334 



MyxophycecB 





Genus Symploca Klitz., 1843. In this genus the filaments 

 are densely interwoven to form a creeping stratum from which 

 arise numerous erect tufts of variable height. A false branching 

 is exhibited by the filaments of some species, the branches arising 

 singly. The sheaths are thin, hyaline, and generally firm; they 

 partially coalesce in the erect tufts. Only one trichome is present 

 within a sheath and its apex is straight. 



S. muralis Kiitz. is known from W. Yorkshire. It occurs on damp earth, 

 walls, or trunks of trees; thickness of trichomes 3'4 4/j,; fig. 152 B and C. 

 Other species occur among mosses and dead leaves, and others in hot springs, 

 the genus having a world-wide distribution. 



Genus Lyngbya C.Ag., 1824. [Leibleinia Endlicher, 1836 ; 



Leptothrix Klitz., 1843 

 (in part) ; Spirocoleus 

 Mobius, 1889 (in part).] 

 The filaments are un- 

 branched, free-floating or 

 densely intricate, forming 

 a floccose mass or an 

 expanded stratum. The 

 sheaths are firm, of vari- 

 able thickness, and some- 

 times lamellose. They 

 are generally hyaline, but 

 in a few species they 

 become of a yellow-brown 

 colour. The trichomes 

 are either obtuse or 

 slightly attenuated at 



Fig. 153. A, Lyngbya major Menegh., from 

 Wimpole Park, Cambridge. B and C, L. ceru- 

 gineo-ccerulea (Kiitz.) Gom., from Bradford, W. 

 Yorks. D, Pkormidium iiiolle (Kiitz.) Gom. (a 

 narrow form), from Bradford, W. Yorks. E and 

 F, Ph. tenue (Menegh.) Gom., from Wicken Fen, 

 Cambridge. (All x 460.) 



the apices, and sometimes 

 there are evident constrictions between the cells. 



Species of this genus are widely distributed and occur in very varied 

 habitats. Those belonging to the subgenus Leibleinia are entirely marine 

 and live as epiphytes on other larger Algse. There are about 10 British 

 freshwater species, of which L. Martensiana Menegh. (thickness of trichomes 

 6 10 fi) and L. cerugineo-coerulea (Kiitz.) Gom. (thickness of trichomes 

 46 /u ; fig. lf)3 B and C) are the most abundant. L. ochracca (Kiitz.) Thur. 

 occurs in water containing much iron, the oxide of iron ultimately forming a 

 thick deposit round the sheaths of the filaments. L. cestuarii (Mert.) Liebman 

 is the largest British species which occurs in fresh water (thickness of tri- 

 chomes up to 24 p.), although it is principally brackish or marine in habit. 



