Spore germination of Ceratopteris thalictroides (L.) brongn

Germination of the spores of Ceratopteris thalictroides was examined by light and scanning electron microscopy. Spores germinate by scission of the spore coat at the trilete markings. The initial cell divisions produce a proximal prothallial initial with rhizoids that are distal and lateral. This represents a reverse orientation of the more common situation in ferns. Evidence is presented that rhizoid initials divide with the most lateral of the daughter cells differentiating into a rhizoid. Rhizoids are long and unbranched. The uniseriate protonema is transient with bi-dimensional growth established quite early. About a week following germination, the gametophyte is broad at the basal region and narrow at the anterior region. Further growth of cells in the basal region is by elongation and the anterior region broadens to produce an elongate-ovate gametophyte.