Fig. 318. Etapteris Scotti, P. Bert. (From Tansley, after Renault.)
Etapteris Scotti. Figs. [308], B; [309], E; [318].
P. Bertrand has proposed this name for a species of petiole from the Lower Coal-Measures of England referred by Binney[1177] to Zygopteris Lacattii Ren., and included by Williamson[1178] in his comprehensive genus Rachiopteris. Bertrand[1179] regards the English species, which is recorded also from Germany[1180], as distinct from Renault’s type[1181] and therefore proposes a new name. The petiole stele has the H-form, but its structure is simpler than that of the Ankyropteris petiole.
The horizontal band of xylem has at each end two oval groups of tracheae connected with it by a single row of xylem elements ([fig. 318]). From the lower part of each oval group a small strand is detached; the two strands from one side of the stele coalesce and then separate to pass into two pinnae. Fig. 308, B, shows four stages in the giving-off of the secondary branches. This species, therefore, produces four rows of branches in alternate pairs from the right and left sides of the petiole.
The first stage is shown at 0, 0, [fig. 308], B; the two projecting groups of protoxylem mark the points of departure of a pair of small strands. At 1, the projections are more prominent, and at 2 a pair of strands has become detached: at a later stage, 3, these two strands unite to divide later (4) into two slightly curved bundles.
Fig. 319.
- A–C. Sporangia of Etapteris (?).
- D–G. Botryopteris forensis. (After Renault.)
Our knowledge of the fructification of Etapteris is based on Renault’s account of sporangia, which he regarded as belonging to Zygopteris (Etapteris) Lacattii. They have the form of elongated slightly curved sacs (2·5 × 1·3 mm.) borne in clusters ([fig. 319], A–C) on slender ramifications of the fertile frond, which is characterised by the absence of a lamina. Each sporangium has a pedicel, and three to eight sporangia are attached to a common peduncle; the walls of the sporangia are at least two cell-layers in thickness and the annulus consists of a band of thick-walled cells passing from the crest down each side (figs. B and C), thus differing from the sporangia of Botryopteris ([fig. 319], D, F) in which the broad annulus is confined to one side.