FRESHWATER ALG.E. 35 



There was occasionally very little constriction between the cells. Some of the 

 filaments bore apical bacterial clusters. 



50. OSCILLATORIA FORMOSA. 



Oscillatorin formosa Bory, Diet, class, d'kist. nat., xii. (1827), p. 474; Gomont, torn, cit., pp. 230-231, 



PI. vii., fig. ic. 



Diam. trich. = 5 /A. 



I Tab. Damp spot, summit of Cape Aclare, January 9th, 1902. 



This form occurred in tufts attached to the surface of Prasiola crispa. The 

 trichomes showed no indication of constriction at the dissepiments, but Gomont's 

 figure also shows nothing of the kind. Although many of the trichomes were 

 tapering and hooked, others in the same tuft were straight at the apex, not tapering 

 and obtuse. The trichomes often exhibited a slight terebriform character (cf. 0. 

 Borge, Algen aus Argentina und Bolivia, Arkiv f. Botanik, VI., No. 4 (1906), p. 11). 



51. OSCILLATORIA PRODUCT A. 



(PI. I, fig. 65.) 

 Oscillatoria producta W. and 0. S. West, op. cit., p. 294, PI. XXV., figs. 86-90. 



Ilab. Freshwater pond among eskers, four miles north of Black Island, upon 

 ice, McMurdo Strait, September 12th, 1902. 



Only a few trichomes of this species were seen. They were quite straight 

 with a straight tip, which was rather longer than shown in any of Messrs. West's 

 figures (cf. fig. 65). The cell-contents were highly granular. 



52. OSCILLATORIA BREVIS. 



Oscillatoria brevis Kiitz., Pliyc. gen. (1843), p. 186 ; Gomont, torn, cit., pp. 229-230, PI. VII., figs. 14, 15. 



r 



Diam. trich. = 4-7 p. ; cellulis diametro ij iplo kmgioribus. 



Ilab. Freshwater pond among eskers, four miles north of Black Island, upon 

 ice, McMurdo Strait, September 12th, 1902 ; pond among eskers, bordering shore 

 of Western Mainland, December 2nd, 1902. 



The trichomes were frequently interrupted by inflated masses of intercellular 

 substance. 



53. OSCILLATORIA DEFLEXA. 

 Oscillatoria deflexa W. and G. S. West, op. cit., p. 295, PI. XXV., figs. 95-97. 



Hob. Freshwater pond in ice, off Black Island, McMurdo Strait, December 

 31st, 1902 (floating among Nodularia koettlttzi and Oscillatoria tennis). 



