It seems advisable to begin our investigation with the vegetable kingdom, as its classification being comparatively simple, the essential points of its development are easily followed. We cannot do better than start with the summary of its main divisions furnished by Mr. Carruthers.[248]
The vegetable kingdom is divided into sections, according to the simplicity or complexity of structure. Associated with plants of simple structure we find, as a rule, more elementary organs of reproduction. Linnaeus made two great divisions, of flowering (Phanerogams) and flowerless plants (Cryptogams).... The higher group have flowers, with their stamens and pistils, which produce seeds, while the lower group are without flowers and bear spores, which are much simpler bodies than seeds. There are seven main groups of spore-bearers—the algæ or water-weeds; the fungi or mushroom family; the lichens, which cover old walls and rocks with patches of coloured vegetation; the mosses with their green leaves and urn-shaped fruit; the ferns with[{215}] their large and usually much-divided leaves, on the back or edges of which the spores are borne; the horsetails, found in wet places, having jointed hollow stems and spores produced in little cones; and the club-mosses, upright or creeping leafy plants found on our mountains. These seven groups may be arranged in two divisions, according to the tissues of which they are formed. In the first four the whole plant is composed of cells, while in the last three a firm vascular skeleton is present. These characters are of great importance to the student of fossil plants.... The flowering plants are more complex in their structure, and in their organs of reproduction. The lowest group of these plants is the Gymnosperms, or naked-seeded plants, like our yews and pines. The other flowering plants (Angiosperms) have their seeds in a closed fruit. These are divided into two sections from characters derived from the embryo plant in the seed, depending on whether this minute plant has one seed-leaf (cotyledon) or two, and so we have Monocotyledons and Dicotyledons. The higher group, or dicotyledons, have been arranged into three divisions, according to the complexity of the flower. In one large group (Apetalae) the pistil and stamens are not surrounded by petals, e.g. in the oak and the stinging nettle: superior to them are the plants (Monopetalae) in which the petals form a cup, as the blue-bell[249] and the gentian, while the highest group (Polypetalae) have all the petals separate, as the buttercups and roses.[250]
It is most important to recollect that on evolutionary principles the first representatives of any such classes—and the same holds of animals as well—must have been generalized forms, representing the type in the rough, or, in Mr. Herbert Spencer's phrase, exhibiting by comparison with their successors indefinite incoherent homogeneity, as contrasted with definite coherent heterogeneity. They should bear the same sort of relation to the finished articles worked up by Evolution as did the first bone-shaker bicycle to our latest patterns, or the news-sheets of Cromwell's time to the Times or Graphic of to-day. On this, as we saw in the last chapter, Mr. Darwin strongly insists, confessing at the same time that the Geological record alone can establish such progress as a fact.
How these various classes of plants appear actually to have come upon the scene, Mr. Carruthers relates both in the paper from which we have just quoted, and at greater length in the address which he delivered as President of the Geologists' Association,[251] to the following effect.
In the first place, he declares that although the geological record, at least as known to us, is very imperfect, and represents only an insignificant fragment of plant-history,
There is a large series of plant-remains completely[{217}] and accurately known which supply a fair representation of the great events of plant-life that have taken place on the earth since Palæozoic times. And these are more than sufficient to establish or destroy this hypothesis [of genetic evolution] by their testimony.
There is—he goes on to say—indirect evidence of the existence of vegetable life, long before we find any actual remains. Such indirect evidence is afforded in the first place by the abundance during this period of animal life, needing plants for its sustenance, and secondly by the enormous quantity of carbon in the rocks, which must have been secreted from the atmosphere by vegetable tissues. There are also certain surface marks or impressions occasionally to be found, which are probably due to plants of a soft and perishable character like the cellular cryptogams, and which although extremely vague and undefined, at least do not contradict the evolutionist, who regards them as evidence that the Algæ were, as according to him they ought to have been, the primeval plants. Mr. Carruthers adds a caution however, which can find its application in other instances as well:
While making this admission in relation to the vegetation of these older rocks, I must protest against the practice of completing the record of life forms, by filling in particular groups without any authority except the writer's impression of an adopted hypothesis, and then basing arguments on these assumptions in support of the hypothesis which created them. So completely has
