PROCEEDINGS OF THE YORKSHIRE GEOLOGICAL AND POLYTECHNIC SOCIETY. EDITED BY JAMES W. DAVIS, F.S.A., F. G.S., &c. 1891. ON THE PRESENT STATE OF OUR KNOWLEDGE OF THE YORKSHIRE CALAMITÆ. BY THOMAS HICK, B.A., B.SC., ASSISTANT LECTURER IN BOTANY, OWENS COLLEGE, MANCHESTER. In matters of science, as well as in those of commerce and industry, it is well periodically to take stock of our possessions, estimate our gains and our losses, and endeavour to discover how and in what directions our success in the future may be greater than it has been in the past. In attempting to do this for the fossil plants known as the Calamite, I am moved by the hope that a fresh impulse may be given to Yorkshire Palæophytology, and as a result of this, that the gaps which at present exist in our knowledge of these plants may be speedily filled up. It will be observed from the title of the paper that it is limited. to the Yorkshire Calamita; but a further limitation will be found in the fact that I deal chiefly with those specimens which have their structure preserved in a more or less perfect condition, and which enable us to learn something of their anatomy and histology. I have no desire to mimimise the value of the casts and impressions of Calamita which are so abundant in the Coal Measures, for on many points their evidence is of the highest possible value. But however much they may teach us as to the external form of Calamita and the mutual relations of their various organs, the minute structure and internal organisation on which most questions of affinity depend, can only be learnt from those petrifactions in which such structure has been preserved. As in the past so in the future, Calamite with structure will be the safest guides to their affinities and organisation, while for the construction of the phylogenetic tree of the vegetable kingdom their aid will be absolutely indispensable. As is usually done in dealing with recent plants, it will be well to consider the various members of the Calamita in their natural order, beginning with the roots and then passing on successively to the stems, leaves, and reproductive organs. ROOTS AND ROOTLETS. Of the roots and rootlets of the Calamite little appears to be known. From statements made by Binney it would seem that in the genus Calamites both roots and rootlets were present. Of the former he says, "the termination of the root of a Calamite is exactly of the same form as the terminal part of a Stigmaria, both being club-shaped"; and of the latter, that "they very much resemble the rootlets of Stigmaria, if they are not identical with them," and are "arranged in regular quincunical order." Adventitious roots were given off from the nodes of the aerial stem at the tapering basal part and from the figures given in the literature, they appear to have been slender, cylindrical, and sometimes branched structures, the branching being apparently dichotomous. According to Solms-Laubach† some species of Calamita had subterraneous rhizomes which likewise gave off roots from the nodes, often crowded together in tufts, and which when seen in impressions, had the form of long usually simple ribbon-like stripes. Looking at those statements critically, one can scarcely avoid the suspicion that the quincunical arrangement of the rootlets mentioned by Binney requires further investigation. There is no case known among existing plants where such an arrangement of * Observations on the Structure of Fossil Plants found in the Carboniferous Strata. I. Calamites and Calamodendron, 1868, Palæontographical Soc. + Fossil Botany. Eng. Ed., pp. 308, 309. rootlets on a root is known to occur. On Stigmaria the rootlets have such an arrangement, but by many authorities it is maintained that Stigmaria is not morphologically a root. It will be noted moreover that nothing is said of the structure of the organs called roots and rootlets, and so far as I can gather our knowledge on this point is a perfect blank. It is true that Renault* would have us believe that all the forms of Astromyelon are roots of Calamodendron and Arthropitys, Astromyelon dadoxylinum being the root of the former, and Astromyelon Augustodunense that of the latter. But in the Yorkshire forms of Astromyelon there is nothing characterestic of root structure, and we may therefore venture to reject this determination, as is done by Solms-Laubach, until it is supported by better evidence than it is at present. THE STEM. From the accounts given in the literature, ably summarised by Solms-Laubach,† it would seem, as already stated, that some species of Calamites possessed subterranean rhizomes which gave off two kinds of branches. The first of these remained beneath the ground, like the parent rhizome, to whose nodes they were attached by a broad base. The second were aerial shoots, which were inserted upon the rhizome like the preceding, but their bases were curved and narrowed into a conical form, and had a relatively large number of short internodes. It would seem, too, that these aerial shoots bore laternal branches, which were cylindrical and of the non-tapering kind. The aerial stems arising from the rhizome were frequently tufted, forming a group round a common centre, whence it has been concluded they were annual, like those of the gigantic Equisetums of the Trias. The laws of branching of the aerial shoots have been at least. partially worked out by Weiss, who includes the number and arrangement of the branches among the characteristics of the four groups into which he divides the Calamita. * Nouvelles recherches sur le genre Astromyelon. Memoires de la Soc. des Sciences Naturelles de Saône et Loire, 1885. + Fossil Botany. Eng. Ed., pp. 308, 309. Beiträge zur fossilen Flora III., Steinkohlen-Calamarien II. The axial structure of this fruit seems sufficient to bring it into close relation with Arthropitys, as is confidently done by Williamson, but the insertion of the sporangiophores is so different from that of Equisetum, with which Arthropitys agrees in so many respects, that we cannot but wish that further specimens were forthcoming. Up to the present time only a few specimens have been discovered from the Lancashire Coal Measures, and we can therefore scarcely determine whether or not they represent the normal state of things. As Arthropitys is a Yorkshire as well as a Lancashire type, it is surely not extravagant to think that if our Coal Measures were carefully and persistently searched, the search would be rewarded with additional examples of this most interesting spike. Our Yorkshire beds have, however, yielded numerous examples of the strobili, which are known under the name of Calamostachys, and which were dealt with at some length in a valuable paper contributed to the Proceedings of this Society by Mr. Cash in 1887.* In its general structure, and even in a large number of details, this spike approaches so closely to the sporiferous spike of Equisetum, that it might be said to be almost exactly similar to it. But to say this, would be to ignore the fact that its axis is not yet as fully known as it ought to be before such an assertion would be scientifically justified. In the paper referred to, the views of several authorities with respect to Calamostachys are carefully collated, and it is shown that they are widely at variance with one another. Prof. Williamson is quoted as being of opinion "that Calamostachys Binneyana has much closer affinities with Asterophyllites than with Calamites," and elsewhere the same authority has expressed his conviction that its true affinities are with the Lycopodiacea. This determination it may be mentioned was based, in the main, upon the structure of the axis of the fruit, which may be regarded as the critical feature where its affinities are concerned. Recently, however, Williamson has seen reason to modify these views and in the "General Proc. of the Yorks. Geol. and Polyt. Soc., 1887, p. 444. + Philosophical Transactions, 1881, p. 299. At the time this opinion was expressed, Williamson regarded Asterophyllites as Lycopodiaceous. Index" to his memoirs, has placed Calamostachys Binneyana, Schimp., among the Calamariew. At the same time he expresses a suspicion that under that name more than one species of fruit may be comprehended. From a careful study of a number of preparations of this type of Calamostachys I have come to the conclusion that by this change Williamson has come nearer the truth as to its affinities than in his previous memoirs. It must not be overlooked, however, that to place some of the forms of Calamostachys Binneyana, Schimp., in the large group of Calamariea is not the same thing as to affirm that they are the fruits of some species of Calamita. That they are such is an opinion held by Carruthers, Binney, Schimper, and other palæophytologists, but to the best of my belief no specimen has hitherto been published whose axial tissues afford the evidence. necessary to give this view a complete and irrefragable foundation. We are in this position then, that, as was pointed out by Carruthers long ago, Calamostachys Binneyana, Schimp., agrees in almost every detail with the sporiferous spike of Equisetum, and is, therefore, probably a fruit of some Calamitean plant. But the tissues of the axis which would clinch the argument for or against such a determination, are in all specimens hitherto described, so imperfectly preserved that their evidence is not decisive and cannot, therefore, be invoked on either side. I need scarcely say, that to a palæophytologist this is most tantalising, and if he is a Yorkshireman it is doubly so, for the remains of Calamostachys Binneyana, Schimp., are not infrequent in the Yorkshire Coal Measures, and the conviction lies near that if they were thoroughly overhauled, the missing link would be found and this important question settled once and for all. It is proverbially unsafe to prophesy unless you know, and I will avoid doing so. But I have an unusually strong suspicion that the axis of our Yorkshire specimens of Calamostachys Binneyana will yet prove to agree with the stem of some form of Calamite, and that in some cases at least, this "fruit" will turn out to be the spike of Arthropitys. Be this, however, as it may, the time appears to have * Proc. of the Manchester Lit. and Phil. Soc, 4th Ser., vol. iv. |