SPARGANIACEAE 



Sparganium (Bur-reed) 



Plants of fresh water and marshes; growing from fibrous roots or 

 short rhizomes; stems and leaves erect or floating; flowers unisexual, 

 borne in globose heads, staminate heads borne above pistillate heads, 

 pistillate heads appearing bur-like; fruit obovoid or fusiform, fre- 

 quently with a slight median constriction, 1-2 seeded. 



Key to Species 



1. Stigmas 2 (fig. 3D); fruits 4-8 mm broad, truncate (flattened on end 

 except for beak) (fig. 3C). 



1 . S. eurycarpum 



1. Stigmas 1; fruits less than 4 mm broad, tapering to a beak (figs. 5C, 

 6D). 



2. Staminate head 1 (fig. 4A); fruiting heads 0.8-1.2 cm in diameter; 

 beak of fruit 0.5-1.5 mm long. 



2. S. minimum 



2. Staminate heads 2-20; fruiting heads 1.2-3.5 cm in diameter; 

 beak of fruit 1.5-6.0 mm long, 

 3. Beak of mature fruit flattened and strongly curved (fig. 5C). 



3. S. fluctuans 



3. Beak of mature fruit round, not strongly curved. 



4. Pistillate heads borne directly in axils of leaves or bracts 

 (figs. 6C, 7B). 



5. Fruiting heads 2.5-3.5 cm in diameter; stigmas 2.0-3.2 mm 



long; beak 4.5-7 mm long; body of fruit shiny (rarely dull). 



A. S. androcladum 



5. Fruiting heads 1.5-2.5 cm; stigmas 0.8-1.5 (—2) mm long; 

 beak 1.5-5.0 mm long; body of fruit dull. 



5. S. americanum 



4. Pistillate heads (at least some) borne above the axils of 

 leaves or bracts (supra-axillary) (figs. 8B, 9B). 



6. Fruit beak 0.5-2.0 mm long; stigmas 0.6-1.5 mm long; 

 fruits reddish at base; stems and leaves lax, mostly float- 

 ing (fig. 8A), up to 12 dm long. 



6. S. angustifolium. 



6. Fruit beak 2.0-4.3 mm long; stigmas 2.0-4.3 mm long; 

 fruits greenish at base; stems and leaves erect and emer- 

 gent (occasionally floating), up to 8.5 dm long. 



1 . S. chlorocarpum 



