25th.—We were talking to-day about the impressions of plants perceptible in coal, and I asked my uncle to tell me what plants they were; he referred me to Miss Perceval, who says that it appears from the researches of several German botanists, and particularly from those of Dr. Martius, that some of the Brazilian plants, which are so familiar to us, dear mamma, seem to have such a resemblance to those impressions, that there can be scarcely a doubt of their identity.
“The tree ferns,” she said, “exhibit several characters in common with those ancient plants; one species in particular, the stem of which having a remarkable tessellated or chequered appearance, exactly represents some of the petrified forms found in the German coal mines. Dr. Martius describes ten different kinds of fern found in coal, each distinctly marked by some of those peculiarities which distinguish the living plants.
“As very numerous examples of the arborescent as well as the herbaceous ferns occur in the coal formation, it can scarcely be doubted that this order of plants was formerly much more numerous than it is now; and that the forests of the primitive world were abundantly stocked with them.”
“That is the more probable,” said my uncle, “as there is reason to suppose that ferns were among the first plants that spread over the surface of the globe, and that they were the basis of a more general vegetation, by preparing the ground for others. Their large fronds probably deriving as much nourishment from the atmosphere as from the earth; while their annual decay rapidly increases or improves the productive soil.”
“I do not mean, however,” said Miss Perceval, “that the antediluvian woods consisted entirely of ferns; for the remains of many other plants, and of some large trees, are found mixed with those of fern—just as the living woods of the equinoctial regions, though very rich in ferns, consist of a great variety of plants of all sizes. Several specimens of palms, and of bambusæ, have been discovered; and the cactus is another tribe which appears very abundantly amongst these petrifactions.”
“And I believe,” said my uncle, “that the remark I made respecting ferns may be repeated of those tribes,—that they are furnished with a singular structure of organs adapted for respiration, and thereby for inhaling nutritious juices from the atmosphere.”
“Yes,” said Miss P., “Saussure found that a single leaf of the cactus opuntia inhaled four cubic inches of oxygen in the course of a night from the atmospheric air in a glass vessel, in which he inclosed it; and we may, therefore, consider those tribes, and the yuccæ, and lychnophoræ, which flourish in a dry sandy soil, as the pioneers of vegetation, and intended by Nature to inhabit the rude wastes of a new world.”
After some further conversation on this subject my uncle said, “As the delicate parts of any vegetable substances would be entirely destroyed if transported to a great distance by floods, it is evident, that those plants, whose remains are found well preserved in a fossil state, must have been inhabitants of the countries where the strata were formed. This consideration has given rise to many interesting speculations on the former climate of Europe, and its apparent changes; but if mammoths and elephants were clothed with fur to enable them to endure a Siberian winter, why may we not suppose that there were also species of palms and tree ferns suited to our temperate regions? Another curious inference may be drawn from the examination of vegetable remains: those found in what the German mineralogists call brown coal, exhibit in their wood, in their fruit, and their leaves, sufficient proofs of their belonging to indigenous, or, at least, to modern races of plants; while those which occur in what is termed black coal are all unknown or exotic: there can be no doubt, therefore, that those two coal formations belong to two very different ages of the globe.”
26th.—I still find a great deal of amusement in watching my little family of swallows. They are unwearied in collecting food for their young; skimming through the air from morning till night, and darting on their prey with the most sudden turns. They catch gnats and flies, and consume an astonishing number of mischievous grubs; and I am told they often accompany people on horseback, through the fields, in order to pick up the flies which are roused from the turf by the horses’ feet.
They never touch seeds; insects are their only object, and according to the weather, or the degree of warmth, they sometimes skim along the surface of the ground, and sometimes fly at a great height. When there is a scarcity of insects they have been known to snatch the flies imprisoned in a spider’s web, and sometimes even the spider itself.