NITBLLA BATRAOHOSPBEMA. 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 /i 

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

 point. Oogonia and antheridia at the first and occa- 

 sionally at the second furcation, sometimes enveloped 

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

 300-350 ju, broad; spiral cells showing 8-9 convolu- 

 tions, often lengthening considerably at the apex ; 

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

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

 showing 6-8 broadly flanged ridges; outer inemhrane 

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

 first finely granulate, subsequently tending to become 

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

 c. 175-200 ju, in diameter. 



Habitat. — In lakes ; very rare. 



Distribution. — Scotland: Outer Hebrides, loch 

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



Ireland: Kerry, S., Caragh Lake (i?. W. Scidh/, 

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

 Scully, 1890); Mayo, ^Y., Lough Keel, Achill I., 

 (G. B. B.-W., 1919); Donegal, W., Kindrum Lough 

 {G. B. B.-W., 1916). 



First record: Journ. Bot. 1890. 



Outside, the British Isles N. hatrachosperma is 

 recorded from Sweden, Finland, Spain, France, 

 Grermany and Italy; also from N. America, and 

 Australia. 



Our smallest and most delicate species, tlie British specimens 

 being mostly only 3-5 cm.*liigh, with a stem not usually more 

 than 200 jx thick. Larger forms occur on the Continent, the 

 v&rs. fallax 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 



