114 BRITISH CHAROPHYTA. 



IV. Wahlbergiana WALLMAN Charac. p. 26 (1853) ; Transl. p. 23 (1856) 



(= subsp. Wahlbergiana Brann & Nordstedt). 

 NORDSTEDT in Bot. Notiser, 1863, p. 37. 

 WAHLSTEDT Mon. Sver. & Norg. Charac. p. 18 (1875). 



EXSICCATA : Aresclioug 49 (133), 250, 393 (subsp. Wahlbergiana, fide 

 Wahlstedt); Billot 2994; Braun Rab. & Stiz., 17, 20, 30, 56 (Wahl- 

 bergiana) ; Fries Hb. Norm. XII. 100 ; Groves 57 ; Jack Leiner & Stiz., 

 20, 204 & b ; Mignla, Sydow & Wahlst. 32 ; Nielsen 8 (fide Wahlstedt) ; 

 Nordstedt & Wahlstedt 82, 83 (Wahlbergiana); Rabenhorst 67, 420; 

 Reichenb. 98 ; Westendorp & Wall. 1093. 



Monoecious. Stem moderately stout; internodes 

 from once to twice the length of the branchlets. Whorls 

 of usually 5-6 stoutish branchlets, the sterile and fertile 

 whorls usually not dissimilar. Branchlets once to three 

 times furcate, the sterile once or twice, the fertile 

 usually twice or three times, the primary ray being 

 about | to f the length of the whole branchlet. Rays 

 at the first furcation usually 3 or 4, at the second 2-3, 

 of which 1 or 2 is sometimes again furcate with 2-3 

 quaternary rays. Ultimate rays 2- rarely 3-celled, the 

 lower cell usually rounded or somewhat acuminate at 

 the apex, the upper very much narrower, short, conical 

 acute, thus forming a distinct mucro. Ooc/onia and 

 antheridia usually produced at each forking. Oogonia 

 solitary or geminate, attaining to a length of c. 550 

 575 /x, c. 400 p, broad; spiral cells showing 7-9 con- 

 volutions not ultimately swelling at the apex, but 

 lengthening considerably, making the oogonium ob- 

 pyriform when fully grown, at the earlier stage sub- 

 globose, breadth c. 400-450 p, ; coronula 35-45 /x high ; 

 persistent. Oospore c. 300-350 /x long, 250-300 /x, 

 broad, 200 /x thick, dark brown, showing 6-7 thin pro- 

 minent ridges; outer membrane thin, flexible and 

 translucent, light yellow-brown, reticulate (PI. V, f . 1). 

 Antheridium small, c. 275 /A in diameter. 



HABITAT. In still and running water ; rare. 



DISTRIBUTION.- -^n^a?^: Hants, N., Fleet Pond 

 (Hon. J. L. Warren, 1873) ; Sussex, W., ditch at 

 West Orinstead (W. Borrer, 1820); Middlesex, Isle- 

 worth (Dillenius about 1726) ; Berks and Oxon in two 



