804 



XX. POTAME^S. 



carpels, elongated or very short; stigmas simple (Tetroncium), or capitate (Lilcea), or 

 plumose (Triglochin), or papillose (Scheuchzeria) ; ovules 2, collateral, erect, or solitary 

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

 ventral suture (Scheuchzeria), or a 4-6-3-celled capsule, opening by the ventral 

 sutures of the carpels (Triglochin, Tetroncium) , or indehiscent (Lilcea). SEEDS erect, 

 exalbuminous. EMBRYO straight ; radicle inferior. 



Scheuchzeria. 



PRINCIPAL GENERA. 

 Triglochin. Tetroncium. 



Libra. 



Juncaginete, which are closely allied to Alismacea, also approach Nuiadete (see tliese families). 



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

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

 to the Magellanic lands, and Lilaa to New Grenada and Chili. 



XX. POTAME^E, Jussieu. 



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

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



Potamogeton crisput. 

 Flower (mug.). 



Potamogrton perfoliatut. 



Rvppia 

 5 inflorescence (mag.). 



P. crisput. 

 Stamen and sepal (mag.). 



