154 University of California Puhlimtions in P>otan\j [Vol.8 



3. Filamoiits piiinatoly branched 4. Bryopsidaceae (p. 156) 



3 Filaments irregularly or dichotomously branched 4 



4. Sexual reproduction anisogamous; zoospore single, covered with cilia 



7. Vaucheriaceae (p. 177) 



4. Sexual reproduction unknown; zoospores several in a sporanjiiuiii, provided 

 with a crown of cilia 5. Derbesiaceae (p. 163) 



FAMILY 3. PROTOSIPHONACEAE blackman and taxsley 



Thallus small, more or less globular, with or without colorless 

 rhizoids or pedicels, unseptate in vegetative condition ; nuclei several ; 

 chromatophore single and reticulate, or several, with or without pyre- 

 uoids; multiplication vegetative, by aplanospores, through micro- and 

 macro-zoospores, and possibly also through isoplanogametes. 



Blackman and Tansley, Rev. Class. Green Alg., 1902, p. 315; 

 Collins, Green Alg. N. A., 1909, p. 153; West, Algae, vol. 1, 1916, 

 p. 223. 



A small famil}- separated by Blackman and Tansley from the 

 Botrydiaceae to contain particularly^ Protosiphon Klebs as a segregate 

 from Botrydiutn Wallroth which, in turn, was removed from the 

 Isokontae to the Heterokontae. Besides Protosiphon, it is usually 

 made to include Blastophysa Reinke and Halicystis Aresch. The 

 result is a not over homogeneous assemblage and one not readily or 

 satisfactorily to be defined. Our only representative is Halicystis 

 ovalis (Lyngb.) Aresch, which is described further on. 



4. Halicystis Aresch. 



Thallus globular to ovoid, unseptate, multinucleate, with penetrat- 

 ing rhizoidal portion; chromatophores small, disk-like, destitue of 

 pyrenoids; asexual reproduction by 2-ciliated zoospores without 

 stigma, escaping through one or more openings ; similar but smaller 

 zoospores or zoogametes( ?) formed in separate individuals; after the 

 emission of the spores the openings close and several new generations 

 of spores can be similarly produced. 



Areschoug, Phyc. Scaiid., ])art II, 1850, p. 446; Collins, Green 

 Alg. N. A., 1909, p. 372. 



A genus of two marine species of the northern oceans, seemingly 

 occurring in both the north Atlantic and the north Pacific. It has 

 been separated from Valonia because the vegetative body consists of 

 an unseptate coenocyte of an ovoid shape with short pedicel and 



