804 



XX. POTAME^. 



carpels, elongated or very short; stigmas simple {Tetrondum), or capitate {Lilcea), or 

 plumose {Triglochin), or papillose [Scheuchseria) ; ovules 2, collateral, erect, or solitary 

 and basilar, anatropous. Fbuit of distinct spreading follicles, opening by their 

 ventral suture {Scheuckzeria), or a 4-6-3-celled capsule, opening by the ventral 

 sutures of the carpels {Triglochin, Tetrondum), or indehiscent [Liloea). Seeds erect, 

 exalbuminous. Embkto straight ; radicle inferior. 



Scheuclizeria. 



PEINCIPAL GENEEA. 

 Triglochin. Tetroncium. 



Lilsea. 



Juneaginea, which are closely allied to Alismaceie, also approach NaiadeiB (see these families). 



Triglochin is a widely- dispersed genus, growing in marshes or brackish grounds of all temperate 

 regions. ScJieuchzeria grows in the turfy swamps of Europe and North America. Tetroncium belongs 

 to the Magellanic lands, and Zilaa to New Grenada and Cliili. 



XX. POTAME^, Jussieu. 



Annual or perennial plants ; rhizome sometimes with swollen joints, growing in 

 fresh, brackish or salt water. Stems knotty-jointed, usually branched, radicant. 



Potamogeton ctnspvs. 

 Flower (mag.). 



Potamogelon perfolialus. 



Ruppia 



i inflorescence (mag.). 



P. crisjms. 

 Stamen and sepal (mag.). 



