154 CONJUGATED. 



The above Zygnema, which Mr. Woods has so accurately 

 described, is also the variety of Z. quininum (C. spiralis), 

 referred to by me in the 10th vol. of the " Annals," p. 35. I 

 have now, however, had numerous opportunities of examin- 

 ing it in all stages of its developement, and have no doubt 

 about the propriety of separating it from that species from 

 which it is distinguished by its finer filaments, and shorter 

 cells, as well as by the manner in which the sporangia are 

 formed ; characters which are constant. 



29. ZYGNEMA ALTERNATUM Hass. 



Plate XXXIII. Fig. 3. 



Char. Filaments considerably finer than those of Z. tVoodsii. 

 Cells usually two and a half times as long as broad. 

 Sporangia oval, not producing any inflation of the re- 

 ceiving cell. 

 Hob. Cheshunt: A.H.H. 



I have seen this but once : it may possibly be but a variety 

 of the preceding species, although I can scarcely suppose that 

 it is so. 



30. ZYGNEMA ABBREVIATUM Hass. 



Plate XXXIV. Fig. 4. 



Char. Filaments about equal to those of Zygnema commune 

 in size. Cells once, or once and a half as long as broad. 

 Sporangia oval, small, not producing any inflation of the 

 cells in which they are lodged. 

 Hob. Cheshunt: A.H.H. 



This also I have only once met with. It appears distinct, 

 however. 



31. ZYGNEMA ANGULARE Hass. 



Plate XXXIV. Figs. 1, 2, 3. 



Char. Filaments at first straight, but at the period of repro- 



