March 27, 1879. THE PRESIDENT in the Chair. The Presents received were laid on the table, and thanks ordered for them. The following Papers were read :— I. "On the Organization of the Fossil Plants of the Coal Measures. Part X." By W. C. WILLIAMSON, F.R.S., Professor of Natural History in Owens College, Manchester. Received March 5, 1879. (Abstract.) The still existing differences of opinion respecting the botanical affinities of the Sigillariæ give value to every new fact calculated to throw light upon the question. In 1865, Edward Wunsch, Esq., of Glasgow, made a discovery, which proves to have an important bearing upon it. He found, at Laggan Bay, in Arran, a series of rather thin Carboniferous strata, separated by thick beds of volcanic ash, and in one of the Carboniferous shales especially, he discovered the bases of the stems of numerous very large trees, standing perpendicularly to the shales. These trees have been referred to by several authors as Sigillarian. In the summer of 1877, Mr. Wunsch and I employed quarrymen to make extensive excavations amongst these strata, for the purpose of adding to the extensive series of specimens which he had obtained, and the whole of which he kindly placed in my hands. The aggregate result of these explorations was to show that the conclusion previously arrived at, viz., that the stems had belonged to a grove of Sigillarian trees was unsupported by a solitary fact. These stems were of very large size, showing that they had belonged to fully grown trees. None of them displayed any traces of leaf-scars, having outgrown the stages at which such scars would remain visible. Their outer surfaces were scored with deep irregular longitudinal fissures, resulting from internal growth and consequent expansion, and which appear to have been mistaken for the longitudinal grooves and ridges of a Sigillarian bark. Such, however, they certainly were not, since, in every instance, the surface bark had been entirely thrown off, and the fissures entered deeply into the subjacent bark layer. In most of the stems, this comparatively thin bark layer was the only one that remained, the greater portion of the inner bark and the central vascular axis having disappeared, leaving a large cylindrical cavity, which was filled up with volcanic ash. These stems failed to display a single feature, justifying the conclusion that they were Sigillarian. In two of them the central cavity, instead of being filled with ash, was filled with miscellaneous heaps of vegetable matter, amongst which were large fragments of the vascular axes of various plants, such as Lepidodendra and Stigmariæ, but in one of the largest stems were five or six decorticated vascular cylinders of Diploxyloid stems, of the largest size, and which, though arranged parallel to the long axis of the cylinder which enclosed them, obviously did not belong to them, but had been floated in from without. The supposition that these had been young stems that had grown within the hollow protecting cylinders, from spores, accidentally introduced, is wholly untenable, since each one of these several vascular axes has been the centre of a stem fully as large as that within which we found them aggregated. Of course, these Diploxyloid vascular axes had the organization which Brongniart and the younger school of French botanists which still upholds his views on this point, believe to be characteristic of true Sigillariæ-a conclusion from which I have long dissented. The only fragment we found, that threw any light upon the character of the leaf-scars that had indented the surfaces of these fully grown stems, was a well-defined example of the Lepidodendroid type. We directed careful attention to the nature of the smaller fragments of branches and foliage which abounded in the volcanic ash with which the large stems were overlaid. These consisted of Lepidodendroid branches and twigs of all sizes and ages, and no doubt was left upon my mind that they were really the disjecta membra of the stems around which they were so profusely scattered. The only fruits that have been obtained from the same locality are Lepidostrobi, most of which contain macrospores and microspores. Unless we are prepared to believe that this Arran deposit contained, on the one hand, numerous stems without branches, and, on the other, yet more numerous branches without stems, we must recognise in these specimens the complementary elements of a grove of Lepidodendroid trees. One specimen found is a very important one. It has a mean diameter of six inches, and is either a small stem or a very large branch. Internally it exhibits the same structure as all the smaller Lepidodendroid branches, except so far as it is modified by size and age. But in addition to its other features, it exhibits a very narrow exogenous ring surrounding the ordinary Lepidodendroid one, thus giving some clue to the size attained by such branches before the internal organization passed from the Lepidodendroid to the Sigillarian type. I have at last succeeded in obtaining the Strobilus, to which the remarkable macrospores and microspores figured in my last memoir belong. It unexpectedly proves to be a very small one, being little more than an inch in length. Further specimens have shown that the abnormal peduncles of the macrospores shown in Plate 23, fig. 64, are wholly due to the partial collapse of the spore-wall. Further specimens have also been obtained of the Strobilus and its spores represented in Plate 22, figs. 38-57. These examples possess the central vascular axis in a perfect state, which portion was lacking in the previously known examples. It proves to have an individuality as distinctive as that of the spores and sporangia which it bore. The important discovery by Mr. D'Arcy Thompson, of Edinburgh, of young branches of Ulodendron with reproductive cones actually attached to the scars characteristic of the genus, finally settles the nature and functions of these scars, showing that they mark the positions from which bilaterally arranged deciduous organs of fructification have fallen. The structure of Calamostachys Binneyana has had further light thrown upon it, sustaining my previously expressed convictions that it had a triquetrous axis, and that consequently its affinities were with Asterophyllites and Sphenophyllum, and not with Calamites. A specimen demonstrates that the six vascular bundles going to the six fertile sporangiophores were given off in pairs from the three truncated angles of a triangular vascular axis-an orientation absolutely identical with that represented in similar sections of stems of Sphenophyllum, published by M. Renault. The recent discovery by Herr Stur, of Vienna, of a plant in which Sphenophylloid and Asterophyllitean leaves are found upon a common stem, establishes the correctness of my previous conclusions as to the very close affinities of these two genera. Two new fern petioles or stems have been obtained from Halifax, to which I have given the name of Rachiopteris robusta and R. insignis. In one specimen of the latter, the large vessels of the central bundle are full of Tylose cells, whilst a second example exhibits no trace of them. This shows the existence or non-existence of Tylose to be a characteristic having no specific value. Since my last memoir was written I have obtained several new forms of cryptogamic conceptacles-similar to those previously described under the generic name of Sporocarpon-as well as been able to throw additional light upon some of those previously described. No clue has yet been obtained as to the plants to which these very remarkable organisms belonged. A large series of specimens from Oldham and Halifax has enabled me to investigate in detail the very curious objects to which Mr. Carruthers gave the name of Traquairia, and which that observer believes to be a form of Radiolarian life. Their very elaborate organization can scarcely be made intelligible without the aid of plates. In a 448 Organization of Fossil Plants of the Coal Measures. [Mar. 27, previous memoir (" Phil. Trans." 1874, p. 56), I ventured to doubt the correctness of Mr. Carruthers' conclusions, and expressed my conviction that these objects resembled spores rather than protozoan skeletons. Further study of their details of structure has only strengthened this opinion which has also received the important support of Professors Hæckel and Strasburger, of Jena, both of whom have carefully studied my collection of specimens. These objects are small spheres-the sphere-wall of which is prolonged into a series of long radiating tubes not unlike the muricated spines of a Cidaris. In their young state each murication gives off a delicate thread or threads, which ramified freely in an apparently mucilaginous or gelatinous, structureless, investing magma. In older specimens these threads developed into branching and radiating cylindrical tubes which, like the primary ones, had very thin walls. Within the outer sphere-wall, which consists of the coalesced bases of these branching tubes, were at least two other thin layers of membrane, and in several of the specimens the interior of the capsule is filled with cells, exactly like those seen in the corresponding cavities of Lycopodiaceous macrospores found in the Halifax deposits from which the finest Traquairia have been obtained. These objects differ considerably from all known reproductive structures; but I agree with Professor Hæckel in his very decided rejection of them from the Radiolarian group of organisms, and with his conclusion that they are vegetable and not animal structures. Professor Strasburger thinks it most probable that their affinities are with the macrospores of the Rhizocarpa. In my previous memoir I gave three very small figures of some minute objects, which exactly resemble, in their minutest details, the zygospores of some of the Desmidiaceae. Many additional examples of these objects have been discovered, enabling me to throw further light upon them. Their resemblance to these zygospores has been made increasingly obvious, but I dare not venture to assign to them a Desmidiaceous origin, since the most extended research, and the resulting discovery of large numbers of these organisms, have yet failed. to bring to light the faintest trace of a true Desmid. Under these circumstances I have assigned to several species of these organisms the generic name of Zygosporites. The seed described in my last memoir but one, under the name of Lagenostoma ovoides, always exhibited a thick carbonised testa, in which no structure could be observed. I have now discovered that the thick outer layer consisted of very hard cubical or slightly oblong schlerenchymatous cells, whilst a thin and delicate inner membrane was composed of small spiral prosenchymatous ones. An additional specimen of the woody axis of Dadoxylon exhibits the paired divergent structures passing outwards to the back in the shape of two large, radial prolongations of the cellular pith; and which must obviously have gone off the branches-either to ordinary ones or to pairs of fruit-spikes. Myriads of the vegetable fragments both from Oldham and Halifax are drilled in all directions with rounded insect or worm borings, and further traces of these xylophagous animals are seen in innumerable clusters of small Coprolites of various sizes; the size of those composing each cluster being uniform. Desirous of verifying Count Castracane's alleged discovery of Diatoms in coal, specimens of twenty-two examples of coal from various localities in Yorkshire, Lancashire, and Australia were reduced, after the Count's method, to a small residue of ash. This work was done for me in the chemical laboratory of Owens College through the kindness of Professor Roscoe. Like Mr. F. Kitton, of Norwich, the Rev. E. O'Meara, of Dublin, and the Rev. G. Davidson, of Logie Coldstone, I have failed to discover the slightest trace of these organisms in coal. The last objects described are some minute organisms from the Carboniferous limestones of Rhydmwyn, in Flintshire, and which were supposed by Professor Judd to have been siliceous Radiolarians from which the silica had disappeared and been replaced by carbonate of lime. I fail to find any confirmation of this conclusion. The objects appear to me to constitute an altogether new group of calcareous spherical organisms that may either have been allied to the Foramnifera, or have had some affinities with the Rhabdoliths and Coccoliths. I have proposed for several species of the organisms the generic name of Calcisphæra. Myriads of objects of similar character, but of larger size, constitute the greater portion of a. Coruiferous limestone from the Devonian beds of Kelly's Island, U.S.A. II. "Observations on the Physiology and Histology of Convoluta Schultzi." By P. GEDDES. Communicated by J. BURDON SANDERSON, M.D., F.R.S., Professor of Physiology in University College, London. Received March 10, 1879. PART I.-Physiology. Chlorophylloid green colouring matters are known to exist in the tissues of a not inconsiderable number of animals belonging to very various invertebrate groups-Protozoa, Porifera, Coelenterata, Vermes, and even Crustacea;* but all information as to the function of chlorophyll in the animal organism is wanting. Wöhler, it is true, found many years ago that Chlamydomonas, Euglena, &c., evolve oxygen in sunlight, and Schmidt prepared from Euglena viridis a body isomeric See list in Sach's "Botany," Eng. ed., p. 687, note. |