On the fertile tetrasporic phase of Cottoniella Boergesen (Ceramiales, Rhodomelaceae, Sarcomenioideae)

The authors point out the presence near Augusta (Siracusa, Sicily) of fertile tetrasporophytes of Cottoniella filamentosa (Howe) Boergesen var. algeriensis (Schotter) Womersley and Shepley (Ceramiales, Rhodomelaceae, Sarcomenioideae). Tetrasporocysts, tetrahedrally divided, lie in two parallel rows in branches of indefinite growth. They are produced by the two lateral pericentral cells of each axial cell. Some taxonomic reflections and a key to the species of Cottoniella complete this work.