150 CONJUGATED. 



oval, lying in cells ichich are considerably inflated for 

 their accommodation. 

 Zyynema Grevilleanum, Annals and Mag. of Xat. Hist. 

 vol. X. p. 38. 



Hah, Cheshunt and its vicinity : A. H. H. Framfield : 

 Mr. Jenner. Dolgelley : Mr. Ralfs. Turf Dyke, near 

 Ardrossan : Major Martin. 



" To this fine species I have assigned the name of Dr. 

 Greville, author of the excellent ^ Alga3 Britannica?/ as a 

 slight mark of personal respect, as well as an acknowledge- 

 ment of the eminent services rendered by that gentleman 

 to natural history." 



22. Zygnema indquale Hass. 

 Plate XXXIT. Figs. 1, 2. 



Char. Filaments of smaller diameter than those of Z. Gre- 

 villeanuw.. Cells about flve times as long as broad, and 

 enlarged on the side from ivhich the tubes of communica- 

 tion arise. Sporangia oval. 



Hah. Cheshunt : A. H. H. 



This is not a common species. I have no doubt but that it 

 is distinct. 



23. Zygnema subventricosum Hass. 



Plate XXXII. Figs. 3, 4, and 5. 



Char. Diameter of the filaments about equal to these of 

 Z. commune. Cells usually flve or six times as long as 

 broad. Sporangia oval, occasioning the cells in which they 

 are -placed to assume a ventricose form. 



Zygnema ventricosum Hassall, in Annals of Nat. Hist, 

 vol. X. pp. 38, 39. 



Hah. Cheshunt and its vicinity : A. H. H. Heathfield ; 

 in a pond near Boar's Head, Ramslye Rocks; and 



