1907.] 



Fresh-water Algal Flora of Ceylon. 



237 



Microspores, and Zygnema are all casual forms in these pools, these being the 

 only habitats in which species of Ulothrix occur at all commonly in the 

 island. Of much greater importance for the characterisation of the ferru- 

 ginous pools are certain Desmids (fig. 3) and Diatoms. Foremost among 



Fig. 3. — A few of the more Characteristic and Typical Desmids of the Ferruginous Pools 

 (all magnified about 260 diameters). A, Pleurotamium Trabecula (Ehrenb.), Nag. 

 B, Euastrum ansatum, Ralfs. C, Euastrum obesum, Joshua f. punctatum. D, Pleuro- 

 tcenium annulatum, West and West. E, Closterium Venus, Kiitz forma. F, C. pseudo- 

 diance, Roy. G, C. selaceum, Ehrenb. H, Netrium digitus (Ehrenb.), Itzigs. and 

 Rothe. J, Hyalotheca dissiliens, Breb. K, Gymnozyga moniliformis, Ehrenb. 

 L, Closterium abruptum, West. M, Pleurotcenium nodosum, Lund. N, Triploceras 

 gracile, Bail. 



the Desmids are species of Pleurotcenium (P. Trabecula (Ehrenb.), Nag. ; 

 P. annulatum, West and West ; P. trochiscum, West and West ; P. nodosum, 

 Lund. ; P. doliforme, . West and West, etc.) ; diverse forms of Triploceras 

 gracile, Bail. ; species of Closterium (C. setaceum, Ehrenb. ; C. abruptum, 

 West ; C. Pseudodiance, Roy ; C. Venus, Kutz, etc. ; in the uplands, also : 



T 2 



