80 



Chlorophycea' 



8. baeillaris Nag. (fig. 24 A) is an abundant species on damp earth, walls, 

 palings, etc. ; diam. of cells '1 3'8 p. S.flaccidus (Kiitz.) Gay (fig. 24 B) is 

 a larger species frequent on wet stones and in rain-pools; diam. of cells 

 710-5 fj.. 8. dissectus Gay (fig. 24 C) is a closely allied species to 8. Jlac<:iihis, 

 or perhaps only a form of it. S. variabilis West & G. S. West (fig. 24 D) 

 forms a thin green stratum on wet stones in the neighbourhood of waterfalls ; 

 the cells are very irregular in outward form and the chloroplast is often devoid 

 of a pyrenoid or may even possess two ; diameter of cells 3 6 p. 



Genus Uronema Lagerh., 1887 1 . The filaments are simple, 

 relatively short, and destitute of a mucous coat ; they consist of 

 cylindrical cells, the apical cell being acuminate and the basal cell 

 attenuate. The plants are fixed by a disc secreted by the basal 



cell. The chloroplast occupies a con- 

 siderable area of the cell-wall and is 

 parietal, containing two pyrenoids. The 

 cell-wall is firm and thin. 



The zoogonidia are produced singly 

 or in pairs from each cell; they possess 

 four cilia and a subapical pigment-spot. 

 Sometimes the zoogonidia are arrested 

 in their escape, the cilia are not de- 

 veloped, and an aplanospore is produced 

 by the acquirement of a strong cell- 

 wall. 



The only species is U. confer vicoluin Lagerh. 

 with filaments 4 6 p. in diameter and cells 

 2 3 times longer than broad. It is an ex- 

 ceedingly rare plant, distinguished from species 

 of Ulothrix by its short filaments, by the 

 attenuation of the apical and basal cells, by 

 the chloroplast, and by the firm cell- walls. I 

 have only met with it in abundance from the 

 Orkney and Shetland Is. 



The genus Rhaphidonema Lagerh. 

 (of which R. nivale is known from W. Yorks.) is a fungus. 



Genus Binuclearia Wittr., 1886 2 . The filaments are simple 

 and attached when young by a hapteron from the basal cell. The 

 cells are cylindrical with firm, distinctly lamellose cell-walls, the 

 transverse walls being unequal, a thin one and a very thick one 

 alternating. The cells thus appear to be arranged in pairs. The 



1 Lagerh. in Malpighia 1887, p. 518, t. xii, f. 110. 



- Wittr. in Wittr. and Nordst. Alg. Exsic. 1886, no. 715. See also Schroder in 

 Forschimgsberichte aus der biol. Station zu Plon, Teil vi, 1898, p. 1921. 



Fig. 25. A E, Binuclearia 

 tiitrini/1 Wittr., from Lewis, 

 Outer Hebrides ( x 440). 



