Plantigrade

“ That which chiefly distinguished the Palæozoic from the Secondary and Tertiary periods was its gorgeous flora. It was emphatically the period of plants,—"of herbs yielding seed after their kind." In no other age did the world ever witness such a flora: the youth of the earth was peculiarly a green and umbrageous youth,—a youth of dusk and tangled forests, of huge pines and stately araucarians, of the reed-like calamite, the tall tree-fern, the sculptured sigillaria, and the hirsute lepidodendron. ”

“ And with the first indications of land we pass direct from the Thallogens to the Acrogens,—from the sea weeds to the fern allies. The Lycopodiaceæ;, or club mosses, bear in the axils of their leaves minute circular cases, which form the receptacles of their spore-like seeds. And when, high in the Upper Silurian System, and just when preparing to quit it for the Lower Old Red Sandstone, we detect our earliest terrestrial organisms, we find that they are composed exclusively of those little spore receptacles. The number of land plants gradually increases as we ascend into the overlying system. ”

“ The plant-remains of the Lower Cretaceous greatly resemble those of the Jurassic period, consisting mainly of Ferns, Cycads, and Conifers. The Upper Cretaceous rocks, however, both in Europe and in North America, have yielded an abundant flora which resembles the existing vegetation of the globe in consisting mainly of Angiospermous Exogens and of Monocotyledons. ”

“ This order which is very generally distributed over the globe, being found in every quarter of it, and in almost every kind of soil and climate, abounds in species, but is very limited in the number of genera, the latter, standing in the proportion of only about 1 to 19 or 20 of the former, on whole order. Among its species every form of vegetation is found, from the very minute annual scarcely 3 inches high, up to large sized trees. Many of these are milky plants, with round stems, and ex-stipulate, scattered, simple, entire, sessile, leaves, or having the limb attenuated into a short petiol. ”

“ Many of the plants die every year, and prepare at the bottom a soil fit for the growth of a higher order of vegetation, Phragmites, Acorus, Sparganium, Rumex, Lythrum, Pedicularis, Spiraea, Polystichum, Comarum, Caltha, etc., etc. In the course of twenty or thirty years the muddy bottom is filled with roots of aquatic and marsh plants, which are lighter than water, and if the depth is great enough to give room for detaching this vegetable network, a couple of yard for example, it rises to the surface, bearing with it, of course, the soil formed above it by decay of stems and leaves. ”

“ From many parts of the world large collections of fossil plants have been obtained from strata referred to the Rhaetic period, or to the upper division of the Triassic system. A comparison of floras from these geological horizons in different parts of the world points to a vegetation extending from Australia, Cape Colony, and South America, to Tonkin, the south of Sweden and North America, which was characterised by a greater uniformity than is shown by widely separated floras at the present day. ”

“ Fig. 55.—Inflorescence of Plantago major, with bracts partly replaced by leaves and spike branched.
Fig. 56.—Inflorescence of Plantago lanceolata, bearing a tuft of leaves and flowers at the end of the flower-scape.
It is rather singular that each species of Plantago seems to have its own perverse mode of growth; for instance, the bracteate, polystachyate and paniculate forms are almost exclusively confined to P. major, the roseate form to P. media, the proliferous form to P. lanceolata. ”

“ With the exception of the algae and a few representatives of other classes of plants, which live in the shallow-water belt round the coast, or in inland lakes and seas, plants are confined to land-surfaces; and unless their remains are swept along by streams and embedded in sediments which are accumulating on the sea floor, the chance of their preservation is but small. The strata richest in fossil plants are often those which have been laid down on the floor of an inland lake or spread out as river-borne sediment under the waters of an estuary. ”

“ Wherever the plancton goes, there is living animation, grouping itself in closely packed colonies. The purest and most translucent salt water shows under certain luminous rays a multitude of little bodies as restless as the dust motes that dance in shafts of sunlight. These transparent beings mingled with microscopic algae and embryonic mucosities are the plancton. In its dense mass, scarcely visible to the human eye, float the siphonoforas, garlands of entities united by a transparent thread as fragile, delicate and luminous as Bohemian crystal. ”

“ After walking a mile we reached the outskirts of a vast forest, but not one of those forests of fungi which bordered Port Gräuben.
Here was the vegetation of the tertiary period in its fullest blaze of magnificence. Tall palms, belonging to species no longer living, splendid palmacites, firs, yews, cypress trees, thujas, representatives of the conifers, were linked together by a tangled network of long climbing plants. A soft carpet of moss and hepaticas luxuriously clothed the soil. ”

“ There are huge points of rock which time and nature are clothing with velvet garments of moss. Layer after layer of dust settles in the hollows, the rains beat it down, and the birds bring seeds. The tropical vegetation spreads out luxuriantly in thickets and underbrush, while curtains of interwoven vines hang from the branches of the trees and twine about their roots or spread along the ground, as if Flora were not yet satisfied but must place plant above plant. ”

“ The transportation of seeds of plants by water requires very little notice; every one is familiar with the mode in which coral islands, which gradually rise out of the sea, become covered with vegetation. "If new lands are formed, the organic forces are ever ready to cover the naked rock with life.—Lichens form the first covering of the barren {75}rocks, where afterwards lofty forest trees wave their airy summits. The successive growth of mosses, grasses, herbaceous plants and shrubs or bushes, occupies the intervening period of long but undetermined duration." ”

“ But the plantain does not grow wild, though in tropical America it finds the same conditions of vegetation as in its native country, and hence thrives there. The wild plantain in India has small stony seeds, and is distributed widely by monkeys, bats, and insects. which like the fruit but cannot destroy the seeds. In Asia wild, seed-bearing plantains are usually found growing in groups. In America, which has a much greater area of wilderness, the plantain must have spread far and wide, seeing that it has persisted in the wild state in the far more densely-inhabited East Indies. ”

“ The position of sepals and petals does not agree with that of a true 4-merous flower, which is represented in Fig. 361 E. The bracteoles are always suppressed in Plantago.
Plantago (Plantain, Rib-grass) . The foliage-leaves are most frequently scattered, entire, with curved veins, arranged in a rosette close to the ground on an unlimited rhizome; the spike-like inflorescence is borne on a long scape; in some (P. psyllium) [531] the leaves are opposite on a stem with well-developed internodes, and the inflorescences are borne in their axils. ”

“ When the vegetation is fully expanded, this marked division along the whole side of the range into two broad bands of green, the lighter below and the darker above, becomes very striking. The lighter band represents the cultivated portion of the slope, the vineyards, the farms, the orchards, covering the gentler, more gradual part of the descent; and the whole of this cultivated tract, stretching a hundred miles east and west, belongs to the Cretaceous epoch. The upper slope of the range, where the forest-growth comes in, is Jurassic. ”

“ The fossils of trees and plants, as well as reptiles, that we find in the great coal measures of the world, show that they were of large tropical growth, and this is shown not only in the temperate zone, but in the zone farther north. For ages and ages this rank growth of vegetation grew up and fell down until a great layer of vegetable matter was formed, which at a later time was covered over by other stratifications of earth material, so that these great layers of vegetable formation were hermetically sealed and pressed down by an enormous weight that increased as time went on. ”

“ When the story resumes again, we find life entering upon a fresh phase of richness and expansion. Vegetation has made great advances in the art of living out of water. While the Palæozoic plants of the coal-measures probably grew with swamp water flowing over their roots, the Mesozoic flora from its very outset included palm-like cycads and low-ground conifers that were distinctly land plants growing on soil above the water level. The lower levels of the Mesozoic land were no doubt covered by great fern brakes and shrubby bush and a kind of jungle growth of trees. ”

“ In the Upper Cretaceous, cycads become rare. The highest types of flowering plants gain a complete ascendency, and forests of modern aspect cover the continent from the Gulf of Mexico to the Arctic Ocean. Among the kinds of forest trees whose remains are found in the continental deposits of the Cretaceous are the magnolia, the myrtle, the laurel, the fig, the tulip tree, the chestnut, the oak, beech, elm, poplar, willow, birch, and maple. Forests of Eucalyptus grew along the coast of New England, and palms on the Pacific shores of British Columbia. ”

“ Chemical action.—Vegetation takes a most important part, from a chemical point of view, both in the first formation of soils and in their subsequent relations to vegetable life. The lower forms of vegetation are usually the first to take possession of rock surfaces; foremost among these are the lichens. In humid climates we find these crust-like plants incrusting more or less all exposed rock surfaces, sometimes with a solid mantle that can be peeled off in wet weather, showing the corroded rock-surface, and the beginnings of soil clustering amid the root-fibrils beneath. ”

“ Darwin records numerous silicified stems in Northern Chili, and the Uspallata Pass. In the central part of the Andes range, 7000 feet high, he describes the occurrence of “Snow-white projecting silicified columns.... They must have grown,” he adds, “in volcanic soil, and were subsequently submerged below sea-level, and covered with sedimentary beds and lava-flows [107] .” A striking example of the occurrence of numerous petrified plant stems has been described by Holmes from the Tertiary forests of the Yellowstone Park. ”

“ The orchids are mostly small or moderate-sized plants, few of them being more than a metre or so in height. All of our native species, with the exception of a few from the extreme south, grow from fibrous roots or tubers, but many tropical orchids, as is well known, are “epiphytes”; that is, they grow upon the trunks and branches of trees. One genus, Vanilla, is a twining epiphyte; the fruit of this plant furnishes the vanilla of commerce. ”

“ As we approach to the termination of the Mesozoic, which, in regard to animal life, is the age of reptiles, a new and strange development meets us. We find beds filled with leaves of broad-leaved plants similar to those of our modern woods, and in most cases apparently belonging to the same genera with plants now living, and this new type of vegetation persists to the present, though with marked differences of species in successive eras, as in the Middle and Upper Cretaceous, and the Lower, Middle and Upper Kainozoic, or Tertiary. ”

“ They consist of blue clays with some subordinate layers of lignite, and exhibit a richer flora than the overlying Newer Pliocene beds, and one receding farther from the existing vegetation of Europe. They also comprise more species common to the antecedent Miocene period. Among the genera of flowering plants, M. Gaudin enumerates pine, oak, evergreen oak, plum, plane, alder, elm, fig, laurel, maple, walnut, birch, buckthorn, hickory, sumach, sarsaparilla, sassafras, cinnamon, Glyptostrobus, Taxodium, Sequoia, Persea, Oreodaphne (Fig. 134) , Cassia, and Psoralea, and some others. ”

“ Facts of a very similar nature are offered by the succession of Plants upon the globe. Thus the vegetation of the Palæozoic period consisted principally of the lowly-organised groups of the Cryptogamous or Flowerless plants. The Mesozoic formations, up to the Chalk, are especially characterised by the naked-seeded Flowering plants—the Conifers and the Cycads; whilst the higher groups of the Angiospermous Exogens and Monocotyledons characterise the Upper Cretaceous and Tertiary rocks. ”

“ The statement is occasionally made that the numerous fossil algae and the absence of higher plants in the older strata justify the description of the oldest rocks as belonging to the ‘age of algae.’ Such an assertion rests on an unsound basis, and is rather the expression of what might be expected than what has been proved to be the case. The oldest plants with which we are at all closely acquainted are of such a type as to forcibly suggest that in the lowest fossiliferous rocks we are still very far from the sediments of that age which witnessed the dawn of plant life. ”