EDITED BY JAMES W. DAVIS, F.S.A., F.G.S., &c.

1893.

CALAMOSTACHYS BINNEYANA, SCHIMP. BY THOMAS HICK, B.A., B.SC., ASSISTANT LECTURER IN BOTANY, OWENS COLLEGE, MANCHESTER.

Our knowledge of the structure and characteristics of the sporiferous spike or strobilus now known as Calamostachys Binneyana is almost entirely based upon the descriptions and figures published by Carruthers, Binney,† and Williamson.‡ By Carruthers it was named Volkmannia Binneyi, by Binney Calamodendron commune, and by Schimper Calamostachys Binneyana, a name which has been generally adopted by later writers.

The specimens described by these authors being in no case perfect, it is not surprising that on some important points our knowledge of the fossil is anything but complete, while it is well-known that as regards its affinities Carruthers and Williamson came to widely different conclusions.

Under these circumstances I propose to review its structure and affinities in the light of a series of preparations lately placed in my hands by W. Cash, Esq., of Halifax. They consist of a number

* Journal of Botany. December, 1867.

+ Observations on the Structure of Fossil Plants found in Carboniferous Strata, Part I., Calamites and Calamodendron. Palæontographical Society, 1868.

On the Organisation of the Fossil Plants of the Coal Measures. Philosophical Transactions, 1871-1891,

of sections cut by Mr. James Binus, of the same town, in which the structure of the spike is so well preserved as to give much additional information on important points of detail, clear up others that have hitherto been doubtful, and at the same time throw considerable light on the question of affinities.

The general structure of Calamostachys Binneyana, as hitherto described, may be summarised as follows:

The axis of the spike consists of a series of nodes and internodes, the former of which bear alternately whorls of sterile bracts and sporangiophores. The nodes bearing bracts are extended outwards to form what Williamson has termed the "nodal disks." From the margin of each disk, the bracts, usually twelve in number, are given off, and these turning upwards ascend beyond the bases of the members of the next higher whorl, with which they alternate. The sporangiophores are placed about midway between the "nodal disks," and stand at right angles to the axis. Their distal ends are dilated into peltate heads to the inner surface of which the sporangia are attached, of which each carries four. Hence, as has often been pointed out, the spike bears a strong resemblance to that of Equisetum, the chief difference being the intercalation of a "nodal disk" with its sterile bracts between the successive whorls of sporangiophores.

As regards the histology of the strobilus the authorities referred to were not in a position to obtain final and decisive results, and hence perhaps their divergent views. In dealing with it, it will conduce to clearness if we first epitomise the statements already published, and then present the results obtained by a study of the fresh material.

THE AXIS OF THE STROBILUS.

Carruthers in the paper already referred to writes of the axis as follows:-"The axis of the strobilus has a bundle of fine scalariform tissue in its center, forming about a third of its diameter, and generally appearing free from the surrounding cellular tissue which is composed of somewhat elongated cells."*

On the accompanying plate he gives a figure (fig. 3) which is referred to as illustrating this structure, but the section it represents is an oblique one, and the figure is not conclusive as to the central position of the vascular tissue.

Binney in his account of the axis is somewhat lacking in precision. Without quoting his exact words it will suffice to say that from his description and figures there can be little doubt that he regarded the central part of the axis as being composed of vascular tissue of the scalariform type. His figures which were admirably drawn by Fitch, represent two transverse and four longitudinal sections. In the former, the elements in the center of the axis remind us much more of parenchyma than of vascular tissue, while the latter not being exactly radial, are certainly not decisive of the vascular nature of the central part of the axis.

Williamson has dealt with the minute structure of the axis in several of his memoirs on carboniferous plants. In Part I.,† without entering into details, he insists that the axis differs widely from the stem of Calamites, stating that "the vascular tissues are all found in the central part." In Part V., the strobilus is subjected to a detailed description, as a result of which the center of the axis is said to be "composed of a cluster of barred vessels," and an enlarged figure of part of a transverse section of the axis is given to illustrate this feature. In Parts IX. || and X. § the same view is maintained, and in the latter we have additional figures, both longitudinal and transverse, in the former of which the central tissue is drawn as consisting of elongated vascular elements with scalariform markings. In Part XV. however a change is made in the mode of description, and the central part of the axis is spoken of as containing a "quasi-medullary cellular parenchyma." Finally, in the first part of an index to the Memoirs, a foot-note is inserted stating that "there has been much difficulty in defining the structure of this axis which varies much in different specimens." At the same time it is added that the center

* Loc. cit., pp. 23-27.

Op. cit., Pt. v., 1874, p. 61.

§ Ibid., Pt. x., 1880, p. 503.

Op. cit., Part I., 1871, p 501.

|| Ibid., Pt. ix., 1878, p. 334. Ibid., Pt. xv., 1889, p. 160.

** Proceedings of the Manchester Literary and Philosophical Society, 1890-91.

Reprint, p. 14.

of the specimen described in Part V. is "probably cellular, not vascular, as described in the Memoir." Other undescribed specimens are also referred to as showing a central medulla" which is distinctly cellular.”

As regards the vascular bundles which in some cases surround the center of the axis, nothing is said by Carruthers and Binney, and our present knowledge of them is entirely due to Williamson. Unfortunately, however, Williamson's description of them was dominated by the idea that they enclosed a strand of vascular tissue, and this led him to compare them with the secondary vascular bundles of the plant he then termed Asterophyllites

From all this it is clear that much confusion exists respecting the histological composition of the axis of Calamostachys Binneyana, and until it is cleared up no serious attempt can be made to remove the equally prevailing confusion which obscures its affinities and systematic position.

Turning now to the new material, it may be well to state at the outset that after a careful and prolonged study of it, I have come to the conclusion that Calamostachys Binneyana is not only characterised by a parenchymatous pith in the center of the axis, but also by a ring of primary vascular bundles round that pith, which have the characteristics of those of Cubimites.

Among the transverse sections are several which have been well preserved, and are more than usually perfect so far as concerns the axis at least. In these the parenchymatous character of the central tissue is indicated not only by the appearance and arrangement of the elements, their irregularities of size and shape, and the presence of intercellular spaces, but also by the fact that neither the side walls where inclined to the vertical, nor the transverse walls where visible, show any traces of scalariform or other vascular markings. For demonstrative evidence, however, we must go to the longitudinal sections, one of which is represented in figs. 2, Pl. I., and 3, Pl. II. This is a magnificent specimen whose axis is practically perfect, and both in this and other respects seems much superior to those previously published. Both extremities appear to be wanting, but the part pre

* Now known to be Sphenophyllum.