292 IVes^ : Phytoplankfon of English Lake District. 



cell. 16-25 J".; lat. cell. 3-4 /j^-; long, colon. 130-340 /y.; lat. 

 colon. 13-48 ju.. (Fig. 6 a-d.) 



Wille has also described an American species — Elakatothrix 

 americnna — with shorter and broader cells [vide ' Wille in 

 Rhodora/ Aug. 1899, p. 150). 



Bacillarie^. 



20. Rhizosolenia morsa W. & G. S. West in ' Trans. 

 Roy. Irish Acad.', XXXIII., sect. B., part II., 1906, p. 109, 

 t. II, f. 5 — 7. R. eriensis H. L. Smith var morsa W. & G. S. 

 West in ' Trans. Roy. Soc. Edin.', XLL, part III., 1905, p. 509, 

 t. 6, f. 23. 



This Diatom occurred in abundance in Thirlmere and 

 W^indermere. It is now known to occur in all the British lake- 

 areas, and also in the Australian plankton. In the June plank- 

 ton of Thirlmere resting-spores were noticed. These were 

 relatively small, and were formed towards the middle of the 

 cell. They were broader than long, and furnished with strong 

 walls. Long. spor. 9 jj. ; lat. 12 /a. (Fig. 2). 



21. Tabellaria fenestrata (Lyngb.) Kiitz. var. as- 



TERIONELLOIDES Grun. 



This plankton-variety is fairly general in the English lakes 

 and the elongated form of the frustules is maintained much 

 more constantly than in the Scottish lakes. In the plankton 

 of Grasmere colonies with very long frustules were plentiful. 

 Long, trust. 86 />i ; diam. colon. 170 /x. 



The first British record of this variety was in 1902, when we 

 recorded it from Lough Neagh and Lough Beg, but since then 

 it has been found abundantly in all the lake-areas. 



Myxophyce.e. 



22. Lyngbya bipunctata Lemm. in * Forschungsb. Biol. 

 Stat. Plon.', VL, 1900, p. 138, t. 2, f. 48 ; ibid. X., 1903, p. 152. 



This species was frequent in both Codale and Easedale 

 Tarns. Diam. trich. 1.4 ju, ; long, cell, 4-5.5 /*. Close to each 

 end of every cell is a strongly refractive granule, the rest of the 

 cell-contents being homogeneous, and of a pale blue-green 

 colour. The filaments were flexuose, but not twisted into any 

 regular spirals, as is sometimes the case. It appears to be 

 very closely allied if not identical with L. Lagerheimii (Mob.) 

 Gomont. The narrow plankton-species of Lyngbya require 

 further investigation and considerable revision. 



[To be cojitinned). Nstms 's;. 



