180 ENGLISH BOTANY. 



no traces of mucilage, so characteristic of N. syncarpa, are visible on 

 the globules and nucules, and the spiral ridges on the nucleus of the 

 nucules are less prominent and acute than in N. opaca, and more so than 

 in N. syncarpa, though no doubt this is a variable character, and one 

 which Messrs. Grroves seem to have misunderstood, as they describe 

 the nucules (under N. capitata) as having " sharp prominent cells," 

 but the spiral cells of the nucules are not more prominent in N. capitata 

 than in N. syncarpa, and are not sharp, but rounded as in other 

 Characese ; the terms oxygyra, pachygyra, &c. used by A. Braun, 

 refer to the ridges on the nucleus between the spiral cells, which 

 correspond to the striae on the surface of the nucule, and are not 

 cells, but merely thickened portions of cell-walls. Of the specimens 

 at Kew referred by Braun to N. capitata, the Llyn Idwel plant 

 (C. gracilis, Wilson in Hook. Bot. Miscell. vol. i. p. 336 ; not of Sm.) 

 has traces of mucilage, and seems rather to belong to N. syncarpa, as 

 the nucleus of the nucule is broader, and the ridges on it are not 

 nearly so prominent and sharp as in typical N. capitata ; the Kent 

 specimen has no mucilage, and is simply the ordinary N. opaca, 

 which is doubtless but a sexual state of N. flexilis, for taking the 

 whole of the forms of N. flexilis and N. opaca there is nothing to 

 distinguish the two but sex, which is not a specific character, and 

 N. flexilis may be regarded as a polygamous species, with male, 

 female, and hermaphrodite plants. The Killarney specimens in size 

 and general appearance resemble the Llyn Idwel plant, but there are 

 no traces of mucilage on them, and except in being smaller are not 

 distinguishable from some specimens collected at Lyndhurst, and 

 distributed by Messrs. Groves as N. opaca (No. 86). N. opaca var. 

 attenuata described by Messrs. Grroves in Jour. Bot. 1881, p. 356, is 

 a striking form found at Hythe, S. Hants, with long and very slender 

 branchlets, but still is evidently only a slender state of their 

 Lyndhurst plant, and except that there is no mucilage on the globules 

 and nucules, it is identical with N. syncarpa of Nordstedt and 

 Wahlsted's Char. Scand. Exsicc. No. 2 (a form well figured in Reichen- 

 bach's Iconographia, vol. viii. pi. 798), which fact would seem to imply 

 that the presence or absence of mucilage is of doubtful value as a 

 specific character. — N. E. B.] 



Twin-fruited Nitella. 



SPECIES III.-N I TEL LA TRANSLUCENS. Agardh. 



Plate 1901. 



Braun, Babenh. & Stiz. Char. Europ. Exsicc. No. 19. 

 Nordst. & Wahlst. Char. Scand. Exsicc. No. 81. 



Nitella translucens, Agardh, Syst. Alg. p. 124. A. Braun, Consp. Char. Europ. p. 2 ; 

 and Fragm. Monog. Char. p. 49. Coss. & Germ. Fl. Envir. Par. ed. i. p. 682 ; 



