134 BRITISH CHAROPHYTA. 



Monoecious. Stem very stout, often solitary, much 

 branched. Sterile whorls of about 6-20, simple 3-5- 

 celled, often very unequal branchlets, the cells diminish- 

 ing gradually in length and thickness towards the 

 apex, apical cell rather bluntly conical. Fertile whorls 

 usually in large densely crowded heads. Branchlets 

 once or twice divided, with usually 3 lateral rays and 

 one central ray, which is either elongated or again 

 divided with a central elongated ray. Ultimate rays 3- 

 5-celled, the cells usually much diminishing in length 

 and breadth towards the apex ; ultimate cell conical, 

 acute or acuminate, sometimes rather blunt. Oogonia 

 and antheridia at the nodes of the branchlets and at 

 the base of the whorl. Oogonia ellipsoid-biconical, 

 c. 500-560jLt long, 400-450 /A thick; spiral-cells show- 

 ing 1 1-12 convolutions; coronula prominent, persistent, 

 c. 50 JJL high, 65 //, broad, the cells of the upper tier 

 much the longer. Oospore amber to dull brown, globose- 

 ellipsoid, 330-400 IJL long, 250-330 /x thick, showing 

 about 9 very thin prominent often winged ridges ; 

 outer membrane very thin and flexible, light yellow and 

 translucent, undecorated. Antheridia usually sessile, 

 c. 300 ju, in diameter. 



HABITAT.- -Rivers, canals, and ditches, usually in 

 rather shallow, slowly-flowing water ; rare. 



DISTRIBUTION.- -England : Sussex, W., Henfield (W. 

 Bower, 1827), Amberley (T. Hilton), South Stoke 

 (J. G.) ; Sussex, E., near Eastbourne (H. T. Mennell) ; 

 Berks, R. Isis, near Oxford (G. C. Druce) ; Oxon, Kid- 

 lington (G. E. B.-W.) ; Norfolk, E., near Beccles 

 (G. R. B.-W.), Martham (G. E. Salmon); Norfolk, 

 W., near Brandon Creek (G. R. B.-W.); Cambs, Ely 

 (G. R. B.-W.), Ben wick (A. Fryer], Stretham Ferry 

 (G. R. B.-W.); Hunts, Ramsey St. Mary (A. Fryer), 

 Stirtloe (E. F. Linton) ; Northants, Rockingham 

 (T. B. Blow), Yelvertoft (H. N. Diwn) ; Lines, S., 

 Deeping Fen (W. H. Beeby) ; Lanes, "W., canal 

 between Lancaster and Preston, at Cabus and Brock, 

 near Garstang, etc. (A. Wilson and J. A. Wheldoii). 



