Fig. 137. Lycopodites falcatus L. and H. From the Inferior Oolite of Yorkshire. (Nat. size. M.S.)

Lycopodites falcatus Lind. and Hutt. Fig. 137.

In 1822 Young and Bird[215] figured a specimen from the Inferior Oolite rocks of the Yorkshire coast bearing “small round crowded leaves,” which was afterwards described by Lindley from additional material obtained from Cloughton near Scarborough as Lycopodites falcatus. The example represented in [fig. 137] shows the dichotomously branched shoots bearing two rows of broadly falcate leaves. A careful examination of the type-specimen[216] revealed traces of what appeared to be smaller leaves, but there is no satisfactory proof of heterophylly. No sporangia or spores have been found. This British species has been recorded from Lower Jurassic or Rhaetic rocks of Bornholm[217] and a similar though probably not identical type, Lycopodites Victoriae[218], has been recognised in Jurassic strata of Australia (South Gippsland, Victoria). An Indian plant described by Oldham and Morris[219] from the Jurassic flora of the Rajmahal hills as Araucarites (?) gracilis and subsequently transferred by Feistmantel to Schimper’s genus Cheirolepis[220] may be identical with the Yorkshire species. The Jurassic fragments described by Heer from Siberia as Lycopodites tenerrimus[221] may be lycopodiaceous, but they are of no botanical interest.

Other examples of Mesozoic Lycopods have been recorded, but in the absence of well-preserved shoots and sporangia they are noteworthy only as pointing to a wide distribution of Lycopodites in Jurassic and Cretaceous floras[222].

From Tertiary strata species of supposed herbaceous lycopods have been figured by several authors, one of the best of which is Selaginella Berthoudi Lesq.[223] from Tertiary beds in Colorado. This species agrees very closely in the two forms of leaf with Selaginella grandis, but as the specimens are sterile we have not sufficient justification for the employment of the generic name Selaginellites.

Selaginellites.

This generic name has been instituted by Zeiller[224] for specimens from the coal basis of Blanzy (France). It is applied to heterosporous species with the habit of Selaginella: Zeiller preferred the designation Selaginellites to Selaginella on the ground that the type species differs from recent forms in having more than four megaspores in each megasporangium. It is, however, convenient to extend the term to all heterosporous fossil species irrespective of the spore-output.

Selaginellites Suissei Zeiller.

This species was described in Zeiller’s preliminary note[225] as Lycopodites Suissei, but he afterwards transferred it to the genus Selaginellites. In habit the plant bears a close resemblance to Lycopodites macrophyllus of Goldenberg; the shoots, 1–3 mm. thick, are branched in a more or less dichotomous fashion and bear tetrastichous leaves. The larger leaves reach a length of 4–6 mm. and a breadth of 2–3 mm.; the smaller leaves are described as almost invisible, closely applied to the axis, oval-lanceolate and 1–2 mm. long with a breadth of 0·5–0·75 mm. Long and narrow strobili (15 cm. by 8–10 mm.) terminate the fertile branches; these bear crowded sporophylls with a triangular lamina and finely denticulate margin. Oval sporangia were found on the lower sporophylls containing 16–24 spherical megaspores 0·6–0·65 mm. in diameter. The outer membrane of the spore is characterised by fine anastomosing ridges and thin plates radiating from the apex and forming an equatorial collarette. The microspores have a diameter of 40–60μ and the same type of outer membrane as in the megaspores. The megaspores of the recent species Selaginella caulescens, as figured by Bennie and Kidston[226], resemble those of the Palaeozoic type in the presence of an equatorial flange. It is interesting to find that, in spite of the occurrence of 16–24 megaspores in a single sporangium the size of the fossil spores exceeds that of the recent species.