Ancient Plants / Being a Simple Account of the past Vegetation of the Earth and of the Recent Important Discoveries Made in This Realm of Nature

by Marie Carmichael Stopes

Recent work, which has carefully sifted the fossil evidence, can only say that no true Monocotyledons have yet been found below the Lower Cretaceous rocks, and that at that period we see also the sudden inrush of Dicotyledons. Hence, so far as palæontology can show, the two parallel groups of the flowering plants arose about the same time. It is of interest to note, however, that the only petrifaction of a flower known from any part of the world is an ovary which seems to be that of one of the Liliaceæ. In the same nodules, however, there are several specimens of Dicotyledonous woods, so that it does not throw any light on the question of priority.

With the evidence derived from the comparative study of the anatomy of recent flowering plants we cannot concern ourselves here, beyond noting that the results weigh in favour of the Dicotyledons as being the more primitive, though not necessarily developed much earlier in point of time. Until very much more is discovered than is yet known of the origin of the flowering plants as a whole, it is impossible to come to a more definite conclusion about this much-discussed subject.

Let us now attempt to picture the vegetable communities since the appearance of the flowering plants. The facts which form the bases of the following conceptions have been gathered from many lands by numerous workers in the field of fossil botany, from scattered plant remains such as have been described.

When the flowering plants were heralded in they appeared in large numbers, and already by the Cretaceous period there were very many different species. Of these a number seem to belong to genera which are still living, and many of them are extremely like living species. It would be wearisome and of little value to give a list of all the recorded species from this period, but a few of the commoner ones may be mentioned to illustrate the nature of the plants then flourishing.

Several species of Quercus (the Oak) appeared early, particularly Quercus Ilex; leaves of the Juglandaceæ (Walnut family) were very common, and among the Tertiary fossils appear its fruits. Both Populus (the Poplar) and Salix (the Willow) date from the early rocks, while Ficus (the Fig) was very common, and Casuarina (the Switch Plant) seems to have been widely spread. Magnolias also were common, and it appears that Platanus (the Plane) and Eucalyptus coexisted with them.

It will be immediately recognized that the above plants have all living representatives, either wild or cultivated, growing in this country at the present day, so that they are more or less familiar objects, and there appears to have been no striking difference between the early flowering plants and those of the present day. Between the ancient Lycopods, for example, and those now living the differences are very noteworthy; but the earliest of the known flowering plants seem to have been essentially like those now flourishing. It must be remembered in this connection that the existing flowering plants are immensely nearer in point of time to their origin than are the existing Lycopods, and that when such æons have passed as divide the present from the Palæozoic, the flowering plants of the future may have dwindled to a subordinate position corresponding to that held by the Lycopods now.

A noticeable character of the early flowering-plant flora, when taken as a whole, is the relatively large proportion of plants in it which belong to the family Amentiferæ (oaks, willows, poplars, &c.). This is supposed by some to indicate that the family is one of the most primitive stocks of the Angiosperms. This view, however, hardly bears very close scrutiny, because it derives its main support from the large numbers of the Amentiferæ as compared with other groups. Now, the Amentiferæ were (and are) largely woody resistant plants, whose very nature would render them more liable to be preserved as impressions than delicate trees or herbs, which would more readily decay and leave no trace. Similarly based on uncertain evidence is the surmise that the group of flowers classed as Gamopetalæ (flowers with petals joined up in a tube, like convolvulus) did not flourish in early times, but are the higher and later development of the flower type. Now, Viburnum (allied to the honeysuckle) belongs to this group, and it is found right down in the Cretaceous, and Sambucus (Elder, of the same family) is known in the early Tertiary. These two plants are woody shrubs or small trees, while many others of the family are herbs, and it is noteworthy that it is just these woody, resistant forms which are preserved as fossils; their presence demonstrates the antiquity of the group as a whole, and the absence of other members of it may be reasonably attributed to accidents of preservation. In the Tertiary also we get a member of the heath family, viz. Andromeda, and another tube-flower, Bignonia, as well as several more woody gamopetalous flowers.

Hence it is wise to be very cautious about drawing any important conclusions from the relative numbers of the different species, or the absence of any type of plant from the lists of those as yet known from the Cretaceous. When quantities of structurally preserved material can be examined containing the flowering plants in petrifactions, then it will be possible to speak with some security of the nature of the Mesozoic flora as a whole.

The positive evidence which is already accumulated, however, is of great value, and from it certain deductions may be safely made. Specimens of Cretaceous plants from various parts of the world seem to indicate that there was a very striking uniformity in the flora of that period all over the globe. In America and in Central Europe, for example, the same types of plants were growing. We shall see that, as time advanced, the various types became separated out, dying away in different places, until each great continent and division of land had a special set of plants of its own. At the commencement of the reign of flowering plants, however, they seem to have lived together in the way we are told the beasts first lived in the garden of Eden.

At the beginning of the Tertiary period there were still many tropical forms, such as Palms, Cycads, Nipa, various Artocarpaceæ, Lauraceæ, Araliaceæ, and others, growing side by side with such temperate forms as Quercus, Alnus, Betula, Populus, Viburnum, and others of the same kind. Before the middle of the Tertiary was reached the last Cycads died in what is now known as Europe; and soon after the middle Tertiary all the tropical types died out of this zone.