104 BRITISH CHAROPHYTA. 



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

 acuminate, or sometimes slightly mucronate. Oogonia 

 iisually 2-3 together, varying much in size, 625-900 /a 

 long, 550-750 /a broad ; spiral cells showing 8-9 con- 

 volutions, swelling considerably at the apex ; coronula 

 c. 40 /A high, deciduous. Oospore c. 500-575 /a long, 

 425-500 /A broad, 375 ju, 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 /a 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, ^Y., 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 

 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, but sometimes attaining a height of about 1 metre, some- 

 times quite small. Some of the larger and stouter forms 



