MINUTE PLANTS.

As we have vegetables celebrated for their gigantic size, so we have others remarkable for the minuteness and delicacy of their proportions. Nature knows no limit either in the ascending or descending scale: she is as wonderful and perfect in the formation of a fungus, which the unassisted eye cannot detect, as she is in the structure of the oak and cedar, which command our veneration. With the characters of the latter the botanist has been long familiar, because their dimensions more forcibly arrest the eye of sense; to the structure of the former he is only beginning, as it were, to have access through the lenses of the microscope.

One of the most extraordinary of microscopic plants is the Achlya prolifera, whose soft silky threads may sometimes be seen adhering to the surface of gold-fishes, and covering them, as it were, with a whitish slime. This appearance is generally looked upon as a species of decay or consumption in the animal itself, and not as an external clothing of parasitic plants. It is, however, a true vegetable growth, each individual consisting of a single filament, with a minute pear-shaped ball on the top, containing numerous grains, which are the seeds or embryos of future plants. The green slime, which in summer gathers over the surface of stagnant water, is of the same order of vegetation; namely, Conferva-an order entirely dependent upon water for their growth and propagation, and to which drought is certainly fatal. The achlya has been examined by Dr Unger, who describes it, when at its full growth, as consisting of transparent threads of extreme fineness, packed together as closely as the pile of velvet, and much resembling, in general appearance, certain kinds of mouldiness. When placed under the microscope-for the unassisted eye can perceive nothing of its true construction-each thread is terminated by the pear-shaped ball already alluded to, which is about 1-1200th of an inch in diameter, and consists of a single cell filled with a mucilaginous fluid, in which float the procreative granules. The contents of this cell are seen to be in constant motion from the earliest stage of their existence; but as they advance to maturity, the mucilage disappears, and then the motion of the granules becomes more rapid and violent, till ultimately they burst their way through the cell, and are transferred to the water, there to perform their circle of being, and to give birth to new races of granules. All this takes place with such amazing rapidity, that we are assured an hour or two suffices for the complete development and escape of the spores; so that we need not wonder when we are told that, once established, the Achlya prolifera will often complete the destruction of a healthy gold-fish in less than twelve hours.

Another of these curious parasites is the Mucor mucedo, which

abounds in bruised fruit and other substances containing fecula or sugar. It belongs to that section of the fungi generally known under the name of moulds, of which that common on stale bread, and the rust, mildew, and smut in wheat, are familiar examples. These moulds are of all shapes-simple, branched, spherical, radiating, presenting a surface like velvet, or a net-work of the most delicate texture;, and of all hues-green, blue, yellow, and vermilion. The Mucor mucedo consists of a single filament, headed by a very minute ball-shaped receptacle. In the young state, this little ball is covered by a thin membrane, which bursts as the spores arrive at maturity, which then present themselves like so many dusty particles congregated round a central nucleus. Being so minute, the slightest touch or the gentlest breath of air is sufficient to scatter them in thousands; and thus the mucors increase with amazing rapidity. As they require abundant nutriment, it is only on succulent parts that they luxuriate, and for this reason they are principally injurious to fruits-the slightest injury from an insect affording them a basis for propagation.

Mucor mucedo, highly magnified.

From the examples we have just given, it must not be supposed that plants of microscopic dimensions are to be found only among parasitic fungi. There are others equally minute, and still more wonderful in the aggregate, which are of independent growth, and which twine and interlace their tiny branches into a net-work as tough as the strongest felt, and extending over many yards of surface. These are the fresh-water confervæ, of which the substance called 'water-flannel' may be taken as a well-known example. A specimen was thus described by a correspondent of the Gardeners Chronicle: A friend put into my hand the other day a yard or two of what seemed a coarse kind of flannel, gray on one side, and greenish on the other, and a full quarter of an inch in thickness. It had been thrown up by the river Trent, and washed ashore in vast sheets. Those who had seen it pronounced it a manufactured article; and so it was, but by the hand of nature. When this substance is handled, it is harsh to the touch, although composed of the finest threads. To the naked eye, it presents no character by which it may be known from any coarse and loosely-woven cloth. The microscope reveals its nature. It is then found to consist of myriads of jointed threads, whose joints are compressed alternately sideways and vertically; they are here and there transparent, but for the most part opaque and rough to the eye. The white side is more opaque than the other, and more unexaminable; but if a little muriatic acid be added to the water in which the fragments of water-flannel float, copious bubbles of air appear. These are bubbles of carbonic acid,

extricated by the action of the muriatic acid on a coating of carbonate of lime, with which the plant is more or less completely invested. If, after this operation, the threads are again examined, the contents of the joints become visible: in the green parts of the flannel, they were filled with an irregular mass of green matter; in the white part, with myriads of globules, intermixed with a shapeless substance. The globules are the seeds. If a little iodine is then given to the flannel, it is readily absorbed; and the contents, shapeless matter, globules, and all, become deep violet, shewing that all this substance is starch. Hence it appears that the water-flannel is a microscopic plant, composed of jointed threads, secreting carbonate of lime on their surface, and forming seeds composed of starch within them. And when we consider that the joints are smaller than the eye can detect, while each contains from fifty to one hundred seeds, it may easily be conceived with what rapidity such a plant is multiplied. Besides which, as their contents consist to a great extent of starch, the most readily organisable of vegetable materials, the means of growth with which the plant is provided are far more ample than anything we know of in the higher orders of the vegetable kingdom.' This vegetable swarms on stagnant pools, where it lives on the decaying matter which all waters more or less contain, and thus tends to their purification, the while that its own substance forms food for myriads of animalcules that wander over its trackless fields and endless mazes.

Here, however, we must close our record of microscopic plants, which, it will be seen, belong chiefly to the mosses, lichens, fungi, and other forms of flowerless vegetation. Zoologists tell us, when speaking of animalcules, that there is not a drop of stagnant water, not a speck of vegetable or animal tissue, but has its own appropriate inhabitants. The same may be remarked of plants; for we cannot point to a speck of surface, unless chilled by everlasting cold, or parched by continuous drought, that has not its own peculiar vegetation. The spores or seeds of these minute parasites are almost infinitesimally small: they are floating above and around us, unperceived by the naked eye, ready to fall and germinate wherever fitting conditions are presented. Nay, as certain changes in animal tissue are ascribed to animalcules, certain changes in organised substances, such as fermentation, are ascribed to vegetable growth. Yeast is a true vegetable, consisting of minute organised cells or spherules, which propagate with amazing rapidity so long as they find their proper nutriment in the fermenting liquid. Nor is there anything more incredible in the fact, that the little globular yeastplant should extract its nutriment from the fluid on which it floats, than that the water-flannel should extract its starch or lime from the water which it covers.

PECULIAR PLANTS.

Under this head we comprehend such plants as stand out in bold relief from the rest of the vegetable kingdom for some noted peculiarity in structure, habits, or properties. It is true that every plant has its own specific distinctions; but there are several which seem to stand apart as the curiosities of vegetation, just as the ornithorhyncus and giraffe stand isolated among animals. They have no congeners in the peculiarity that renders them remarkable.

The cow-tree, or palo de vaca of South America, is one of the most interesting of this class. It is known to botanists as the Galactodendron utile, or useful milk-tree, and belongs to the Urticacea, or nettle tribe, the herbaceous members of which have their juice thin and watery, while in the ligneous species it is milky and viscous.. The cow-tree is a native of the Caraccas, and grows in rocky situations at an elevation of nearly 3000 feet. It is thus described by Baron Humboldt: On the barren flank of a rock grows a tree with. dry and leathery leaves; its large woody roots can scarcely penetrate into the stony soil. For several months in the year not a singleshower moistens its foliage. Its branches appear dead and dried; yet, as soon as the trunk is pierced, there flows from it a sweet and nourishing milk. It is at sunrise that this vegetable fountain is most abundant. The natives are then to be seen hastening from all quarters, furnished with large bowls to receive the milk, which grows yellow, and thickens at the surface. Some drain their bowls under the tree, while others carry home the juice to their children; and you might fancy you saw the family of a cowherd gathering around him, and receiving from him the produce of his kine. The milk obtained by incisions made in the trunk is glutinous, tolerably thick, free from all acridity, and of an agreeable and balmy smell. It was offered to us in the shell of the trituros or calabash tree. We drank a considerable quantity of it in the evening before going to bed, and very early in the morning, without experiencing the slightest injurious effect. The viscosity of the milk is the only thing that renders it somewhat disagreeable. The negroes and free labourers drink it, dipping into it their maize or cassava bread.' Sir R. Ker Porter describes the palo de vaca as a tree of large dimensions, mentioning that he measured one somewhat more than 20 feet in circumference at about 5 feet from the root. This colossal stem ran up to the height of 60 feet perfectly uninterrupted by either leaf or branch, when its vast arms and minor branches, most luxuriantly clothed with foliage, spread on every side fully 25 or 30 feet from the trunk, and rose to an additional height of 40 feet, so that this stupendous tree was quite 100 feet high in all. Others were seen at a distance of still larger dimensions.

Equal in utility with the cow-tree in yielding an agreeable

beverage, but belonging to a very different order, is the ravanala, or traveller's tree of Madagascar. This curious plant belongs to the same tribe as the plantain and banana; namely, the Musacea, and is known to botanists by the name of Urania speciosa. It forms a striking feature in the scenery, as it does in the economy of its native country, and is thus described by Mr Backhouse in his Visit to the Mauritius and South Africa: Clumps of these trees, composed of several stems rising from the same root, are scattered over the country in all directions. The trunks, or, more properly, root-stocks, which are about 3 feet in circumference, sometimes attain to 30 feet in height; but whether of this elevation, or scarcely emerging above ground, they support grand crests of leaves of about 4 feet long and I foot wide, but often torn into comb-like shreds. The head is of a fan-like form, and the flowers, which are not striking for their beauty, are white, and produced from large horizontal green sheaths. The foot-stalks of the leaves, which are somewhat shorter than the leaves themselves, yield a copious supply of fresh water, very grateful to the traveller, on having their margin cut away near to the base, or forced from contact with those immediately above them, especially those about the middle of the series. The root-stock is of a soft cellular substance, and the fruit, which resembles a small banana, is dry, and not edible. This remarkable vegetable production is said to grow in the most arid countries, and thus to be provided for the refreshment of man in a dry and thirsty land. Probably the water may originate in the condensation of dew, and be collected and retained by the peculiar structure of the leaf: it has a slight taste of the tree, but is not disagreeable.'

The Pitcher-Plant, or Ñepenthes distillatoria, is another of those fluid-containing plants whose structure and adaptation strike us with wonder and admiration. It is the type of the recently established order Nepenthacea, and is commonly met with in Ceylon and other islands of the East, where it is known by the appropriate name of pitcher-plant, on account of the singular flagon-shaped appendage which holds the water. Being the inhabitant of a tropical climate,' says Barrow in his Cochin-China, 'and found on the most dry and stony situations, nature has furnished it with the means of an ample supply of moisture, without which it would have withered and perished. To the foot-stalk of each leaf, near the base, is attached a kind of bag, shaped like a pitcher, of the same consistency and colour as the leaf in the early stage of its growth, but changing with age to a reddish purple. It is girt round with an oblique band or hoop, and covered with a lid neatly fitted, and movable on a kind of hinge or strong fibre, which, passing over the handle, connects the vessel with the leaf. By the shrinking or contracting of this fibre, the lid is drawn open whenever the weather is showery or dew falls, which would appear to be just the contrary of what usually happens in nature, though the contraction probably is occasioned by the hot,