PHYTOFLAGELLATES 115 



A few relevant observations on the flagellated reproductive 

 cells of brown algae may be interposed here, since these cells show 

 considerable resemblance to chrysomonads. The stigma-flagellum 

 relationship in the spermatozoid of Fucus (Manton and Clarke, 

 1956) has been mentioned in Chapter 2. A particularly interesting 

 situation exists in the spermatozoid of Dictyota (Manton, 1959b), 

 where the uniflagellate cell conceals a second kinetosome, adjacent 

 and nearly parallel to the flagellum-bearing one but ending blindly 

 below the cell membrane. From the base of the flagellum-bearing 

 kinetosome arises a fibrous rhizoplast which descends towards 

 the nucleus, passes near its surface without making contact, then 

 runs past one or more mitochondria that may be flattened against 

 it, and finally ends just under the cell membrane. In Fucus, the 

 two kinetosomes are nearly parallel but point in opposite direc- 

 tions ; they seem to be in firm contact with each other and laterally 

 with the nuclear surface. From the apposed surfaces of the 

 kinetosomes a strand passes to the stigma and another toward 

 the fibrous anterior proboscis; no rhizoplast is apparent. In all 

 of these cells, mitochondria are microtubular. 



Cryptomonadea, Dinoflagellatea 



We come now to two well-defined phytoflagellate classes that 

 often are considered to be related to each other but show no clear 

 affinities with any other phytoflagellate groups. They usually are 

 placed provisionally with the brown stock (Hutner and Provasoli, 

 1951), but their pigment complements are in some ways inter- 

 mediate between these and the greens (Dougherty and Allen, 

 1959, 1960). Although the dinoflagellates are enormously 

 abundant both in species and in individuals in marine and fresh 

 waters, and as symbiotes in other organisms, they have not been 

 sufficiently studied with the electron microscope to provide any 

 conclusions of general significance. For the cryptomonads, a 

 small class but one that includes some familiar laboratory species, 

 we know even less ; only their flagella and trichocysts have been 

 examined. 



At present writing, the author is aware of only one report 

 concerning the ultrastructure of unquestionable dinoflagellate 

 flagella. This resulted from a cursory examination of osmic-fixed 



