NITELLA BATRACHOSPERMA. 125 



some are simple ; tertiary rays 3-7, long, sometimes 

 more than half the entire length of the branchlet, 

 occasionally again furcate. Ultimate rays uniformly 

 2-celled, lower cell tapering slightly and rounded at 

 the apex, which is but little broader than the base of 

 the ultimate cell; ultimate cell narrow c. 55-110 /* 

 long, 20-25 p, broad at the base, tapering to a sharp 

 point. Oogonia and antlieridia at the first and occa- 

 sionally at the second furcation, sometimes enveloped 

 in mucilage. Oogonia solitary c. 375-450 p. long, 

 300-350 ^ broad; spiral cells showing 8-9 convolu- 

 tions, often lengthening considerably at the apex ; 

 coronula minute, 15-25 p. high, persistent. Oospore 

 c. 225-300 p, long, 200-250 p. broad, 175 p, thick, 

 showing 6-8 broadly flanged ridges; outer membrane 

 thin, flexible, and translucent, dull-yellow-brown, at 

 first finely granulate, subsequently tending to become 

 thick and reticulate (PI. V, f. 6). Antlieridium minute 

 c. 175-200 p. in diameter. 



HABITAT. In lakes ; very rare. 



DISTRIBUTION.-- Scotland ': Outer Hebrides, loch 

 near Obbe, Isle of Harris (TF. L. Duncan, 1888). 



Ireland : Kerry, S., Caragh Lake (R. W. Scull//, 

 1889) ; Kerry, N., Lower Lake of Killarney (R. W. 

 Scully, 1890); Mayo, "\V., Lough Keel, Achill I., 

 (6r. R. B.-W., 1919) ; Donegal, W., Kindrum Lough 

 (Q. R. B.-W., 1916). 



First record: Journ. Bot. 1890. 



Outside the British Isles N. batrachosperma is 

 recorded from Sweden, Finland, Spain, France, 

 Germany and Italy; also from X. America, and 

 Australia. 



Our smallest and most delicate species, the British specimens 

 being mostly only 35 cm. high, with a stem not usually more 

 than 200 /UL thick. Larger forms occur 011 the Continent, the 

 vars. f allate and maxima (Migula) attaining the height of 10 

 15 cm. Professor Hy has made a special study of this species 

 and has given a detailed account of its variation in his paper 



