Fossil plants, Vol. 1: [A text-book] for students of botany and geology

by A. C. Seward

STERNBERG AND BRONGNIART.

Sternberg endeavoured to apply to fossil plants the same methods of treatment as those made use of in the case of recent species. About the same time as Sternberg’s earlier parts were published, Adolphe Brongniart[17] of Paris began to enrich palaeobotanical science by those splendid researches which have won for him the title of the “Father of palaeobotany.” In Brongniart’s Prodrome, and Histoire des végétaux fossiles, and later in his Tableau des genres de végétaux fossiles, we have not merely careful descriptions and a systematic arrangement of the known species of fossil plants, but a masterly scientific treatise on palaeobotany in its various aspects, which has to a large extent formed the model for the best subsequent works on similar lines. From the same author, at a later date, there is at least one contribution to fossil plant literature which must receive a passing notice even in this short sketch. In 1839 he published an exhaustive account of the minute structure of one of the well-known Palaeozoic genera, Sigillaria; this is not only one of the best of the earliest monographs on the histology of fossil species, but it is one of the few existing accounts of the internal structure of this common type[18]. The fragment of a Sigillarian stem which formed the subject of Brongniart’s memoir is in the Natural History Museum in the Jardin des Plantes, Paris. It affords a striking example of the perfection of preservation as well as of the great beauty of the silicified specimens from Autun, in Central France. Brongniart was not only a remarkably gifted investigator, whose labours extend over a period connecting the older and more crude methods of descriptive treatment with the modern development of microscopic analysis, but he possessed the power of inspiring a younger generation with a determination to keep up the high standard of the palaeobotanical achievements of the French School. In some cases, indeed, his disciples have allowed a natural reverence for the Master to warp their scientific judgement, where our more complete knowledge has naturally led to the correction of some of Brongniart’s conclusions. Without attempting to follow the history of the science to more recent times, the names of Heer, Lesquereux, Zigno, Massalongo, Saporta and Ettingshausen should be included among those who rendered signal service to the science of fossil plants. The two Swiss writers, Heer[19] and Lesquereux[20], contributed numerous books and papers on palaeobotanical subjects, the former being especially well known in connection with the fossil floras of Switzerland and of Arctic lands, and the latter for his valuable writings on the fossil plants of his adopted country, North America. Zigno[21] and Massalongo[22] performed like services for Italy, and the Marquis of Saporta’s name will always hold an honourable and prominent position in the list of the pioneers of scientific palaeobotany; his work on the Tertiary and Mesozoic floras of France being specially noteworthy among the able investigations which we owe to his ability and enthusiasm[23]. In Baron Ettingshausen[24] we have another representative of those students of ancient vegetation who have done so much towards establishing the science of fossil plants on a philosophical basis.

As in other fields of Natural Science, so also in a marked degree in fossil botany, a new stimulus was given to scientific inquiry by the application of the microscope to palaeobotanical investigation. In 1828 Sprengel published a work entitled Commentatio de Psarolithis, ligni fossilis genere[25]; in which he dealt in some detail with the well-known silicified fern-stems of Palaeozoic age, from Saxony, basing his descriptions on the characteristics of anatomical structure revealed by microscopic examination.

THE INTERNAL STRUCTURE OF FOSSIL PLANTS.

In 1833 Henry Witham of Lartington brought out a work on The Internal Structure of Fossil Vegetables[26]; this book, following the much smaller and less important work by Sprengel, at once established palaeobotany on a firmer scientific basis, and formed the starting point for those more accurate methods of research, which have yielded such astonishing results in the hands of modern workers. In the introduction Witham writes, “My principal object in presenting this work to the public, is to impress upon geologists the advantage of attending more particularly to the intimate organization of fossil plants; and should I succeed in directing their efforts towards the elucidation of this obscure subject, I shall feel a degree of satisfaction which will amply repay my labour[27].”

On another page he writes as follows,—“From investigations made by the most active and experienced botanical geologists, we find reason to conclude that the first appearance of an extensive vegetation occurred in the Carboniferous series; and from a recent examination of the mountain-limestone groups and coal-fields of Scotland, and the north of England, we learn that these early vegetable productions, so far from being simple in their structure, as had been supposed, are as complicated as the phanerogamic plants of the present day. This discovery necessarily tends to destroy the once favourite idea, that, from the oldest to the most recent strata, there has been a progressive development of vegetable and animal forms, from the simplest to the most complex[28].” Since Witham’s day we have learnt much as to the morphology of Palaeozoic plants, and can well understand the opinions to which he thus gives expression.

It would be difficult to overrate the immense importance of this publication from the point of view of modern palaeobotany.

The art of making transparent sections of the tissues of fossil plants seems to have been first employed by Sanderson, a lapidary, and it was afterwards considerably improved by Nicol[29]. This most important advance in methods of examination gave a new impetus to the subject, but it is somewhat remarkable that the possibilities of the microscopical investigation of fossil plants have been but very imperfectly realised by botanical workers until quite recent years. As regards such a flora as that of the Coal-Measures, we can endorse the opinion expressed at the beginning of the century in reference to the study of recent mosses—“Ohne das Göttergeschenk des zusammengesetzten Mikroskops ist auf diesem Felde durchaus keine Ernte[30].” A useful summary of the history of the study of internal structure is given by Knowlton in a memoir published in 1889[31]. Not long after Witham’s book was issued there appeared a work of exceptional merit by Corda[32], in which numerous Palaeozoic plants are figured and fully described, mainly from the standpoint of internal structure. This author lays special stress on the importance of studying the microscopical structure of fossil plants.

ENGLISH PALAEOBOTANISTS.

Without pausing to enumerate the contributions of such well-known continental authors as Göppert, Cotta, Schimper, Stenzel, Schenk and a host of others, we may glance for a moment at the services rendered by English investigators to the study of palaeobotanical histology. Unfortunately we cannot always extend our examination of fossil plants beyond the characters of external form and surface markings; but in a few districts there are preserved remnants of ancient floras in which fragments of stems, roots, leaves and other structures have been petrified in such a manner as to retain with wonderful completeness the minute structure of their internal tissues. During the deposition of the coal seams in parts of Yorkshire and Lancashire the conditions of fossilisation were exceptionally favourable, and thus English investigators have been fortunately placed for conducting researches on the minute anatomy of the Coal-Measure plants. The late Mr Binney of Manchester did excellent service by his work on the internal structure of some of the trees of the Coal Period forests. In his introductory remarks to a monograph on the genus Calamites, after speaking of the desirability of describing our English specimens, he goes on to say, “When this is done, we are likely to possess a literature on our Carboniferous fossils worthy of the first coal-producing country[33].” The continuation and extension of Binney’s work in the hands of Carruthers, Williamson, and others, whose botanical qualifications enabled them to produce work of greater scientific value, has gone far towards the fulfilment of Binney’s prophecy.