21 

 Key to Species 



1. Principal leaves forked no more than two orders (no pair of ultimate 

 segments results from more than two consecutive forkings of the 

 leaf axis) (fig. 9B); leaf segments with distinct serrations (fig. 9B), 

 the marginal teeth with wide bases (fig. 9C); fruit smooth or slightly 

 warty, with two basal spines, marginal spines lacking (fig. 9D); first 

 seedling leaves simple. 

 l.C. demersum 



1. Principal leaves often forked 3-4 orders (ultimate segment pairs 

 result from up to 3-4 consecutive forkings of the leaf axis) (fig. 9E,F); 

 leaf segments lacking distinct serrations, marginal teeth, when 

 present, with narrow base (fig. 9F); first seedling leaves at least 

 once divided. 

 2. C. echinatum 



1. Ceratophyllum demersum L. Fig. 9, Map 11 



Common in shallow quiet waters throughout New England. Fruit 

 on this and C. echinatum are uncommon, hence the vegetative charac- 

 ters are frequently used for identification. Range extends from Quebec 

 and Maine west to northern British Columbia, south throughout the 

 United States to Mexico. 



alkalinity: mean 51.6 mg/1; range 5.5-151.0 mg/1; (64) 



pH: mean 7.3; range 5.9-8.9; (62) ^ 



2. Ceratophyllum echinatum A. Gray Fig. 9, Map 12 



Locally abundant in quiet waters of southern New England. 

 Although Lowden (1978) regards this taxon as conspecific with the 

 Old World C. muricatum Cham., recent studies by Donald Les (pers. 

 comm.) have supported the recognition of the two taxa as distinct 

 species. Range extends from southwestern New Brunswick and cen- 

 tral Maine west to New York, Ohio, Michigan, Illinois, and Minnesota, 

 south to Florida, Iowa, Missouri, Arkansas, and Texas. 

 Rare and endangered plant list: Vermont 



alkalinity: mean 25.1 mg/1; range 6.0-120.0 mg/1; (7) 



pH: mean 6.8; range 5.7-7.8; (6) 



