8 BEITISH CHAROPHYTA. 



with accessory ones alternating, long, acute or acuminate, 

 declining. Branchlets straight, or slightly incurved, of 

 4-5 more or less turgid segments, the ultimate segment 

 ' acute and often very short. SterUe branchlets often 

 with long turgid segments and undeveloped bract-cells. 

 Bract-cells produced at all, or all but one of the joints, 

 normally 5*, all developed, the posterior nearly as long 

 as the anterior, spreading, usually long and slender with 

 an acuminate apex, and exceeding the oogonium, 

 sometimes shorter and stouter. Bracteoles thinner and 

 shorter than the bract-cells, often shorter than the 

 oogonium, usually single, often absent. Oogonia and 

 antheridia almost always solitary, occurring at the lowest 

 1-2 nodes of the branchlets, and rarely also at then- 

 base. Oogonium produced at the base of the antheri- 

 dium, usually growing downwards, and therefore situated 

 below the antheridium, but occasionally by the side of, 

 or very rarely above it, subcylindrical-ellipsoid or ellip- 

 soid, c. 750-950 [i. long (excl. coronula), c. 400-575 y. 

 broad ; spiral-cells showing 12-15 convolutions ; coronula 

 G. 90 [I high, 200-250 [x broad, straight, the cells often 

 almost spherical. Oospore cylindrical-ellipsoid, trun- 

 cate at the apex, c. 600-750 (x long, 275-375 [i broad, 

 becoming black when ripe, showing about 11 low ridges ; 

 outer membrane thick, brittle, opaque, very dark red, 

 very finely granulated. Antheridium c. 400-500 pi in 

 diameter. 



Habitat. — In one lagoon and in a few brackish- water 

 pits close to the coast in the extreme south of England ; 

 very rare. 



Distribution. — Dorset, The Fleet, near Langton 

 Herring (W. Bowles Barrett, 1889) ; clay pit, near Ham- 

 worthy Junction {E. F. Linton, 1899) ; I. of Wight, in 

 some of the pits of the disused salterns, near Newtown, 

 where it was discovered in 1862, by A. G. More, but is 

 now apparently extinct. 



* In this and the following descriptions the number of bract-cells given is 

 that on a fertile branchlet, at the lowest node ; on the higher nodes the number 

 usually diminishes. 



