POND-WEED TRIBE. 



647 



RUPPIA MARf-riMA (Sea Euppio). 



3. ZANNICHELLIA (Horned Pond-weed). 



1. Z. palustris (Horned Pond- weed). The only 

 British species. A submersed aquatic, with the habit 

 of Potamogeton pusillus, from which it may be well dis- 

 tinguished by its small, almost sessile, axillary flowers, 

 the stigmas of which are unevenly cup-shaped. M. 

 August, September. Perennial. 



