ZYGNEMA. 149 



19. Zygnema flavescens Hass. 

 Plate XXX. Figs. 9, 10. 



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

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

 slightly inflated for the accommodation of the sporangia, 

 which are oval. 

 Hah. Hertford Heath; High Beech, Essex: A.H.Il. 

 Several places in Sussex and I'il^cnt : Mr. Jenner. 



The only species with which this could be confounded are 

 Z. catcnaforme 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 jjreceding 

 sjMcics. Cells rather more than four times as long as 

 hroad. Sporangia oval, generally producing a slight in- 

 flation of the cells in which they are foryned. 



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



Hah. 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 CQ\h 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 



hroad, round the interior of each of n-hich jcinds generally 



one and sometimes ttco spiral threads. Sporangia hroadly 



