Comparative cytology and taxonomy of theUlvaphyceae II. Ulvalean characteristics of the stephanokont flagellar apparatus ofDerbesia tenuissima

Summary The stephanokont flagellar apparatus of the zoospores ofDerbesia tenuissima (De Not.) Crouan is examined and compared to the flagellar apparatuses of other green algae. The flagella ofDerbesia are attached to two of three bands which lie at the junction of the body and papilla. Serial longitudinal and cross sections reveal that the basal bodies are attached to the bands along their sides and at their proximal ends. The bands are not striated in any plane. The lack of striation in the bands and the partial covering of the proximal end of the basal bodies by one of the bands closely resemble the type of flagellar connection system described as the Bryopsis-type byMelkonian (1980). Zoospores of ulvalean green algae also possess these features, suggesting that green siphons are phylogenetically related to theUlvales. It is proposed that green siphons be tentatively classified in theUlvaphyceae rather than in theChlorophyceae orCharophyceae.This work supported by NSF Grant DEB 78-03554.