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· Darwin alludes to these emigrations in the following manner:
Where vast Ontario rolls his brineless tides,
And bears to Norway's coasts her infant loves. Some plants float from one end of the globe to the other. The trumpet-grass, seen off the Cape, is torn, for the most part, from the South African shores; but others are wafted from the American continent. The pistia straliotes float on pools, ditches, and rivers in Java. Its root takes but little or no hold of the ground. The marine weeds, that compose the grassy sea in the Atlantic, have neither roots nor fibres a. They vegetate, as they float along, bearing green and red berries, harbouring a multitude of insects. There is also a plant in Chili b, and a similar one in Japan, called the “ flower of the air.” This appellation is given to it, because it has no root, and is never fixed to the earth. It twines round a dry tree, or sterile rock. Each shoot produces two or three flowers like a lily; white, transparent, and odoriferous. It is capable of being transported two or three hundred leagues ; and it vegetates as it travels, suspended on · a twig.
Many plants have a double faculty of propagation. The testuca ovina has this property. When it grows in a vale, or upon a plain, its seeds ripen, fall, and vegetate in the manner of other plants. But when it grows upon the tops of mountains, where it finds a difficulty in ripening its seeds, it becomes a viviparous plant. The germ shoots into blade in the cup; falls to the ground; takes root; and becomes the mother of others, having the same remarkable property. The aphis (insect) is also viviparous in summer, and oviparous in autumn.
a Sea-weeds generally propagate from roots.
o Molina, i. p. 316, in notis. .
Some seeds are thrown by the force of the surf, which, in some places, rises even to the height of ten fathoms. Lifted so high in air, the winds separate them, as they descend, from the particles of water, with which they rose, and waft them to the internal parts of the island. Some plants in the Pacific islands were probably originally marine. Cast upon the shore, they have vegetated : these have produced seeds, which, being carried by winds or birds higher from the sea, have accommodated themselves to the soil, in which they were thus accidentally thrown; and during a series of propagations have gradually assumed characters not originally belonging to them. The nymphæa alba has, in this way, been the patriarch of many plants, now differing in shape and habit from itself. This vegetable, like many other aquatic plants, at the time of flowering, rises to the surface of the water: in the morning it expands its blossoms, and towards evening closes them again.
Many trees, such as the oak, beech, and hazel, are planted by squirrels and ravens; and the cinnamon of Ceylon and Malabar are propagated by the Pompadour pigeon; which drops the fruit, as it is carrying it to its young. The doves of Banda swallow seeds whole, and expel them whole ; and in this manner propagate the nutmeg. The missel lives on the berries of the misseltoe, and propagates it from tree to tree.
Some weeds are disseminated by the winds; as mosses, fungi, and mucor. The leather-cup has a seed so small, that it is almost imperceptible. This, and many seeds of similar minuteness, are conveyed in the leaves and trunks of trees. Some are fixed by the winds to the coats of animals; the feathers of birds ; the sides of ships ; and others to the backs of insects. Some seeds have species of feathers, which enable them to be sustained in the atmosphere to a great distance. The roridula dentata has leaves covered with fine hairs, and a glutinous substance, to which small insects adhere; and their eggs are, in consequence, wafted to wherever that plant is carried.
Some animals are wafted by the drifting of canoes. In desert islands, where there are no quadrupeds but rats, fragments of canoes have been observed, stranded on the shores. Those canoes were probably the media, by which those animals were conveyed. Many vegetables of the Friendly and Society adorn the Sandwich Islands ; though many leagues distant. Islands, situate from the 50th to the 55th degree of latitude, have the same beasts, birds, fishes, and shells, that are found upon the Kurili Islands : and those, from the 55th to the 60th degree of latitude a, have many animals that are found on the peninsula of Kamschatka.
Bears, foxes, ermines, seals, and walruses; wild fowl ; the spawn of river-fish, and the eggs of northern birds, are car- . ried to distant longitudes and latitudes by ice islands. Of these islands there are two species ;--one composed of sea water ; the other of fresh water. The former kinds are white, and have little transparency: the latter blue, and so clear, that objects may be seen to a considerable depth. These are mostly formed on the sides of rocks, jutting over seas or large rivers. They melt in summer, at the lower extremities, by the influence of the sun, and the moisture of the waves below. Thus undermined, their bulk becomes too ponderous for their base : they break; and, falling into the river or sea, float; and being joined by others, unite and form themselves into islands of vast length, breadth and height: And not unfre. quently sail with the winds, currents, and tides, from the arctic circle to the utmost extremity of the temperate zone;exhibiting, as they sail along, upon a minute survey, innumerable combinations-occasioned by the spray of the sea,
* Vide Stæhlius' Account of the New Northern Archipelago, p. 18.
the mists, and the snows,—of trees, and flowers ; villages, towns, and cities ; ruins, and palaces ; and myriads of forms before unknown, even to the imagination.
The mountains of ice, which are composed of fresh water, are not unfrequently incorporated with soil, stones, and brushwood; and covered with the eggs of those birds, which frequent the coasts, from which they fall“. The salt water islands bear sea weeds, spawn, and not unfrequently bears, foxes, and ermines. In the north of Iceland b, the cold splits the calcined mountains, from which large masses fall in detached pieces, and roll precipitately into the sea, like waterfalls.
The approach of ice islands is indicated by the bluish lustre, which appears in the horizon. They are often covered, too, with an immense number of seals and sea calves ; which are seen rolling and sporting in the snow, and seem by no means terrified at the approach of either men or ships : reminding the voyager of those lines of Cowper, which he puts into the mouth of Alexander Selkirk,
The beasts, that roam over the plain,
My form with indifference see :
Their tameness is shocking to me.
Professor Smith saw several islands, floating from the African rivers, which, upon inspection, he found to bear reeds, resembling the donax, a species of agrostis, and some branches of justicia, with the roots of mangrove and papyrus. There were, also, in the midst of them, several small animals; which are found, also, floating on the Grassy Sea".
Reptiles are probably propagated to distant regions by their eggs, or embryos, being casually dropt on the sea shore, at low ebb, and borne away by the returning tides. Some insects are transported on the backs, and in the intestines of animals : others in their skins. The hair-worm lives not only in the earth, on the leaves of trees, and in the water, but in the bodies of beetles : while large flies enter the ears of elks, in the Lapland forests; and take up their winter quarters in their heads.
a In one of the Dutch voyages to Nova Zembla, the captain ascended an iceberg, on the top of which were a considerable quantity of earth, and forty birds' eggs.
Freminville, Voyage to the North Pole, p. 12.
c Journal-Tuckey, p. 259. • Scyllæa Pelagica.-Cancer minutus.-Lophius histrio, &c. &c.
Vipers are easy of transportation; since they possess such a faculty of abstinence, that some species will remain even six months without food. Canadian bears, also, frequently live without sustenance so long, that many persons believe, they can live by licking their own paws.
. It is exceedingly curious, that in Ireland there is neither a mole, a spider, nor any venomous reptile or insect. Frogs, a hundred years ago, were foreign to Ireland; but having been observed, for the first time, in a well at Moira, in the county of Down, they have multiplied all over the island. How came they into that well ? There are no frogs in Laplanda; nor, I believe, in Iceland ; but in 1783, the pastures of that island abounded in small insects, which had never been seen there before. They resembled ", in some degree, the earthfly; blue, red, yellow, and brown. The weevil, in the same manner, will not live in Van Diemen's Land : in which island grows the cedar (huon pine), which has the property of repelling insects. The cochineal has been found extremely difficult to transplant: and it is remarkable, that though insects are the most liable to corruption of all animals, the cochineal never spoils. It has, therefore, been preserved for ages.
The spawn of some fishes are propagated by insects and aquatic birds : some of which even void the fishes, they have gorged, without any change in the fishes themselves. Eels · Lachesis Lapponica, i. 177.
b Hooker, ii. 5. c The large water-beetle feeds on spawn. It rises on the leaves of the water-plants, and takes wing. By this insect mountain lakes are frequently stocked.