ZYGNEMA. 145 



Conf. jugalis Dillw. t. 5. ; and C. nitida, t. 4. f, A. B. Z. 

 deciminum Harvey, 1. c. p. 362. ; also in Manual, p. 143. 



Hob. Cheshunt and Epping Forest: A. H. H. In a 

 pond between Ramslye Rocks and Broadwater Forest ; 

 Henfield Common; and in a pond at Hill Park, near 

 Westerham, Kent : Mr. Jenner. 



This is a very pretty species, and also very distinct, the 

 crosses described by the spires at once serving to distinguish 

 it from all others belonging to this division of the genus 

 Zygnema, Filaments frequently almost black. 



c. Spires single. 



12. ZYGNEMA QUININUM Ag. 

 Plate XXVIII. Figs. 1, 2. 



Char. Filaments of rather larger diameter than those of 

 Z. deceminum. Cells longer than broad. Spire performing 

 about three revolutions in each. Sporangia acutely oval, not 

 producing inflation of the cells in which they are lodged. 

 Conferva porticalis Miiller, Nova Comment. Petropolitana, 

 pars 3. p. 90. Conjugata porticalis Vaucher, Hist, des 

 Conf. pi. 5. fig. 1. ; Dillw. t. 3. lower figure. 

 Hab. Everywhere common throughout Britain. 



" This conjugata, already described and observed by 

 Miiller, is perhaps the most common of all those of the same 

 family ; its spires are formed of brilliant grains united by a 

 thread or a tube. Miiller compares them to porticos, since 

 in a certain state of their developement they have the form of 

 a semi-ellipse." Vaucher. The specific name of quininum 

 bestowed upon them by Agardh is intended to express as well 

 as Miiller's of porticale, which ought properly to have been 

 retained on account of its priority, the form described by 

 each turn of the spires. 



13. ZYGNEMA VARIANS Hass. 

 Plate XXIX. Figs. 1. 2, 3, 4. 



Char. Filaments of somewhat less diameter than those of 



