ZYGNEMA. 141 



Hassall, in Annals of Nat. Hist. vol. xi. p. 432. 



Hah, Clieshunt, very rare : A. H. H. Withyliam : Mj\ 

 Jenner. 



The only species with which this can possibly be confounded 

 is Z. orhiculare, from which it may be readily distinguished by 

 the fewer number and serrated appearance of the spires, the 

 larger size of the granules, and the form of the sporangia, 

 which in Z. orhiculare are nearly spherical, and compressed, 

 while in Z. serratum they are broadly ovate. The filaments 

 do indeed resemble very closely in character those of Z. niti- 

 dum, Avith which, however, there is but little danger of con- 

 founding it, that species being altogether a much smaller plant. 

 It is very rare. 



5. Zygnema nitidum Ag. 



Plate XXII. Figs. 1, 2. 



Char. Filaments o/* ??z?^c/i less diameter than those of Z. serra- 

 tum. Cells usually rather more than tivice as long as broad. 

 Spires generally four in number. Granules large. Spo- 

 rangia acutely ovate. 



Conferva jugalis Mliller, Flora Danica. Conjugata princeps 

 Yaucher, Hist, des Conf. d'Eau douce, p. 64. pi. iv. fig. 1 . 

 F. nitidum Harv. in Manual, p. 143.; Agardh's Systema. 

 Conf. nitidum Dillwyn, British Confervas, pi. iv. f. c. ; 

 Eng. Bot. t. 1656, in part. 



Hab. Every where common throughout Great Britain \:^^^^^ 

 and Ireland. ^// . 



This species is one of the best marked as well as most Jhur^ 

 beautiful of the tribe. Numerous other Zygnemata have ^ 



however doubtless been associated with it under the same ^ " 



Yaucher has the following observation upon it : — " Inde- ^'^^^^^ 

 pendently of its size, it is distinguished from all others by a J^A 

 coarser touch, a more shining appearance of tubes almost crisp, / 



and by its constant habit of raising its extremities out of 

 the water whenever it is immersed in the liquid." 



