COMPARATIVE CYTOLOGY AND TAXONOMY OF THE ULVAPHYCEAE. I. THE ZOOSPORE OF<i>ULOTHRIX ZONATA</i>(CHLOROPHYTA)¹

Abstract

ABSTRACT This fine structural study of the quadriflagellate zoospore of Ulothrix zonata (Weber &amp; Mohr) Kützing, with special attention to the flagellar root system, demonstrates that it is very similar to the zoospore of Ulva lactuca L. in several aspects. Common features include the presence of a cruciate root system (4‐2‐4‐2 type), a non‐striated band that connects basal bodies, a so‐called terminal cap, and system I and system II striated root components. Only slight differences exist, i.e. in the shape of the terminal cap, and in the number and position of the system II root components. It is concluded that the taxonomic affinities of U. zonata lie with the Ulvaphyceae sensu Stewart and Mattox rather than with the Chlorophyceae. Additional support for this conclusion is the discovery of tiny, flat body scales on the zoospore of U. zonata. A summary of the distinctive characteristics of the Chlorophyceae, Charophyceae and Ulvaphyceae reflecting the current state of knowledge is given.