10 



HYDROCHARITACEAE 



1. Leaves basal, long, linear and ribbon-like (fig. 5A,E) with a broad 

 lacunae band (fig. 5G). 



Vallisneria 



1. Leaves cauline, short, opposite or whorled, without a lacunae band. 

 2. Upper leaves in whorls of 4 (-6), occasionally more; leaves L2-4.0 

 cm long. 



Egeria 



2. Upper leaves in whorls of 3 (-2); leaves 0.6-L7 cm long. 



Elodea 



Vallisneria (Tapegrass, Eelgrass) 



Submersed perennial plants of freshwater; leaves basal, long and 

 ribbon-like; monoecious; pistillate flowers solitary, sessile, enclosed in 

 a tubular spathe, reaching surface by peduncle elongation; staminate 

 flowers numerous, enclosed in spathes borne on short stalks, released 

 and floating to the surface; fruit elongate, cylindrical, peduncle recoil- 

 ing after fertilization, submersing fruit. 



1. Vallisneria americana Michx. Fig. 5, Map 6 



Common in acid and alkaline waters of New England. Sterile 

 plants of Vallisneria and forms oi Sagittaria with ribbon-like leaves 

 are easily confused. Thieret (1977) notes that Vallisneria does not pro- 

 duce milky juice (characteristic in Sagittaria) and rhizomes of Vallis- 

 neria consist of only a single internode between rosettes and they lack 

 scales-leaves. Range extends from southern New Brunswick west to 

 North Dakota and Nebraska, south to Florida, Texas, New Mexico, 

 and Arizona; introduced in Washington. 



alkalinity: mean 33.5 mg/1; range 3.0-115.5 mg/1; (40) 

 pH: mean 7.4; range 5.8-10.2; (38) 



Egeria (Waterweed) 



Submersed or floating perennial plant of freshwater; leaves sessile 

 in whorls or 4 (-6) along the terete stem; staminate flowers in spathes, 

 borne in upper leaf axils, raised to the surface of the water on a thread- 

 like hypanthium; pistillate plants unknown in New England. 



