104 BEITISH CHAROPHYTA. 



secondary; secondary rays 2-3 (or single), 1-celled, 

 acuminate, or sometimes slightly mucronate. Oogonia 

 usually 2-3 together, varying much in size, 625-900 JJL 

 long, 550-750 p. broad; spiral cells showing 8-9 con- 

 volutions, swelling considerably at the apex ; coronula 

 c. 40 JJL high, deciduous. Oospore c. 500-575 ^ long, 

 425-500 JJL broad, 375 /x thick, dark reddish brown to 

 black, showing 5-7 stout prominent ridges which 

 broaden into flanges at the apex ; outer membrane 

 thick and semi-rigid,, translucent or semi-opaque, 

 strong red-brown to burnt-sienna, smooth or scabrous 

 with wart-like protuberances (PI. IV, f . 4). Antheridium 

 usually c. 500-625 /x in diameter. 



HABITAT. In ponds and lakes, rarely in running 

 water; not uncommon. 



DISTRIBUTION. England: Cornwall, W., Hants, S., 

 Sussex, W. & E., Kent, W., Surrey, Essex, S. & N., 

 Herts, Middlesex, Bucks, Suffolk, E., Norfolk, W., 

 Cambs., Hereford, Worcester, Warwick, Staffs, Salop, 

 Notts, Lanes, S., Yorks, N.E., S.W., N.W., North- 

 umberland, S., Westmoreland. 



Wales : Anglesey. 



Scotland : Dumfries, Kirkcudbright, Ayrshire, Stir- 

 ling, Perth, W., M., E., Westerness, Dumbarton. 



Ireland : Kerry, S., N., Cork, W., Longford, Ros- 

 common, Mayo, E., Leitrim, Cavan, Monaghan, 

 Fermanagh, Donegal, W., Armagh. 



Channel Islands : Jersey. 



First record : doubtful, owing to confusion with 

 N. opaca. 



Outside the British Isles N. flexilis is recorded from 



t' 



Norway, Sweden, Denmark, Spain, France, Belgium, 

 Holland, Germany, Switzerland, Austria, Hungary, 

 Italy, Roumania, and Russia ; also from Asia (Kam- 

 chatka and Japan) and N. & S. America. 



Very variable in stature, usually rather above the medium 

 size, bub sometimes attaining a height'of about 1 metre, some- 

 times quite small. Some of the larger and stouter forms 



