| 1826. | Calamites cruciatus, Sternberg[819]. |
| 1828. | Calamites cruciatus, Brongniart[820]. |
| 1831. | Calamites alternans, Germar and Kaulfuss[821]. |
| 1837. | Calamites approximatus, Lindley and Hutton[822]. |
| 1877. | Calamodendrofloyos cruciatus, Grand’Eury[823]. |
| 1878. | Calamodendron cruciatum, Zeiller[824]. |
| 1884. | Calamites (Eucalamites) cruciatus ternarius, Weiss[825]. |
| 1884. | „ „ „ quaternarius, Weiss[825]. |
| 1884. | „ „ „ genarius, Weiss[825]. |
| 1884. | „ „ multiramis, Weiss[825]. |
| 1888. | Calamites (Calamodendron) cruciatus, Zeiller[826]. |
This species occurs in the Upper, Middle and Lower Coal-Measures[827]. The casts of the cruciatus type have been found associated with wood possessing the structural features of the sub-genus Calamodendron[828], but our knowledge of the structure of the stem, and of the fertile branches of C. cruciatus is very imperfect. A restoration of Calamites (Eucalamites) cruciatus is given by Stur[829] in his classic work on the Calamites, but he does not make quite clear the supposed connection with the stems and the fertile shoots of the Asterophyllites type[830] which he describes. Another member of the Eucalamites group, which is better known as regards its foliage-shoots, is Calamites ramosus, a species first described by Artis[831] in 1825. Stems of this species have been found in connection with the branches and leaves of the Annularia[6] type, bearing Calamostachys[832] cones. In all probability pith-casts included in the sub-genus Eucalamites belonged to stems with foliage-shoots and probably also with cones of more than one form.
NOMENCLATURE.
In the above account of a few common pith-casts it has been pointed out that there is occasionally satisfactory evidence for connecting certain casts with wood of a particular structure, and with sterile and fertile foliage-shoots of a definite type. It is, however, impossible in many cases to recognise with any certainty the leaf-bearing branches and strobili of the different casts of Calamites; it is equally impossible to determine what type of pith-cast or what type of foliage-shoots belongs to petrified stem-fragments in which it is possible to investigate the microscopical features. The scattered and piece-meal nature of the material on which our general knowledge of Calamitean plants is based, necessitates a system of nomenclature which is artificial and clumsy; but the apparent absurdity of attaching different names to fragments, which we believe to be portions of the same genus, is of convenience from the point of view of the geologist and the systematist. As our material increases it will be possible to further simplify the nomenclature for Calamarian plants, but it is unwise to allow our desire for a simpler terminology to lead us into proposals which are based rather on suppositions than on established fact. If it were possible to discriminate between pith-casts of stems having the different anatomical characters designated by the three sub-genera, Arthropitys, Arthrodendron and Calamodendron, the genus Calamites might be used in a much narrower and probably more natural sense than that which we have adopted. The tests made use of by some authors for separating pith-casts of Calamodendron and Arthropitys stems do not appear to be satisfactory; we want some term to apply to all Calamitean casts irrespective of the anatomical features of the stems, or of the precise nature of the foliage-branches. As used in the present chapter, Calamites stands for plants differing in certain features but possessing common structural characters, which must be defined in a broad sense so as to include types which may be worthy of generic rank, but which for convenience sake are included in a comprehensive generic name. The attempts to associate certain forms of foliage with Arthropitys on the one hand and with Calamodendron on the other, cannot be said to be entirely satisfactory; we still lack data for a trustworthy diagnosis of distinct Calamarian genera which shall include external characters as well as histological features. If we restricted the genus Calamites to stems with an Arthropitys structure and an Asterophyllitean foliage, we should be driven into unavoidable error. Within certain limits it is possible to distinguish generically or even specifically between petrified branches, and we already possess material enough for fairly complete diagnoses founded on internal structure; but it is not possible to make a parallel classification for pith-casts and foliage-shoots. For this reason, and especially bearing in mind the importance of naming isolated foliage-shoots and stem-casts for geological purposes, I believe it is better to admit the artificially wide application of the name Calamites, and to express more accurate knowledge, where possible, by the addition of a subgeneric term. In dealing with distinctions exhibited by Calamitean stems it may be advisable to make use of specific names, but we must keep before us the probability of the pith-cast and petrified stem-fragment of the same plant receiving different specific names. If the structural type is designated by a special sub-genus, this will tend to minimise the anomaly of using more than one binominal designation for what may be the same individual.
CALAMITES AND EQUISETUM.
The following summary may serve to bring together the different generic and subgeneric terms which have been used in the foregoing account of Calamites.
| Subgenera having reference to the method of branching as seen in casts
or impressions of the stem-surface or in pith-casts.
Calamitina, Eucalamites, Stylocalamites. | Subgenera founded on anatomical characters in stems and branches.
Arthropitys, Calamodendron, Arthrodendron (new sub-genus substituted for Calamopitys). | Genus proposed for roots of Calamites before their real nature was recognised. The name refers to anatomical characters. Astromyelon. |
| Genera of which some species, if not all, are the leaf-bearing branches
of Calamites.
Calamocladus (including Asterophyllites), Annularia. | Generic names applied to strobili belonging to Calamites.
Calamostachys, Palaeostachya, Macrostachya, etc. | Genus including impressions of Calamite roots. Pinnularia. |
IV. Conclusion.
A brief sketch of the main features of Calamites suffices to bring out the many points of agreement between the arborescent Calamite plants and the recent Equisetums. The slight variation in morphological character among the present-day Horse-tails, contrasts with the greater range as regards structural features among the types included in Calamites. The Horse-tails probably represent one of several lines of development which tend to converge in the Palaeozoic period; the Calamite itself would appear to mark the culminating point of a certain phylum of which we have one degenerate but closely allied descendant in the genus Equisetum. We shall, however, be in a better position to consider the general question of plant-evolution after we have made ourselves familiar with other types of Palaeozoic plants. Grand’Eury’s[833] striking descriptions of forests of Calamites in the Coal-Measures of central France, enable us to form some idea of the habit of growth of these plants with their stout branching rhizomes and erect aerial shoots.
By piecing together the evidence derived from different sources we may form some idea of the appearance of a living Calamite. A stout branching rhizome ascended obliquely or spread horizontally through sand or clay, with numerous whorls or tufts of roots penetrating into swampy soil. From the underground rhizome strong erect branches grew up as columnar stems to a height of fifty feet or more; in the lower and thicker portions the bark was fissured and somewhat rugged, but smoother nearer the summit. Looking up the stem we should see old and partially obliterated scars marking the position of a ring of lateral branches, and at a higher level tiers of branches given off at regular or gradually decreasing intervals, bearing on their upper portions graceful green branchlets with whorls of narrow linear leaves. On the younger parts of the main shoot rings of long and narrow leaves were borne at short intervals, several leaf-circles succeeding one another in the intervals between each radiating series of branches. On some of the leaf-bearing branchlets long and slender cones would be found here and there taking the place of the ordinary leafy twigs. Passing to the apical region of the stem the lateral branches given off at a less and less angle would appear more crowded, and at the actual tips there would be a crowded succession of leaf-segments forming a series of overlapping circles of narrow sheaths with thin slender teeth bending over the apex of the tree.