A re-examination of the morphology and reproduction of Nothocladus lindaueri (Batrachospermales, Rhodophyta)

SUMMARY The vegetative morphology and reproduction of the freshwater rhodophyte Nothocladus lindaueri Skuja [=Batrachospermum lindaueri (Skuja) Necchi et Entwisle] were examined by light and electron microscopy. It was confirmed that this alga has a typical batrachospermalean pit plug with two cap layers, the outer one of which is domed. During elongation of hair cells, the primary wall is broken, forming a basal collar. Hair cells have a single nucleus and abundant Golgi bodies, en‐doplasmic reticula (ER) and vesicles. Dividing apical cells of the fascicles have a nucleus with art adjacent zone of exclusion, the latter containing a single polar ring. Branched trichogynes and fertilized carpogonia are shown for the first time in this species. Carpogonial branch and involucral cells contain a prominent axial nucleus, proplastids, ER and vesicles. The pit plugs disintegrate among these cells leaving open pit connections. Carpogonia have plentiful mitochondria and vesicles. The wall at the trichogyne apex is thickened and densely stained. The carposporophyte centre consists of a mass of fusion cells with open pit connections, and indeterminate gonimoblast filaments arise from this mass. The combination of a symmetrical carpogonial base, a carposporophyte centre consisting of a mass of fusion cells, and exclusively indeterminate gonimoblast filaments appears to be unique among the members of the Batrachospermaceae. The specimen of N. lindaueri contains epiphytic filaments of Audouinella meiospora producing both spermatangia and monosporangia. Spermatium formation in N. lindaueri remains unknown.