Stem reaching a diameter of about 6–8 cm., with internodes 6–12 cm. in length, the surface either smooth or faintly ribbed. Primary branches given off in opposite pairs from the nodes, the lateral branches giving off smaller branches disposed in the same manner. The smaller branches bear verticils of leaves at each node; both leaves and ultimate branches being in one plane. The leaves are narrow, lanceolate-spathulate in form, broadest about the middle, 1–5 cm. in length and 1–3 mm. broad, hairy on the upper surface[669]; each leaf is traversed by a single vein.
Fig. 88. Branch of Annularia stellata (Schloth.). ⅘ nat. size.
From a specimen in the Collection of Mr R. Kidston. Upper Coal-Measures, Radstock.
Each whorl contains 16–32 segments, which are connected basally into a collar or narrow sheath; the lateral segments are usually longer than the upper and lower. The branches are about 6–20 mm. broad, with finely ribbed internodes 3–7 cm. long, bearing verticils of leaves; the ultimate branches arise in pairs in the axils of the lateral segments of the verticils.
The strobili are of the Calamostachys[670] type and are borne on the main branches or possibly on the stem; they have a long and narrow form and are attached in verticils at the nodes. Each strobilus consists of a central axis bearing alternate whorls of linear lanceolate sterile bracts and sporangiophores, about half as numerous as the sterile bracts; each sporangiophore bears four ovoid sporangia.
The anatomical structure of a specimen referred to Annularia stellata has been described by Renault[671]. The cortex consists of parenchyma traversed by lacunae and limited peripherally by a denser hypodermal tissue. In the stele Renault describes 14 xylem strands, each with a large carinal canal. The pith was apparently large and hollow. The same author describes an Annularia strobilus in which the lower sporangiophores bear macrosporangia, and the upper microsporangia.
Fig. 89. Annularia sphenophylloides (Zenk.).
A. Strobilus (Stachannularia calathifera, Weiss). ⅔ nat. size. B. Vegetative shoot. ⅘ nat. size.
From specimens in the Collection of Mr R. Kidston. Upper Coal-Measures, Radstock.
The references in the footnote should be consulted for figures of this species of Annularia; it is from the examination of such specimens as are referred to in the note that the above diagnosis has been compiled[672].
Annularia sphenophylloides (Zenk.). Fig. 89.