Halle has founded this species on specimens, from the Coal-Measures of Zwickau in Saxony, characterised by dimorphic lanceolate leaves in four rows, the larger being 4–6 mm. long: the smaller leaves have a ciliate edge. A comparison is made with the recent species Selaginella arabica Baker, S. revoluta Bak., and S. armata Bak. in which the leaves are described as ciliate. In the absence of sporangia and spores the species is placed in the genus Lycopodites.
Lycopodites lanceolatus (Brodie). Fig. 136.
- 1845 Naiadita lanceolata, Brodie[201].
Naiadea acuminata, Buckman[202]. - 1850 Naiadea lanceolata, Buckman[203].
Naiadea petiolata, Buckman[204]. - 1900 Naiadites acuminatus, Wickes[205].
- 1901 Naiadita lanceolata, Sollas[206] (figures showing habit of the plant).
- 1904 Lycopodites lanceolatus, Seward[207] (figure showing habit of the
plant).
Fig. 136. Lycopodites lanceolatus (Brodie). (After Miss Sollas. × 40.)
a, Sporangium wall; b, leaf.
c, remains of tubular elements in stem.
Specimens referred to this species were originally recorded by Brodie from Rhaetic rocks in the Severn valley, the name Naiadita being chosen as the result of Lindley’s comparison of the small and delicate leaves with those of recent species of the Monocotyledonous family Naiadaceae. The species may be described as follows:
Plant slender and moss-like in habit. The axis, which is delicate and thread-like, bears numerous linear acuminate or narrow ovate leaves reaching a length of approximately 5 mm. Under a low magnifying power the thin lamina of the leaves is seen to have a superficial layer of polygonal or rectangular cells arranged in parallel series ([fig. 136] b). There is no trace of midrib or stomata. The sporangia are more or less spherical and short-stalked, situated at the base of the foliage leaves and containing numerous tetrads of spores. The spores have a diameter of 0·08 mm.
Buckman founded additional species on differences in the shape of the leaves but, as Miss Sollas has pointed out, such differences as he noticed may be detected on the same axis. It was stated in an earlier chapter[208] that Starkie Gardner, on insufficient evidence, proposed to place Brodie’s plant among the Mosses. The discovery by Mr Wickes of new material at Pylle hill near Bristol afforded an opportunity for a re-examination of the species: this was successfully undertaken by Miss Sollas who was able to dissolve out spores from the matrix by dilute hydrochloric acid, and to recognise the remains of internal structure in the slender axes by exposing successive surfaces with the aid of a hone. It was found that sporangia occurred at the base of some of the leaves containing numerous tetrads of spores, the individual spores having a diameter of 0·08 mm., apparently twice as large as those of any recent species of Lycopodium. Fig. 136 shows a sporangium, a, at the base of a leaf, b. Indications of tubular elements were recognised in the stem and it is noteworthy that although the outlines of epidermal cells on the leaves are well preserved no stomata were found. The leaves of the recent American species Lycopodium alopecuroides Linn. var. aquaticum Spring[209], which lives under water, possess stomata. It is probable that in Lycopodites lanceolatus the leaves had a very thin lamina and may have been similar in structure to those of recent Mosses; the plant possibly lived in very humid situations or grew submerged. Miss Sollas’s investigations afford a satisfactory demonstration of the lycopodiaceous nature of this small Rhaetic species: as I have elsewhere suggested[210], the generic name Lycopodites should be substituted for that of Naiadita. Examples of this species may be seen in the British Museum.
The Rhaetic species from Scania, Lycopodites scanicus Nath.[211] (in litt.), recently re-described by Halle and originally referred by Nathorst to Gleichenia affords another example of the occurrence of a small herbaceous lycopod of Rhaetic age.
