And swells, and deepens, to the cherish'd eye. By Nature's swift and secret-working hand, Within its crimson folds. Now from the town, Where freshness breathes, and dash the trembling drops Or taste the smell of dairy; or ascend One boundless blush, one white-empurpled shower 111 bounteously clothed in green, not only as it affords the most pleasing sensation of all the colours, but also because it is essential for preserving the eye in that condition which is requisite for the various purposes of vision. * The most ancient name of London was Tri-now, or the New City; it was founded by the Trinobantes, of whose kingdom, now comprising Essex, Middlesex, and part of Surrey, it was the capital. After the Roman conquest it became a place of great trade, wealth, and grandeur, on which account the Romans called it Augusta.— Henry's Hist. of Britain, vol. i. p. 170. If, brush'd from Russian wilds, a cutting gale 115 *The poet has, in this instance, fallen into the vulgar error that the mildew depends upon fogs or noxious exhalations, whereas it really depends on several kinds of parasitic fungi; the sporules of which find a fit soil for vegetating on weak and unhealthy plants: but are seldom found on the strong and healthy. The sudden appearance of some of these parasites, in humid states of the atmosphere, occurring after long drought, has given rise to the mistake that they are actually brought by the winds which prevail in that kind of weather. Thus we find the whiteness which covers the leaves and young shoots of roses, and which is a parasite (Acrosporium monilioides), consisting of a congeries of necklacelike filaments, appearing in one night; and the same suddenness of appearance occurs in another species of mildew, which chiefly attacks peas, namely, the Erysiphe communis of Linnæus. In all such cases, the parasite dips its roots into the leaf and succulent green stem, and abstracts the nourishment of the plant. The employment of the epithet "clammy" by the poet induces me to believe that he refers rather to the honey-dew (Suffusio mellita) than the mildew; and I am confirmed in this opinion from the mildews not appearing in spring, but towards autumn, whereas the honey-dew prevails in spring. It is a viscid juice that appears on the upper surfaces of leaves, like spots of varnish; it is clammy, and has a sweet taste. Some writers suppose that it depends on the puncture of the leaves by the aphis or green plant-louse, and the deposition of the sap, rendered sweet in its passage through the body of the insect, on the upper surface of the leaves, below those on which the aphides congregate on the under surface; but there is more reason for believing that it is a morbid secretion of the leaf itself, in very hot and dry weather. Duhamel says, that he has observed it in such abundance on willows by the side of a river that it dropped from the points of the leaves, and children were busy in catching it. I am inclined to adopt this explanation, as I have seen it on leaves where no aphides were present. In Syria, the honeydew, which forms in great quantity, is allowed to drop from the trees and harden into globules, which are afterwards dissolved in water and used as drink. †The vernal frosts in this country, when accompanied with east or north-east winds, are extremely injurious to vegetation; whilst the ordinary frosts, without wind, are much less hurtful. 1 Physique des Arbres, i. p. 150. The full-blown Spring through all her foliage shrinks, Joyless and dead, a wide-dejected waste. The former cause a greater evaporation from the surfaces of the leaves than the absorbing powers of the plant are able to supply with moisture; which dries the leaves so much, that they are easily reduced to powder if rubbed between the fingers: the latter only hurts by the cold, which can be resisted to a great degree, by plants as well as by animals. But the most pernicious kind of frost is hoar frost, and especially that which immediately succeeds wet or foggy weather; for then the leaves and succulent parts of plants are full of moisture, the expansion of which, in freezing, tears asunder and destroys the delicate tissue of the leaves and blossoms. Trees and plants, growing in valleys and places seemingly sheltered, often suffer more from vernal frosts than those that are on elevated and exposed situations; and we find that elevated grounds escape the effects of hoar frost, while low grounds suffer. Plants, as well as animals, however, possess an innate conservative power of resisting cold to a certain extent; for were this not the case, every vegetable body would require to be renewed, annually, after the devastations of winter. The necessity of the power of maintaining a temperature greater than that which freezes water is demonstrated by other facts besides their actual temperature as measured by the thermometer. Thus, it has been clearly ascertained, that vegetation is not at perfect rest during winter: it is only more languid than in summer. The roots of trees absorb fluids from the soil in that season; and it is well known that those planted in the autumn are turgid with sap during winter. It is even said that a flow of sap has been procured from certain trees in mid-winter. Now, were there no power in plants to resist external cold, and retain their innate temperature, the sap, in such trees, would be frozen, and the trees inevitably destroyed, which is not the case. It is, however, true that all the parts of perennial plants are solidified, to a certain extent, in the latter end of autumn; hence, as the evaporation is greatly diminished, the roots act feebly, and only in a degree sufficient to maintain the slow ascent of the sap demanded for preserving the vitality of the plant in winter. Wall trees may be easily defended from the influence of frost by so simple and imperfect a covering as a double net, or coarse open canvass. Gardeners often cover trees and shrubs with mats, or some other close wrought substance," and by almost totally depriving the tree of light, create," says Mr. Knight, "that blight which they are anxious to exclude." Flooding meadows protects 1 This fact is given on the authority of M. Biot. 2 Hunter's Georgical Essays, vol. iv. p. 369. For oft, engender'd by the hazy north, Keen in the poison'd breeze; and wasteful eat, 120 them from the destructive influence of frost; but when they are covered with ice, the water should be drawn off. * The description of the phenomenon alluded to in these lines of the poet, is not founded on accurate observation; and it is one of the numerous errors that have been perpetuated merely from want of investigation. The appearance of insects, in myriads, in spring, is readily accounted for without the agency of "the hazy north." Their eggs are usually laid in those places in which the larvæ are most likely to find suitable food; and, when the winter has not been sufficiently severe to destroy the eggs, the larvæ come forth at the same time, in prodigious numbers, when circumstances concur favourable to the hatching of the eggs in spring. All the insects found upon plants in Great Britain, with the exception of the Aphides, or green plant lice, which are larviparous as well as, at one period, oviparous, are produced from eggs. The greater number of butterflies and moths attach their eggs to the under surface of leaves, and to twigs and stems of plants; the eggs are usually arranged in clusters or groups on the same plant, or on different plants; and, in some instances, the arrangement is most beautiful and skilful. Thus, the lackey moth (Lasiocampa Neustrias), one of those insects whose eggs are laid in autumn to be hatched in the following spring, disposes them in numerous circles round twigs, like rings of minute pearls, each bracelet consisting of 200 to 300 eggs. They are of an elegant form. Some insects, again, deposit each egg singly, and glue it to the underside of a leaf. In many instances, also, the eggs are covered with a kind of varnish, resembling the colour of the leaf, which is intended rather to secure them from the attacks of birds and other insects than from cold but it is, also, a well-known fact that the vitality of the eggs of insects is greater than that of the pupa; and, on this account, they resist the influence of severe cold more decidedly than the pupa. The eggs of insects are hatched by atmospheric heat; the influence of temperature, in this process, is strikingly demonstrated by the fact, that not only are the eggs laid in summer hatched in a few days, but those laid in autumn, and intended to be preserved through the winter, are hatched when brought into a warm room. But, besides the hatching of myriads of the eggs of insects in early spring, the fecundity of some of them is almost incredible; one The sacred sons of vengeance! on whose course 125 female Aphis, says M. Latreille, will produce twenty young ones in one day; and during its life, says M. Reaumur, it may be the progenitor of 5,904,900,000 descendants. Another source of the myriads of insects, at that season, is their awaking from their hybernation or winter sleep, which occurs at a much lower temperature than that at which they become torpid. We must not, however, as Kirby properly argues, ascribe the retreat of insects to their winter habitations or hybernacula to cold, but to that unerring instinct which regulates most of their actions. After these remarks, we can have no difficulty in accounting for the myriads of insects that appear in spring without the necessity of tracing their coming to peculiar winds. The insects to which the poet chiefly alludes are those which infest our fruit trees. The larva of a Saw-fly (Tenthredo Cerasi) feeds upon the leaves of the cherry tree. The pear tree suffers from the ravages of the same insect; and, also, from another which deposits its egg in the embryon fruit, and causes it to drop prematurely from the tree. The figure-of-eight moth (Bombyx cæruleocephala) is a destructive enemy of the apple tree; and Mr. Kirby informs us, on the authority of Mr. Scales, that hundreds of young grafts of apple trees are frequently destroyed in one night in the nurseries around London, by a short-snouted weevil (Curculio vastator). But the greatest plague which can alight upon the apple tree is the American blight, or apple aphis (Aphis lanigera). "This," says Mr. Kirby, is a minute insect, covered with a long cotton-like wool transpiring from the pores of its body: it takes its station in the chinks and rugosities of the bark, where it increases abundantly and, by constantly drawing out the sap, causes ultimately the destruction of the tree.". "At first the depredations of this insect were confined to the vicinity of the metropolis, where it destroyed thousands of trees: but it has now found its way into other parts of the kingdom, particularly into the cider counties; and, in 1810, so many trees perished from it in Glocestershire, that, if some mode of destroying it were not discovered, it was feared the making of cider must be abandoned. "1 66 The Aphides are great enemies to the plum; and a Coccus (C. Persica) often abounds upon the trees to such an extent "that every twig is beaded with the red semiglobose bodies of the gravid females, whose progeny in spring exhausts the trees by pumping out the sap. Many methods have been devised to check the ravages of these "feeble," but voracious, enemies of the orchard. Sir Joseph Banks 1 Kirby and Spence's Introd. to Entomology, vol. i. p. 201. 2 Ibid. vol. i. p. 199. |