On a new species of Annularia from New South Wales
Abstract
Stem slender, articulate; leaf-whorls and stem approximately in the same plane; whorls consisting of about thirty leaves, each leaf being joined to the neighbouring ones for half or more of its length. Leaves narrow, wedge-shaped and straight, greatest width near apex, which is obtusely rounded and prolonged into a mucro; traversed by a single prominent vein. In the specimen there are remains of several leaf-whorls, two of which (PI. viii, fig. 1) are adjacent whorls, with portion of the stem joining them preserved. This stem is about 1·5 mm. broad and the internode is about 2.5 cm. in length. The leaf whorl forms an almost continuous lamina, roughly circular in outline, adjacent whorls overlapping slightly; the leaves are joined for a little more than half their length, and are quite close together for the remainder. There are about thirty leaves in a whorl, the individual leaf being narrow, wedge-shaped and straight, about 15 mm. long and about 2 mm. wide at the widest part, which is some 2 mm. from the apex. Each leaf has a distinct midrib which shows as a very fine projecting line in the specimen. This fine line is usually in the middle of a narrow dark band some quarter of a millimetre wide, often widening slightly towards the apex of the leaf. In the few cases in which the apex of the leaf is preserved there is distinct indication of its prolongation as a mucro (PI. viii, fig. 2), as in the specimens figured by Walton (1936, pls. 31, 32). There are a number of irregular markings diverging from the midrib (PI. viii, figs. 3, 4), which possibly represent the markings on the leaf surface mentioned by Halle (1928, p. 239, pl. i, fig. 9) as being present on the adaxial side of leaves of Annularia sphenophylloides—the side of the leaf which, he suggested, faced upwards. Halle regarded these as representing hairs on the leaf surface, but Walton (1936, p. 231) considers them to be due to the presence of a "system of elongated darker structures of cellular dimensions" in the substance of the lamina. The appearance of the leaf impression in our specimen is very like that figured by Walton for Annularia Jongmansi (1936, pl. 31, figs. 12, 13).
