquired habits of wind-fertilisation, and reverted to the older methods of the whole tribe. Still, it has not been able to replace the lost petals.

  I ought likewise to add that there are yet other roses even more degenerate than the burnets, such as the little creeping parsley-piert, a mere low moss-like plant, clinging in the crannies of limestone rocks or growing on the top of earthy walls, with tiny green petalless flowers, so small that they can hardly be distinguished with the naked eye. These, however, I cannot now find space to describe at length; and, indeed, they are of little interest to anybody save the professional botanist. But I must just take room to mention that if I had employed exotic examples as well as the familiar English ones, I might have traced the lines of descent in some cases far more fully. It is perhaps better, however, to confine our attention to fairly well-known plants, whose peculiarities we can all carry easily in our mind’s eye, rather than to overload the question with technical details about unknown or unfamiliar species, whose names convey no notion at all to an English reader. When we consider, too, that the roses form only one family out of the ninety families of flowering plants to be found in England alone, it will be clear that such a genealogy as that which I have here endeavoured roughly to sketch out is but one among many interesting plant pedigrees which might be easily constructed on evolutionary principles. Indeed, the roses are a comparatively small group by the side of many others, such as the pea-flowers, the carrot tribe, and the dead-nettles. Thus, we have in England only forty-five species of roses, as against over two hundred species of the daisy family. Nevertheless, I have chosen the rose tribe as the best example of a genealogical study of plants, because most probably a larger number of roses are known to unbotanical readers than is the case with any other similar division of the vegetable world.

  VIII. CUCKOO-PINT.

  Fig. 50. — Cuckoo-Pint (Arum Maculatum).

  Close by the hedge-side there runs a little streamlet known to the village children for two miles around by the strangely pleonastic title of the Bourne Brook. Pleonastic, I say, because bourne is, of course, good old English for what in modern English we call a brook, so that the two halves of the common name are, in fact, synonymous, the later word being added to the earlier by the same sort of unconscious reduplication as that which gives us the double forms of Windermere Lake or Mount Ben Jerlaw. I can’t tell you, though, what a world of life and interest is to be found among the low cliff banks and tiny shingle patches that bound the Bourne Brook. In the stream itself there are darting crayfish, which we can catch with our fingers by lifting up the green slimy stones; there are caddis-worms, and big pond snails, and pouting miller’s thumbs, and iridescent stickleback; it is even rumoured, though I doubt whether on sufficient authority, that there are actually and positively in some of its pools and stickles genuine unadulterated real live trout. I know as a fact, however, that there are freshwater mussels, for these I have fished up with my little dredging-net, and safely domesticated in the bell-glass aquarium. In the fields around there are ferns, and marsh-marigolds, and rushes, and roast-beef plants. And beside the water’s edge there are abundant leaves and blossoms of that strange flower the cuckoo-pint, whose counterfeit presentment you see in the figure on the previous page. Now, cuckoo-pint, or lords-and-ladies, or wild arum, whichever you choose to call it, is a very singular plant indeed; and it seems to me we cannot do better than sit down and dissect one for the sake of understanding its queer internal arrangements. If it were a newly discovered Central African lily, we should all be reading about its extraordinary adaptations in all the newspapers: much more then, since it is a common English plant we have all known familiarly from childhood upward, ought we to wish for some explanation of its singular shape and its wonderful devices for entrapping and intoxicating helpless little flying insects.

  First of all, we must begin by recognising that the apparent flower of the cuckoo-pint is not one single blossom, but a whole group of separate blossoms, closely crowded together in two or three little distinct bundles on a long spike or succulent stem. And in order to let us all clearly understand the meaning and nature of the entire compound structure, I think we had better divide our subject (as if it were a sermon) into three heads. First, we must consider what are the actual parts to be distinguished from one another in the flower of the cuckoo-pint at the present day. Secondly, we must ask what was the course of evolution by which they each assumed those peculiar forms. And thirdly, we must inquire what good purpose in the economy of the plant is subserved by each part in the existing cuckoo-pints as we now find them. We shall thus have learnt, at last, what a cuckoo-pint is, how it came to be so, and why its various portions have been brought to assume their present forms.

  Fig. 51.

  Spadix of Arum.

  Beginning, then, with the purely structural or positive arrangement of the cuckoo-pint as we find it in nature at the present day, we see at once that its blossom consists mainly of a large greenish-purple sheath or hood, at the top of a long stalk, inclosing a tall fleshy spike or club, shaped something like a mace, and protruding from the hood in front, so as to show its coloured and expanded summit above the point of junction of the two lips. That is all that one can see of the blossom from the outside; but in reality these two conspicuous organs form no part of the actual and genuine flowers themselves at all. They are merely incidental accessories, put there for an excellent purpose indeed, as everything always is in the balanced economy of nature; but not essential or necessary to the existence of the flowers as flowers, though most noticeable from their size and hue to the superficial eyes of the unscientific human kind. In order to see the true flowers themselves, we must cut open the side of the hood or sheath, as has been done in the accompanying diagram, and then one can observe a number of small knobby bodies clustering in three groups along the lower part of the club-shaped spike or central axis. Those little knobby bodies, of which there are a great many in each arum, form the real blossoms of the cuckoo-pint; and they are inclosed in the sheathing hood for a very good reason, as we shall hereafter see, in order to ensure the carrying out of their proper function, the final production of seeds and berries.

  If one looks closely at the diagram, however, one can notice that these little knobby flowers are not all quite similar to one another. They consist of three distinct kinds, all three of which are always found in true arums of this type. At the bottom there are a whole group of small cushion-like green lumps, each with a little point in its centre, and all closely packed together in several irregular rows, like Indian corn on the cob. These green lumps are the pistil-bearing flowers; each of them represents a single very degraded blossom, and each will grow out at a later stage into one of the bright scarlet berries which form su
ch beautiful objects in the hedgerow and waysides during the autumn months. We could not possibly have a simpler type of flower than these lowest pistil-bearing blossoms; they are in fact the central floral notion reduced to its ideally simplest terms. They consist each of a single rudimentary berry, containing a single seed, and crowned by a little point or stigma, which is the sensitive surface to be fertilised by the pollen from the other flowers.

  In the middle, here, come the flowers of this second or pollen-bearing sort, each of which again consists of naked stamens; that is to say, each flower is here reduced to one solitary part, analogous to the little pollen-sacs that you see hanging out in the centre of a tiger lily or most other conspicuous garden blossoms. Every such stamen is made up of two tiny bags, which open when ripe and discharge their golden pollen. Though the pollen looks to the naked eye like mere yellow dust, yet, when put under a microscope, it is seen to consist of small egg-like bodies, having a characteristic shape and appearance in each different flower, exactly as the seeds and fruits have to the naked eye. With these two essential elements of floral architecture we are now pretty familiar from our previous examination of other plants.

  On top of all, however, come a group of very peculiar blossoms, found only in the arum and nowhere else, and consisting of several little green knobs, like those of the pistil-bearing flowers, but each crowned by a long hair or filament, bent downwards towards the base of the hood or sheath, and very much larger than the sensitive surface of the lower blossoms. The origin and meaning of these peculiar organs we will come to consider later on: for the present it will be sufficient to observe their shape and position, and to notice that their hairs point downward and inward like the spikes of a lobster pot, at a point exactly corresponding to the narrowest neck or throat of the inclosing sheath.

  And now, how did the cuckoo-pint come to possess this very singular arrangement of tiny separate flowers in a close spike, female below, male in the centre, and neuter or rudimentary on the top of all? To answer this question properly, we must go back to the earlier ancestors of the arum tribe — and I may as well start fair by saying at once that the arums are by descent degenerate lilies, like wheat, and that each of these very degraded little flowers really represents a primitive full-blown and bright-coloured lily blossom. You will remember that a true lily is made up of six brilliant petals or flower-leaves, inclosing six long pendulous stamens, and with a seed-vessel or ovary of three cells in the very centre. Such a blossom as that we call a perfect flower, because it possesses within itself all the component elements of any blossom — calyx, petals, stamens, and pistil. Moreover, it is, so to speak, a self-contained and self-sufficing flower; it has bright petals to entice an insect fertiliser, pollen to impregnate its ovary, and embryo seeds to form the future ripe fruit. But as we have so often noticed, it is highly undesirable for a flower to be fertilised with pollen from its own stamens: those plants which are impregnated from the stamens of their neighbours always produce more seed and stronger seedlings than those which are impregnated with home-made pollen from their own sacs. Hence, cross-fertilisation, we know, is the great end aimed at by all flowers; and those plants which happen to vary in any direction favourable to cross fertilisation invariably succeed best in the struggle for life, while those which happen to vary in any direction hostile to it, or which acquire the bad habit of self-fertilisation, tend slowly to go to the wall and to die out from inherited and ever-increasing feebleness of constitution.

  There can be very little doubt that the ancestors of the arums had originally six coloured petals like the lilies, for a reason which I will shortly mention; and inside these petals were six stamens and a three-celled ovary or unripe capsule. It is a very long step, certainly, from such perfect flowers as those to such very rudimentary and reduced types as the little florets which we get in the cuckoo-pint, each consisting of a few stamens or a single one-seeded fruitlet, without any trace of petals whatsoever. Yet we have very good evidence of the slow course of degradation by which the arums have reached their present condition; and, as happened in the case of wheat, several surviving intermediate forms enable us to bridge over the intervening gulf. In other words, there are plants which resemble the lilies in some things, while they resemble the arums in others; and by means of these plants we can trace a regular gradation from the perfect and bright-coloured flowers of the true lily to the imperfect and inconspicuous little unisexual blossoms of our English cuckoo-pint. It is interesting, too, to observe how the very same original stock which in one direction gave birth to the degenerate wind-fertilised wheat and grasses, has in another direction given birth to the equally degenerate but insect-fertilised arums and their congeners. The one case shows the course of degradation as it takes place in poor dry soils; the other case shows it as it takes place in the moist and rich mould of watery ditches.

  Fig. 52. — Single flower of Sweet-sedge.

  Look first at the curious flower which is represented for us here in the little sketch at the side. In the slow rivers of Suffolk, and along the shallow edges of the Norfolk broads, there grows a pretty spiky water-plant, known by the scientific name of Acorus, or by the simpler English titles of sweet-flag and sweet-sedge. This acorus is a highly aromatic reed-like plant, with long lance-shaped leaves, and a dense spike of small yellowish-green blossoms, standing out in a cylindrical form from the thick rod which does duty for its stem. At first sight you would not say that these flowers differed very much from those of the arum: they look pretty much the same sort of small unnoticeable green knobs to a casual observer. But when one comes to pick out one of them from the close mass, and to examine it with a common pocket lens, one can see at once that, though very much reduced in size and colour, it is still at bottom essentially a lily flower. In the diagram we have one of these small blossoms considerably enlarged, and it is easy to see that it possesses all the various parts which characterise the true lilies. There are six petals, clearly enough, though they are minute and green instead of being brilliantly coloured; and they are closely folded over the central organs, instead of being bent back and displayed ostentatiously to the eyes of passing insects. There are six stamens too, one under each petal, almost concealed by the scale-like covering; and in the centre there is an ovary which when cut across proves to have sometimes two and sometimes three seed-bearing cells, for the number here has become a little indefinite: nature, as so often happens, has begun to lose count. There can be no sort of doubt, then, that acorus represents a very reduced and degraded lily, still retaining all its primitive structural arrangements, but with its flowers greatly diminished in size, and with its original bright colour almost entirely lost by disuse and degradation.

  The reason why this little acorus or sweet-sedge has thus gone backward in the course of development is not a very difficult one to understand. Brilliant flowers like the lilies depend for fertilisation upon large colour-loving insects, such as bees and butterflies, which are attracted by their flaunting hues and their abundant store of rich honey, and so unconsciously carry the impregnating pollen from head to head. But many other plants find it suits their purpose better to depend either upon the wind or upon small insect friends of less pronounced æsthetic tastes; and this is especially the case, among other classes, with almost all waterside plants. Hence such plants have usually acquired small and inconspicuous separate flowers; and then, to make up for their loss in attractiveness, like cheap sweetmeats, they have very largely increased their numbers. Or, to put the matter more simply and physically, in waterside situations those plants succeed best which have a relatively large number of individually small and unnoticeable flowers, massed together into large and closely serried bundles. Hence, in such situations, there is a tendency for petals to be suppressed, and for blossoms to grow minute; because the large and bright flowers seldom succeed in attracting big land-insects like bees or butterflies, while the small and thick-set ones usually do succeed in attracting a great many little flitting waterside midges. Exa
mples may be found in the rushes, bur-reeds, catstails, and many other freshwater plants.

  For such a rôle our friend the sweet-sedge is peculiarly well adapted. Its small yellowish blossoms, though separately unnoteworthy, are rendered conspicuous in the mass by their dense grouping: and its extremely aromatic perfume makes it a great favourite with the tiny flies and water-haunting insects, who are much more guided in their search for food by scent than by sight. These little flies carry its pollen from one head to another, and so unconsciously fertilise the future seeds, and give the plant a firm foothold in all situations which are naturally suitable for its peculiar mode of growth.

  Fig. 53. — Single flower of

  Marsh Calla.

  The common marsh calla of northern Europe (fig. 53) bridges over the gap between this English plant and the stages below it on the path of degradation. Calla has by disuse quite lost its petals, but it nevertheless retains six stamens to each flower, grouped round a single ovary. Here the close relationship to the true lilies still remains quite apparent.

  Next in descending order, on the way to the cuckoo-pint, we may take that common white lily which grows so often in cottage windows, and which boasts more names, Latin and English, than almost any other plant whose personal acquaintance I have ever had the pleasure of making. The members of a Sheffield long firm themselves have seldom so many aliases as this honest and unoffending flower. Botanists call it Richardia Africana; gardeners dub it Calla Æthiopica; and the general public knows it indiscriminately as Æthiopian lily, white calla, snowy arum, St. Helena arrowroot, and lily of the Nile. However, in spite of its numerous disguises, I dare say it will be easy to recognise the plant I mean, when I say that it is very much like a cuckoo-pint, only with a pure snow-white hood, and a bright golden yellow spike projecting from the top. As in the cuckoo-pint this golden spike is the part which contains the true flowers; and the snow-white hood is only a sort of shroud or cloak which covers them in from the vulgar gaze. The Æthiopian lily, then (since we must choose one among its many names), presents us with a further step on the downward path of degradation from the true lilies towards the thoroughgoing cuckoo-pint: for, as preachers justly remark, there is no drawing a line after you have once begun upon the wrong track, and a lily which lets in the thin end of the wedge by becoming a sweet-sedge is almost certain to end at last, in the form of its remote descendants, as a mere degenerate and neglected arum.