CUARACEiE. 183 



Stems 6 inches to 1 foot long ; primary branches J to 2 inches long. 

 N. mucronata has sometimes much the habit of N. flexilis, but may be 

 distinguished by its more divided branches, of which the ultimate rays 

 are often 2-celled and tipped with a small conical cell or mucro. 



I have not seen Mr. Borrer's specimens of this plant, but Messrs. 

 Groves state that it is near the var. heteromorpha, Braun [figured in 

 Bischoff, Handb. Bot. Term, und Syst. t. 57, f. 2811], and this is shown 

 by the figure they give of it, which was drawn from Mr. Borrer's 

 specimen. Var. heteromorpha is the name given to the form in 

 which the secondary whorls are contracted, and not lax like the 

 primary ones. 



Mucronate Nitella. 



SPECIES V.— N ITELLA GRACILIS. Agardh. 



Plate 1903. 



Braun, Babenh. & Stiz. Char. Europ. Exsicc. Nos. 24, 25, 57, 58, 59. 



Nordst. & Wahlst. Char. Scand. Exsicc. Nos. 15, 16, 17. 



Nitella gracilis, Agardh, Syst. Alg. p. 125. Braun, Consp. Char. Europ. p. 2 ; Schweiz. 



Char. p. 10 ; in CWm, Krypt. PL Schles. Vol. I. p. 399 ; and Pragm. Monog. Char. 



p. 58. Coss. & Germ. Fl. Envir. Par. ed. i. p. 683 ; and Atlas pi. 41, f. e ; ed. ii. 



p. 897 ; and Atlas pi. 47, f. f. Kiitz. Phyc. Germ. p. 256 ; Phyc. Gener. p. 319 ; 



Sp. Alg. p. 515 ; and Tab. Phyc. Vol. VII. p. 14, t. 34, f. i. Nordst. in Anderss. 



Bot. Notiser, 1863, p. 38. Crepin in Bull. Soc. Bot. Belg. Vol. II. p. 128. 



Wallm. in Kongl. Vet. Akad. Handl. Stockh. 1854, p. 247. Leonhardi in Brunn 



Verhandl. Vol. II. p. 170. Wahlst. Bidr. Skand. Char. p. 1 ; and Monog. Sver. 



Norg. Char. p. 19. H. & J. Groves in Journ. Bot. 1880, p. 164, t. 210, f. 15. 



Baling. Man. ed. 8, p. 469. Midler in Bull. Soc. Bot. Geneve, 1881, p. 52. Sijdow, 



Europ. Char. p. 25. 

 Chara gracilis, 8m. Engl. Bot. No. 2140. Bruzel. Obs. Char. pp. 17 and 24. Bischoffi 



Hand. Bot. Term, und Syst. t. 57, f. 2810. Beichenb. Iconog. Vol. VIII. p. 36. 



t. 793. A. Braun in Flora, 1835, Vol. I. p. 53. Ganterer, Osterr. Char. p. 10, 



t. i. f. ii. Baling, in Ann. Nat. Hist. 1850, Vol. V. p. 84. 

 C. exilis, Barlieri in Amid, Descriz. Char. p. 20, t. iii. f. vi. 



Monoecious. Bright green. Stem slender, pellucid, without cortical 

 cells or spine-cells or stipule-cells. Branchlets 4 to 7 in a whorl j 

 capillary, most of them 2 to 3 times bi- or tri- or quadrifurcate, the 

 ultimate divisions shorter than the lower, often of 2 cells, sharply 

 mucronate, those of the primary whorls rather lax and with elongated 

 segments, those of the secondary whorls similar and also lax. Nucules 

 solitary immediately below all the forks of the rays of the branchlets, 

 subglobose, 6- to 7-striate, with a very minute deciduous crown. 

 Globules solitary between the forks of the branchlets, immediately 

 above the nucules. 



