STUDIES ON DASYACEAE .2. A REVISION OF THE GENERA EUPOGODON AND DIPTEROCLADIA GEN. NOV. (CERAMIALES, RHODOPHYTA)

Dipterocladia YSDM de Jong gen. nov., a genus containing marine red al gal species belonging to the Dasyaceae, Ceramiales, formerly put into Eupogodon Kutzing, is described and a revision of the genus Eupogodon is presented. Dipterocladia forms a monosiphonous pseudolateral and a polysiphonous determinate sympodial lateral on each segment of the mai n axis in a pairwise distichous manner, a branching form which is uniq ue within the Dasyaceae. The new genus has an alternating counterclock wise sequence of periaxial cell formation, a distichous alternating br anching symmetry, a bilateral organisation, post-sporangial cover cell s and monosiphonous pseudolaterals arising from each axial segment. Di pterocladia is accepted to include two species: Dipterocladia pinnatif olia (Suhr) YSDM de Jong and D. pulchella (Weber-van Bosse) YSDM de Jo ng. Features of the female reproductive system of Eupogodon planus (C. Agardh) Kutzing are described here for the first time and this system appears to be similar to that described for E. spinellus (C. Agardh) Kutzing. Detailed observations of the growing tip of Eupogodon planus reveal a secondary bilateral organisation of the axes and periaxial ce lls cut off in a circular clockwise sequence. Maintenance of the tradi tional genus Eupogodon is proposed. Eupogodon is defined by features o f the tetrasporangial stichidia, including the numbers of tetrasporang ia developed in each fertile segment (7 to 9) and a polysiphonous, sub sessile insertion of the stichidia and by the typical 'spine-like' pol ysiphonous base of the pseudolaterals. Eupogodon is accepted to includ e five species: Eupogodon apiculatus (C. Agardh) Silva, E. penicillatu s (Zanardini) Silva, E. planus, E. spinellus and E. tenellus (Weber-va n Bosse) Silva. An overview and a key of the family Dasyaceae is provi ded, using vegetative structures.