ULTRASTRUCTURE AND TAXONOMY OF THE GENUS ENDOPHYTON (ULVALES, ULVOPHYCEAE)

Fine structure of vegetative cells, development and morphology of spor angia and general morphology of zoospores were studied for the first t ime in the genus Endophyton Gardner. Vegetative cells contained one pa rietal perforate chloroplast with 2-4 ulvophycean pyrenoids and transv erse cell walls without plasmodesmata. Sporangial walls were formed by two distinct electron-dense and fuzzy layers which contained a contig uous electron-translucent, fibrillar material. Zoospores were naked, w ith an anterior dense aggregation of vesicles and a cup-shaped chlorop last with one eyespot. The flagellar apparatus showed 1800 rotational symmetry and counterclockwise absolute orientation of its components. Microtubular roots had a cruciate pattern, in which d = 2 and s = 4 wi th 3/1 arrangement. Electron-dense bilobed terminal caps covered the p roximal end of each basaI body. These observations support the suggest ed close relationship of Endophyton to the allied genus Entocladia and other ulvalean algae, and reinforce the criteria for including the ge nus in the class Ulvophyceae, order Ulvales, family Ulvellaceae.