28 F. E. FRITSCH. 



33. Lyngbya attenuata sp. b. 

 (PL IL, figs. 79-84.) 



Filis stratum definitum non formantibus, sed numerosis ad superficiem stratuum 

 Phormidli affixis vel repentibus, flexuosis, fragilibus ; vaginis achrois firmis tenuibus ; 

 trichomatibus inter cellulas baud constrictis, cellulis tarn longis quam latis vel paulo 

 brevioribus, cytoplasmate homogeneo dilute serugineo, dissepimentis pellucidis, valde 

 indistinctis ; apice tricbomatis plus minusve distincte attenuate, plerumque rotun- 

 dato, interdum paulo capitato, ssepe modice arcuato. 



Diam. fil. = 5-6 /x ; diam. trich. = 4 • 8-5 " 7 /x. 



Hah. — Pond in ice off Black Island, McMurdo Strait, December 31st, 1902 ; 

 Gap pond, Winter Harbour ; pond among the eskers which border the shore of the 

 Western mainland, December 2nd, 1902. 



The most distinctive character of this species lies in the marked attenuation 

 of the apex (figs. 79, 80), the terminal cell being sometimes somewhat inflated 

 and making the trichome capitate (figs. 82, 83) ; as a general rule the attenuated 

 apex is rounded, but occasionally the terminal cell is more or less pointed (figs. 

 81, 84). Iodine coloured the filaments a deep yellowish-brown, but left the apical 

 cell colourless. 



L. attenuata appears to come nearest to L. serugineo-ccerulea (Kiitz.) Gom., 

 from which it difi'ers in the following respects : the frequent curvature of the apex 

 of the trichome ; the rather longer cells ; the homogeneous cell-contents and the 

 absence of granules at the dissepiments ; the generally marked attenuation of the 

 end of the trichome, often beginning at some distance from the apex ; the absence 

 of special thickening of the outer membrane of the apical cell ; the very indistinct 

 septa. L. cladophorse Tilden (Minnesota Algae, I., Minneapolis (1910), p. 116, 

 PI. v., fig, 34) should also be compared. 



34. Lyngbya ^erugineo-ccerulea. 



4 



(PI. II., figs. 85-86.) . 

 Lyngbya arugineo-coerulea (Kiitz.) Gom., to7n. cit., pp. 146-147, PI. IV., figs. 1-3. 



Hab. — Abundant in Gap pond, Winter Harbour, on the surface of the 

 Phonnidium-sheets, where it often formed an appreciable stratum. 



In some cases the cell-contents were provided with abundant coarse granules 

 (fig. 85), in others some of the dissepiments were very markedly granulated (fig. 

 85a). In several of the samples from the Gap pond the filaments of this species 

 were forming gonidia, a single round gouidium being observed in each cell (fig. 86). 



