34 F. E. FRITSCH. 



no way attenuated ; the apical cell was more or less hemispherical, its outer membrane 

 being unthickened or barely thickened. The trichomes were frequently overgrown by 

 filaments of the subjacent Phormidium, which were in part very closely applied to the 

 Oscillatoria (fig. 64). Not uncommonly the apices of the trichomes bore a small 

 cluster of Bacteria (fig. 63). 



Apart from these typical specimens of the variety two peculiar forms were 

 noticed. In the one the apical cell of the trichome is produced into a point (f. 

 acuminata, fig. 62), although such cases were very rare. The other form is 

 characterised by a tendency for the trichomes to coil up into a spiral or for 

 two parts of a trichome to become twisted spirally around one another, somewhat 

 as in SjnruUna duplea: Wolle (f spiralis, cf. fig. 61). 



48. Oscillatoria koettlitzi sp. n. 

 (PI. I., figs. 55-59.) 



Trichomatibus rectis vel modice flexuosis, sparsis in superficiem Phormidii repen- 

 tibus, obscure violaceis, haud vel vix inter cellulas constrictis, 7-9 /x, crassis ; cellulis 

 valde deplanatis, longitudine l5-2plo latioribus (long. cell. 3-4" 5 ja), contentu 

 cum paucis granulis, dissepimentis ssepe indistinctis, granulis protoplasmaticis siBpe 

 magnis et fere confluentibus obductis ; apice recto, non attenuato, plerumque distincte 

 capitato ; cellula apicali ssepe decolorata, sine granulis et plus minusve inflata, 

 membrana superne interdum modice incrassata. 



Hah. — Gap pond, Winter Harbour; dry ponds, Winter Quarters, February, 

 1902. 



This species finds its place in Gomont's section Principes and is perhaps most 

 nearly allied to 0. limosa Ag., from which it differs in its smaller dimensions, in 

 the capitate habit and in the absence of attenuation. The terminal cell is certainly 

 a very characteristic feature ; in many of the trichomes it is prominently inflated 

 and quite devoid of contents, its membrane, however, being little if at all thickened 

 (figs. 55, 57, 58). The septa are generally completely obscured by often coarse 

 protoplasmic granules, which mostly form a dense double row on either side of 

 the septum, although in some few cases there was but a single row of granules 

 (fig. 57). 



49. Oscillatoria tenuis. 



Oscillatoria tenuis Agardh, Alg. Decades, ii. (1813), p. 2.5 ; Gromont, torn. cH., pp. 220-221, PI. VII., figs. 

 2 and 3. 



Diam. trich. = 6-7 ja. 



Hab. — Pond in eskers along shore of Western land, December 14th, 1902 ; 

 pond in eskers upon ice, half-way between Black and Brown Islands, January 3rd, 

 1903 ; pond in ice, off Black Island, McMurdo Strait, December 31st, 1902. 



