Algae. 1992; 7(1): 13-26.

Taxonomic Features of Polysiphonia morrowii Harvey (Ceramiales, Rhodophyta)

Toshihiko Kudo, Michio Masuda

Biological Laboratory, Sapporo University, Department of Botany, Faculty of Science

Taxonomic features of Polysiphonia morrowii Harvey were investigated through its life history stages by laboratory culture experiments and periodic field observations. Some of the taxonomic features adopted previously show phenotypic variation according to environmental conditions or growth stages : the external appearance of individuals, length/diameter ratios of segments, and number of axillary tetrasporangial branchlets. The significant specific features of P. morrowii were confirmed in this investigation. This species is characterized by the following features: (1) thalli composed of upright axes and tightly, intricately entangled stolons, (2) ecorticated thalli with four pericentral cells, (3) thick and setaceous thalli in the mature stage, (4) non-septate advantitious rhizoids, (5) sharply pointed ultimate branchlets, (6) endogenous axillary branchlets formed from the central axial cells, (7) a few trichoblasts in the mature stage, (8) tetrasporangia formed both on the ultimate and axillary branchlets, (9) axillary tetrasporangial branchlets in tufts (7-8 in number) on the axils of fully mature plants, (10) spermatangial branchlets replacing whole of a trichoblast, and (11) urceolate cystocarps.

Keywords : Ceramiales, Polysiphonia, Polysiphonia morrowii, Polysiphonia senticulosa, Rhodomelaceae, Rhodophyta, taxonomy