ZYGNEMA. 149 



19. ZYGNEMA FLAVESCENS Hass. 

 Plate XXX. Figs. 9, 10. 



Char. Filaments of less diameter than those of Z. catenat- 

 forme. Cells usually four times as long as broad, and 

 slightly inflated for the accommodation of the sporangia, 

 which are oval. 



Hob. Hertford Heath ; High Beech, Essex : A. H. H. 

 Several places in Sussex and Kent : Mr. Jenner. 



The only species with which this could be confounded are 

 Z. catenaforme and Z. parvum, between which it is interme- 

 diate. It seems to prefer, like several other species of the 

 genus, the boggy pools of heaths, &c., to roadside ponds and 

 ditches. 



20. ZYGNEMA PARVUM Hass. 

 Plate XXX. Figs. 7, 8. 



Char. Filaments more slender than those of the preceding 

 species. Cells rather more tlian four times as long as 

 broad. Sporangia oval, generally producing a slight in- 

 flation of the cells in which they are formed. 



Zygnema parvum Hassall, in Ann. Nat. Hist. vol. x. p. 41. 



Hob. Cheshunt : A. H. H. In a pond between Ramslye 

 Rocks and Broadwater Forest : Mr. Jenner. 



This is one of the smallest species of the genus ; it is not 

 uncommon. 



** Extremities of cells inverted. 



21. ZYGNEMA GREVILLEANUM Hass. 

 Plate XXXI. Figs. 1, 2. 



Char. Filaments of rather less diameter than those of Z. 

 curvatum. Cells usually six or seven times as long as 

 broad, round the interior of each of which winds generally 

 one and sometimes two spiral threads. Sporangia broadly 



