(CALAMARIEAE.)
In order to minimise repetition and digression the following account of the Calamarieae is divided into sections, under each of which a certain part of the subject is more particularly dealt with. After a brief sketch of the history of our knowledge of Calamites, and a short description of the characteristics of the genus, the morphological features are more fully considered. A description of the most striking features of the better known Calamitean types is followed by a short discussion on the question of nomenclature and classification, and reference is made to the manner of occurrence of Calamites and to some of the possible sources of error in identification.
D. Calamites.
I. Historical Sketch.
In the following account of the Calamarieae the generic name Calamites is used in a somewhat comprehensive sense. As previous writers have pointed out, it is probable that under this generic name there may be included more than one type of plant worthy of generic designation. Owing to the various opinions which have been held by different authors, as to the relationship and botanical position of plants now generally included in the Calamarieae, there has been no little confusion in nomenclature. Facts as to the nature of the genus Calamites have occasionally to be selected from writings containing many speculative and erroneous views, but the data at our disposal enable us to give a fairly complete account of the morphology of this Palaeozoic plant.
In the earliest works on fossil plants we find several figures of Calamites, which are in most cases described as those of fossil reeds or grasses. The Herbarium diluvianum of Scheuchzer[580] contains a figure of a Calamitean cast which is described as probably a reed. Another specimen is figured by Volkmann[581] in his Silesia subterranea and compared with a piece of sugar-cane. A similar flattened cast in the old Woodwardian collection at Cambridge is described by Woodward[582] as “part of a broad long flat leaf, appearing to be of some Iris, or rather an Aloe, but ’tis striated without.” Schulze[583], one of the earlier German writers, figured a Calamitean branch bearing verticils of leaves, and described the fossil as probably the impression of an Equisetaceous plant. It has been pointed out by another German writer that the Equisetaceous character of Calamites was recognised by laymen many years before specialists shared this view.
One of the most interesting and important of all the older records of Calamites is that published by Suckow[584] in 1784. Suckow is usually quoted as the author of the generic name Calamites; he does not attempt any diagnosis of the plant, but merely speaks of the specimens he is describing as “Calamiten.” The examples figured in this classic paper are characteristic casts from the Coal-Measures of Western Germany. Suckow describes them as ribbed stems, which were found in an oblique position in the strata and termed by the workmen Jupiter’s nails (“Nägel”). Previous writers had regarded the fossils as casts of reeds, but Suckow correctly points out that the ribbed character is hardly consistent with the view that the casts are those of reeds or grasses. He goes on to say that the material filling up the hollow pith of a reed would not have impressed upon it a number of ribs and grooves such as occur on the Calamites. He considers it more probable that the casts are those of some well-developed tree, probably a foreign plant. Equisetum giganteum L. is mentioned as a species with which Calamites may be compared, although the stem of the Palaeozoic genus was much larger than that of the recent Horse-tail. The tree of which the Calamites are the casts must, he adds, have possessed a ribbed stem, and the bark must also have been marked by vertical ribs and grooves on its inner face. It is clear, therefore, that Suckow inclined to the view that Calamites should be regarded as an internal cast of a woody plant. Such an interpretation of the fossils was generally accepted by palaeobotanists only a comparatively few years ago, and the first suggestion of this view is usually attributed to Germar, Dawes, and other authors who wrote more than fifty years later than Suckow.
One of the earliest notices of Calamites in the present century is by Steinhauer[585], who published a memoir in the Transactions of the American Philosophical Society in 1818 on Fossil reliquia of unknown vegetables in the Carboniferous rocks. He gives some good figures of Calamitean casts under the generic name of Phytolithus, one of those general terms often used by the older writers on fossils. Among English authors, Martin[586] may be mentioned as figuring casts of Calamites, which he describes as probably grass stems. By far the best of the earlier figures are those by Artis[587] in his Antediluvian Phytology. This writer does not discuss the botanical nature of the specimens beyond a brief reference to the views of earlier authors. Adolphe Brongniart[588], writing in 1822, expresses the opinion that the Calamites are related to the genus Equisetum, and refers to M. de Candolle as having first suggested this view. In a later work Brongniart[589] includes species of Calamites as figured by Suckow, Schlotheim, Sternberg and Artis in the family Equisetaceae. Lindley and Hutton[590] give several figures of Calamites in their Fossil flora, but do not commit themselves to an Equisetaceous affinity.
An important advance was made in 1835 by Cotta[591], a German writer, who gave a short account of the internal structure of some Calamite stems, which he referred to a new genus Calamitea. The British Museum collection includes some silicified fragments of the stems figured and described by Cotta in his Dendrolithen. Some of the specimens described by this author as examples of Calamitea have since been recognised as members of another family.
PETZHOLDT AND UNGER.