Synthecium campylocarpum Allman, 1888

Stems to 100 mm high.

Hydrorhiza tubular, reptant on host, perisarc of hydrorhiza and stems thick. Stems wide proximally, narrowing distally, proximal internodes usually athecate, internodes thereafter long with one to three pairs of distal hydrothecae; hydrocladia opposite, distal on internode, given off at an angle of 60° - 90° to caulus above cauline hydrothecal pair; nodes transverse, distinct in younger parts of stems, indistinct to completely absent from older parts, sometimes a secondary node between primary nodes.

Hydrocladia on a long vasiform apophysis, sometimes a transverse distal node below first hydrothecal pair.

Hydrothecae opposite, occupying almost or entire internode, nodes vestigial or absent, hydrothecae often in contact vertically, a little separated in front, in contact behind; hydrotheca tubular, adcauline wall smoothly convex, one fifth to one quarter of wall free of internode, abcauline wall straight or slightly tumescent proximally, becoming concave, curvature increasing distally, perisarc thinning a little towards margin. Margin circular, sinuous, facing slightly forward, parallel to hydrocladial axis or tilted slightly upward, rim outrolled, sometimes up to four renovations from within hydrotheca.

Colonies dioecious, gonothecae borne on lower stem and hydrocladia. Male gonotheca long, irregularly pod-shaped, usually widest about middle, pedicel inserted with a right-angled bend deep into hydrotheca, often splitting hydrotheca; perisarc of gonotheca rather thin, smooth to faintly undulated, orifice small, circular, operculum a thin sheet of tissue, gonophore elongate. Female gonotheca small, lenticular, one side usually flat, other side convex, perisarc thicker than male, six to eight transverse ribs crossing entire body, more deeply incised on flatter side, ribs fading out proximally and distally, orifice small, circular, on a short tubular neck, neck foreshortening as gonotheca matures.

Cnidome of large ?haplonemes with blunt ends, capsule 62.5 x 17.5 µm, tubule coiled, in tentacles and coenosarc of stems.

Colour: Colonies yellow; female gonophore orange.