Mr. J. Ralfs on the Diatomacese. 351 



Not unfrequently this species has the joints here and there di- 

 lated into a globular form as described by Kutzing ; in this state 

 it much resembles a species of Vesiculifera, Hassall ; and indeed 

 Mr. Hassall, whose researches have so much extended our know- 

 ledge of the freshwater Algse, was induced by this resemblance 

 to refer it to a subdivision of that genus, in one of his valuable 

 and interesting papers on the British freshwater Confervse ; but 

 since his paper was published he has agreed with me in opinion 

 that his V. composita is undoubtedly the Meloseii'a varians of 

 Agardh, and not a species of Vesiculifera. When the joints are 

 thus dilated, the central fun*ow gives the appearance of two 

 joints combining in the formation of the inflated cells. 



Plate IX. fig. 5. Meloseira varians. 



6. M. orichalcea, Kutz. Filaments slender ; frustules two to three 

 times longer than broad, marked with two central lines ; junction - 

 surfaces striated, closely united. Kutz. in Linnaea 1833, p. 71. 

 fig. 68. jGalUonella aurichalcea, Eh. Die Infus. p. 168. t. 10. fig. 6; 

 Pritch. Infus. p. 200; Bailey, Amer. Bacil. part 2. p. 5. pi. 2. 

 fig. 4 b. 



In freshwater ditches and slow streams. Cheshunt, Mr. Hassall ; 

 Stevenston, Ayrshire, Rev. D. Landshorough ; Dolgelley.^ 



Brownish when recent ; it becomes paler in drying. 



The filaments are finer than in M. varians ; joints two to three 

 times longer than broad, with two lines near the centre ; ends 

 closely united in the same manner as in M. arenaria, but the den- 

 tated appearance of the ends of the striae is less evident ; junc- 

 tion-surfaces flat with radiated striae, which are often very obscure 

 in the centre, but generally plainly developed round the margin. 



This species is likely to be mistaken for M. varians-, but its 

 filaments are more slender and more uniform in size, the joints 

 are longer, more closely united, and especially it difi'ers in having 

 two central lines and striated junction-surfaces, and in not turn- 

 ing green in drying. 



Kutzing figures this species with joints occasionally enlarged 

 in the same manner as in M. varians. 



Mr. Hassall first detected it in this country. 



Plate IX. fig. 6. Meloseira orichalcea. 



*** Filaments very slender ; joints obscure. 



7. M. ochracea. Frustules very slender, convex at each end, ovate, 

 not striated, ferruginous ; filaments often connected together in a 

 subramose manner. Gallionella ferruginea. Eh. Die Infus. p. 169. 

 t, 10. fig. 8. and t. 21. fig. 3 ; Pritch. Infus. p. 200. figs. 129, 130. 

 Conferva ochracea, Dill. t. 62 ! Oscillatoria ochracea, Grev. Fl. 

 Edin. p. 304; Harv. Br. Alg. p. 167. 



Pools and slow running streams, especially in boggy soils. 



