Monostaechas
Diagnostic description:
Colony with or without erect stems; stem if present polysiphonic, composed of interconnecting tubes of equal diameter and importance, irregularly giving rise to hydrocladia, if stem absent, hydrocladia arising directly from hydrorhiza; hydrocladia branched or forming a sympodium, each successive hydrocladium originating from the posterior surface of the ahydrocladiate segment of the previous hydrocladium, typically all branches directed to the same side; hydrotheca cup-shaped, margin entire, nematothecae two-chambered, movable; gonophores fixed sporosacs, gonothecae of two sexes often present on same colony.