46 



Phwophycece 



Fig. o. Hydrurus 

 fostidus (Vill.) Kirchn. 

 A, nat. size. B, zoogoni- 

 dium (after Lagerheim). 



Genus Hydrurus Ag., 1824. The plants are branched colonies 

 of unicellular units embedded in a tough, cylindrical mucilage. 

 They vary from about 5 to 30 cms. in length 

 and are of an olive green colour. The 

 whole colony is simple below but branched 

 above, often cut up into fine penicillate 

 divisions, and covered with small villous 

 projections giving it a plumose appearance. 

 The entire structure behaves almost as a 

 multicellular plant, growth in length being 

 entirely dependent on single apical cells, 

 and the branching is usually monopodial. 

 The cells are commonly ellipsoidal and are 

 more densely crowded in the small branches 

 than in the main stems and branches. After- 

 wards the cells elongate and become ar- 

 ranged more or less in longitudinal groups. 

 H. foetidm (Vill.) Kirchn. is found attached to stones and rocks in 

 mountain streams. It is a sticky plant and gives off an offensive odour when 

 alive. It is common in Central Europe and in the Arctic regions when the 

 snows melt in the spring, but in the British Islands it is of very rare occur- 

 rence, being known only from Yorkshire and Scotland. 



Family 2. CHRYSOMONADINACEJE. 



These are unicellular or colonial organisms which in the free 

 condition are motile. Each individual 

 consists of an oval or elongated cell, with 

 either one or two cilia and either one or 

 two brownish-green chromatophores. A 

 red pigment spot is generally visible. The 

 cells increase by longitudinal division. 



Genus Synura Ehrenb., 1838. This is 

 a small, globose, free-swimming colony, 

 formed of a variable number (from 10 to 

 50) of ovoid or ellipsoid, biciliated indi- 

 viduals. They are arranged close together 

 in a radial manner, and each individual possesses two chromato- 

 phores and at the hinder end two pulsating vacuoles. 



Synura Uvella Ehrenb. (fig. 6) is commonly found in small ditches and 

 pools, particularly if they are of rain-water. Pure collections of it can be 

 frequently obtained in the early summer. 



Fig. 6. Synura Uvella 

 Ehrenb. Single colony 

 (x400), from Eldwick, 

 W. Yorks. 



