Fig. 100. Calamites (Calamitina) approximatus Brongn. Lower Coal-Measures of Ayrshire.
x, impression of the wood.
(From a specimen in the collection of Mr R. Kidston.)
We have so far noticed the connection of certain forms of pith-casts (e.g. Calamites approximatus), and Asterophyllitean shoots with stems of the sub-genus Calamitina.
As regards the strobili our knowledge is far from satisfactory. Stur[777] figures some fertile branches bearing long and narrow strobili, either Palaeostachya or Calamostachys, in close association with Calamitina stems, and Renault and Zeiller[778] give illustrations of the association of Calamitina stems with large strobili of the Macrostachya form.
Before Weiss proposed the term Calamitina, various authors had figured this form of Calamite under a distinct generic name (e.g. Hippurites of Lindley and Hutton[779], Cyclocladia[780], Macrostachya[781], &c.). Stems of this type have also been described by more recent writers under different names, and considerable confusion has been caused by the use of numerous generic designations for forms of Calamitina. Some small fragments of Calamitina stems were described by Salter[782] in 1863 as portions of a new species of the Crustacean Eurypterus (E. mammatus). In 1869 Grand’Eury proposed the generic name Calamophyllites[783] for stems bearing verticils of Asterophyllites shoots; his description of such stems agrees with Weiss’ Calamitina, but as Grand’Eury’s name is used in a narrower sense as implying a connection with Asterophyllites, it is more convenient to adopt Weiss’ term in spite of the priority of Calamophyllites. In the Fossil flora of Commentry we find some flattened stems of the Calamitina type described under different generic names, as Arthropitys approximatus[784] and as Macrostachya[785].
The determination of distinct species of the sub-genus Calamitina is rendered almost hopeless by the variation in the different branches of the same individual, and by the difficulty of connecting surface-impressions with casts of the pith-cavity.
A typical example of the Calamitina type of Calamites was figured by Sternberg[786] in 1821 as Calamites varians. This has been adopted by Weiss[787] as a comprehensive species including several different ‘forms’ of stems, which differ from Sternberg’s fossil in such points as the number of nodes between the branch-whorls and the number of branches in each whorl. The result of this system of nomenclature is the separation of portions of one specific type under different form-names. It must be clearly recognised that accurate specific diagnoses are practically impossible when we have to deal with fragments of plants, some of which are mere pith-casts, while others show the surface features. The specimen represented in fig. 99 agrees with a stem described by Ettingshausen[788] in 1855 as Calamites Göpperti, and as a matter of convenience a member of the Calamitina group showing such characters may be referred to as Calamites (Calamitina) Göpperti (Ett.). The following list, which includes a few synonyms of this form, may suffice to illustrate the difficulties connected with accurate systematic determinations.
Calamites (Calamitina) Göpperti (Ett.). Fig. 99.
| 1855. | Calamites Göpperti, Ettingshausen[789]. |
| 1869. | Calamites (Calamophyllites) Göpperti, Grand’Eury[790]. |
| 1874. | Cyclocladia major, Feistmantel[791]. |
| 1874. | Calamites verticillatus, Williamson[792]. |
| 1876. | Calamitina Göpperti, Weiss[793]. |
| 1884. | Calamites (Calamitina) varians abbreviatus, Weiss[794]. |
| 1884. | Calamites (Calamitina) varians inconstans, Weiss[795]. |
| 1887. | Calamites Sachsei, Stur[796]. |
| 1888. | Calamophyllites Göpperti, Zeiller[797]. |
This species is characterised by the smooth bark, which may be traversed by a few irregular longitudinal fissures; most of the nodes bear a series of small leaf-scars, and at fairly regular intervals a node is immediately succeeded by a circle of contiguous branch-scars, 8–12 in a whorl. The pith-cast of this type of stem has short ribbed internodes separated by rather deep nodal constrictions; the branch-whorls being represented by a series of pits on the nodal constrictions recurring at corresponding intervals to the whorls of branch-scars on the surface of the stem. Leaves narrow and linear in form, like those on Asterophyllitean branches, are occasionally associated with this type of stem.