Halopteris diaphana (Heller, 1868)

Six short, simple, monosiphonic, stems connected by a thick, tubular hydrorhiza. Lower stem ahydrocladiate, with several transverse nodes, perisarc thick, thinning distally. Cauline nodes oblique, deeply V-shaped when viewed from front, the three or four proximal nodes thickened and transverse.Cauline hydrothecae proximal on internode, each internode with four nematothecae, one below the hydrotheca, two laterals beside the hydrotheca and one median above; a nematotheca in the axil of the hydrocladial apophysis.

Hydrocladia alternate, borne on a very short apophysis of the stem and bearing 2 - 4 hydrothecae. Proximal hydrocladial node transverse, distal node oblique, swollen below hydrotheca. Proximal hydrocladial internode athecate, succeeding internodes alternately thecate and athecate, the athecate internode with a transverse proximal and an oblique distal node, oblique node passing from below the hydrotheca to the median nematotheca, transverse node wide, below the twin lateral nematothecae. Perisarc of lower internodal wall very delicate.

Hydrotheca deep cup-shaped, occupying much of the internode, adcauline wall free for less than half its length, free part concave, widening slightly to the margin. Margin circular, oblique to internode, perisarc thinning at margin. Thecate hydrocladial internode with three nematothecae, one median subhydrothecal and twin suprathecal laterals.

Median nematothecae two-chambered, base robust, abcauline side convex, adcauline side recumbent to internode, cup excavated. Twin lateral nematothecae two-chambered, pedicel long, distal chamber large, bowl-shaped, facing forward and outward beyond the hydrotheca, adcauline side excavated. Cauline and axillar nematothecae the same as median hydrocladiate nematothecae.