Selaginellites primaevus (Gold.). [Fig. 135], A, [fig. 138].
- 1855 Lycopodites primaevus, Goldenberg[227].
- 1870 Lycopodium primaevum, Schimper[228].
- 1907 Selaginellites primaevus, Halle[229].
Fig. 138. Selaginellites primaevus (Gold.). (After Goldenberg.)
In habit this species, first recorded by Goldenberg from the Coal-Measures of Saarbrücken, is similar to S. Suissei Zeill.
The drawing reproduced in [fig. 138] is a copy of that of the type-specimen: another specimen, named by Goldenberg, is figured by Halle in his recently published paper. The leaves appear to be distichous: no smaller leaves have been detected, though Halle is inclined to regard the plant as heterophyllous. The sporophylls, borne in slender terminal strobili, are smaller than the foliage leaves and spirally disposed ([fig. 138]; smaller specimen). Halle succeeded in demonstrating that some of the sporangia contained a single tetrad of spores, each spore having a diameter of 0·4–0·5 mm. No microspores were found, but it is clear that the species was heterosporous and that it agrees with recent species in having only four spores in the megasporangium.
Selaginellites elongatus (Gold.). [Fig. 135], B, D.
The shoots of this species resemble the recent Lycopodium complanatum; they differ from those of Selaginellites primaevus in their long and narrow branches which bear two forms of leaf. The longer leaves, arranged in opposite pairs, are slightly falcate; the smaller leaves are appressed to the axis and have a triangular cordate lamina. Another peculiarity of this species is the occurrence of sporangia in the axil of the foliage leaves, a feature characteristic of the recent Lycopodium Selago. In recent species of Selaginella the sporophylls are always in strobili. No microspores have been found nor the walls of megasporangia, but tetrads of megaspores were isolated by Halle: the spores have three radiating ridges ([fig. 135], B) connected by an equatorial ridge. Halle estimates the number of spores (0·45 mm. in diameter) in a sporangium at 20 to 30. In size as in number the spores exceed those of recent species and agree more nearly with the megaspores of S. Suissei.
It would seem to be a general rule that the spores (megaspores) of the fossil herbaceous species exceeded considerably in dimensions those of recent forms and on the other hand were smaller than those of the Palaeozoic arborescent species.