by Tuffen West (1823−1891)
Reprinted from: West, T. 1860. Wonders of a stagnant pool. Recreative Science, vol 1: 154−157 (Source). We thank TintinnidGuy (@JohnDol84297193) for pointing out to this text by a 19th century British botanist.
After long confinement to the house, whether from illness or an unusual pressure of engagements, how delightful to turn out for a stroll in the fresh pure air ! Unheededwhether it rain or shine, if a naturalist of the true stamp, all around seems to welcome him, and care and trouble for the time fly far away. It was early in the morning, recently, that, in urgent need of a breath of fresh air, we started for a walk before breakfast; rain had fallen heavily during the night, and the air was still reeking with moisture. One trouble, and one alone, was ours during the walk − What shall we contribute to our readers in the next Recreative Science ? One subject we had given much time to presented so many new features requiring careful and prolonged examination, that it had to be left for further time and opportunities; so on in meditative mood we walked, till our thoughts turned to the teeming abundance of the lower classes of vegetable life, and the important part they play in the grand scheme of life on our globe.
Coming, then, to a stagnant, foetid ditch, our attention was caught by the unusual quantity of a blackish-green slimy-looking substance, at the bottom, sides, and floating on the top by means of entangled air. Some of this was gathered. A similar material by the side of the road, left by a now dried-up rain-pool, furnished another gathering, each, for lack of a better means of conveyance, being placed in a bit of paper, and transferred to the waistcoat-pocket. A little further on the palings, the trees, the very walls in parts, were covered with a bright green powdery-looking substance, as if they might have been recently painted, some of which was carefully scraped off"; and, lastly, nearly at our own door, we find on the gravelled path, at the base of tlie wall, a lively crisp-looking little vegetable, some of which, is secured, and we have material enough for some hours' careful examination, and, if time permitted, months, it may be years, of study.
Let us take out the microscope; some slides and thin glass-covers, and a tumbler of clean pure water, will be wanted; and it may be as well to have a little bottle of glycerine, and another of asphalte varnish, for the preservation of tbe subjects of examination. The magnifying power required will be tolerably high, say about two hundred diameters. We will take a little of the material obtained from the pool, black from the close crowding of the little threads composing it, remove it with the point of a penknife to a slide, and then put on a cover. In the meantime, the portion from which it was taken may be put into a watch-glass, or other shallow vessel, with a little water. Raise the tube of the microscope, lest the object-glass be injured by touching the slide or the water upon it, and carefully lowering it till rightly focussed, look what we have got. Why the whole field is in motion ! it looks as if we had a number of little slender worms, of a pale copperas, or verdigris-green colour, uniform in diameter, and with a sufficient power and good light, bars or stripes at short intervals may be seen passing across them. Here are some that look as if they might be fastened together like a bundle of faggots, with those on the outside writhing and twisting as if they would free themselves from an unwelcome embrace. Some have succeeded in the attempt, and are passing across the field with an undulatory motion; others are imitating the action of a pendulum, whilst here is one turning what might be taken for a head, with which it would see what is going forward behind it. The peculiar character of these movements has caused the name of Oscillatoriae to be given to the tribe (Fig. 1).
How do they move ? is the first question that suggests itself, and it is not easily to be answered; for upwards of a century has it been debated, and it is yet hung round with doubts. It has been suggested by Dr. Harvey, that the appearance of wave-like flexure and oscillation may be due to onward progress in a spiral direction. This view is entertained by Dr. F. D'Alquen, in a very able article in the Quarterly Journal of Microscopical Science (vol. iv. p. 245), where the whole subject is treated at length, and a source of motive power described in one species, which, if the author be correct, would be, so far as known, new and unique in the vegetable kingdom, an irritable contractile fibre passing down the centre of each filament. Our own observations lead us to think that the motion is really in a spiral direction, but to what it may be due we do not venture to give a decided opinion. One observation we made, however, seems very much to the point : on doubling our magnifying power in this instance, as represented at b (Fig. 1), a number of fine threads were seen projecting all round the end of the filament, to one of which a minute particle of dirt adhered; we could thus see that the filament was turning rapidly round, and found it difficult to resist the belief that the lashing of the water was produced by the active movements of cilia, and not merely by the passage through it of motionless processes. Such cilia, if indeed they be so, may occasionally be seen on other parts of a filament, and the most rapidly moving specimen we ever met with was furnished with them in unusual profusion. Before finally putting this down, let us add a drop of chloroform; the motion is instantly stopped, and laudanum produces a similar effect.
What relation is borne by Oscillatoria to other plants is yet a mystery. If we look at the dried-up material taken from the gravel path, it will be found to be motionless, in much shorter pieces, and those contained in gelatinous tubes; the same thing evidently, but in a different state. As it would have been impossible, before the changes had been observed, to predicate that from an egg, a motionless speck, should come an active, voracious caterpillar, which should turn again to a quiescent chrysalis, and whence should emerge at last a graceful volant denizen of air; so, till all the changes involved in the life-history of this simple vegetable are known, we are unable to say what phase the motive stage we have been examining may represent. Probably, when the pools or damp places it inhabits are slowly dried, it assumes the altered form with investing hyaline tubes; when quickly dried, each filament breaks up into its component joints (c), which are probably analogous to the buds of higher plants. Sometimes we find a portion assuming a different appearance, enlarged and thickened (d), with spaces on each side of it bare of colouring matter − such may be a sporange, or reproductive body; and there are good grounds for thinking we know but the caterpillar state, the connection of which with its perfect condition remains yet to be traced. To any who have taste for such an investigation, a rich reward in continually renewed interest may safely be promised, and it may be their good fortune to add another leaf to our yet most scanty knowledge of the "Book of Nature."
The "greenstuff" from the paling is a plant of another kind; like little beads of a rounded or oval form, and delicate grassy green colour (Fig. 2). Generally each little "bead" is free, sometimes two may be seen united, and occasionally four or six in short strings. If this be really a unicellular plant; if each of these little "beads," or "cells," as they are termed in scientific language, be really a plant in itself,
"Totus, teres, atque rotundus,"
(which may be freely translated for the occasion, "perfect, round, complete in all its parts"), it surely must, as the late lamented Professor Henfrey said, be the most numerous in individuals on the face of our globe. But it requires to be grown and watched, varying external circumstances of temperature, amount of moisture, exposure, and so on, with a good deal of ingenuity, before this can be safely affirmed.
The little "Ulva crispa," gathered last, is always a favourite object (Fig. 3) with its bright green endochrome dotted with a charmingly regular irregularity over the delicately transparent membrane of the frond. With the mature plant may often be found narrow flat threads as at h, which show in an instructive manner how a broad leaf-like expansion may be formed by repeated cell-divisions, now in a longitudinal direction and then in a transverse direction. Some of the pretty bright green cell-contents have escaped, and taken on an active animal-like existence, as at d. The specimen from which our figure was taken swarmed with them, and though we did not actually witness any of them escaping, such has been seen. Numerous Euglenæ (Fig. 4) occurred with them, of which all that can be said here is simply to stimulate inquiry; though so thoroughly animal-like in their movements, altering their shape continually as they move over the field, vibrating the little whip-like cilium or two with which they are furnished − with their little red eye-like speck, and at some stages of their existence a small vesicle dilating and contracting at intervals heart-like, yet these are now known to be only motile spores (the name given to bodies analogous to seeds produced by non-flowering plants). The stages of growth of Ulva are not yet fully known, and it seems possible that the Euglenæ forms found on this occasion with the Ulva might be motile spores of the latter. Having sought to attract to the study of these humble plants, by showing how elegant their appearance is under the microscope, how instructive the little we yet know about them, and how much of yet greater interest remains to be learnt of the history of their life, let us briefly glance at the important part borne by them in the economy of Nature. In poesy, the intensified and spiritualized reflection of the popular mind, mistaking the cause, it is held that they are pernicious in their effects.
"Mantled over with green, ― The stagnant pool,"
is a familiar representation of all that is foetid and unwholesome. But is it indeed owing to this green vegetation that such is the case ? Nay, on the contrary, the very opposite is the fact. Is there such a collection of foulness ? Borne on the four winds of heaven, at once the Oscillatoria and allied types of vegetation appear to commence their mission of usefulness to man. Look at the portion left in the watchglass : the spot where it was crowded together, a shapeless, unsightly substance, is now deserted, and instead, it has wormed its way to the extreme edges of this miniature collection of water, the ends all pointing outwards, as they would go further " 'an if they could." Even to the naked eye, it is now a pretty spectacle, the threads forming a delicate green fringe round the margin of the glass. Thus, in the pools they spread, increasing with amazing rapidity, feeding on agencies destructive to our life, oxygenating the water, and through it the air in the neighbourhood of which they grow. By their decay a soil is formed for plants of a higher type and with higher powers of usefulness. But let us, especially the dwellers in great cities, forget not how much we owe to the unthought of agencies of "that green stuff;" in revivifying the "used-up" atmosphere we are compelled by the circumstances of position to breathe, and let us not again attribute to them, our friends, ill effects which they are incessantly doing their utmost to counteract.