PHYTOFLAGELLATES 111 



Synura are composed of small cells with elongate stalks radiating 

 from a common center. Body and stalk are covered with over- 

 lapping siliceous scales shaped like oval hat brims with narrow 

 peaked crowns. The scales clearly are superficial; they lie outside 

 the cell membrane and contain no protoplasm. The stalks contain 

 low-density protoplasm continuous with that of the cell bodies. 

 In the ovoid cell, the two large, curved plastids are symmetrically 

 placed with the nucleus and a large leucosin vacuole between 

 them. No pyrenoids or stigma are observed. Microtubular 

 mitochondria are scattered through the cell but more numerous 

 near the basal bodies of the two flagella. The latter are of conven- 

 tional structure, with a transverse septum occurring at the level 

 of the cell surface where the central flagellar fibrils appear. From 

 the base of at least one of the kinetosomes, two or more obliquely 

 striated fibers, like the rhizoplast of Chromulina, pass posteriad to 

 the conical apex of the nucleus, where they branch out and spread 

 along the nuclear surface like an "enveloping string bag". Other 

 slender, unstriated roots apparently pass from the kinetosomes 

 upward and outward to unknown destinations. 



Again as in Chromulina, a distinct Golgi apparatus is found in 

 a constant location beside the rhizoplasts. Of the two flagella, the 

 longer, pantoneme one has an expanded sheath within which the 

 axial fiber bundle is eccentrically placed. Where the planes of 

 symmetry of the two flagella are discernible near the body of the 

 organism, they appear to be identical; that is, a single plane bisects 

 both flagella. 



Paraphysomonas vestita is a non-pigmented relative of Ochromonas 

 and is efficiently phagocytic — a rather neat trick for a cell that is 

 covered with long-spined scales. General cytoplasmic organiza- 

 tion is similar to that of other chrysomonads. From the sides of 

 the two anterior kinetosomes, several bundles of cross-striated 

 fibrils pass down to the adjacent, pointed, anterior tip of the 

 nucleus and along its sides. Nearby, on one side of the nucleus, 

 lies the extraordinarily large, well-developed Golgi body, with 

 extensive flat sacs and abundant peripheral micro vesicles. The 

 contractile vacuole is identifiable and has been described in 

 Chapter 2. 



Poteriochromonas stipitata, a solitary ochromonad that, like many 

 of its relatives, indulges in both photosynthesis and phagotrophy, 



