- 46 - 



27. Potamogeton alpinus Balbis Fig. 29, Map 29 



Common in northern Maine and northern Vermont; sporadic 

 at other locations in northern and western New England. Two 

 varieties have been described, var. subellipticus (Fern.) Ogden 

 and var. te nuifolius (Raf.) Ogden (Ogden, 1943). Plants in New 

 England have been observed with the leaf forms of both varieties 

 on the same plant. Therefore we are not recognizing these 

 varieties as distinct. Range extends from Newfoundland west to 

 Alaska, south to eastern Pennsylvania, New York, Michigan, 

 Minnesota, Colorado, Utah, and California. 



Rare and endangered plant list: New Hampshire 



alkalinity: mean 40.5 mg/1 ; range 4.0-115.0 mg/1 

 pH: mean 7.3; range 6.5-9.9 



28. Potamogeton gramineus L. Figs. 30, 31, 32, Maps 30, 31, 32 



Extremely common throughout New England. This is a 

 highly variable species that hybridizes with most broad-leaved 

 pondweeds, especially P_^ illinoensis . Such hybrids are often 

 confused with P^ gramineus var. maximus . A rare narrow-leaved 

 form with partially adnate stipules has been described from New 

 Hampshire (Hellquist, 1978). Range extends from Newfoundland 

 west to Alaska, south to New Jersey, Pennsylvania, southern 

 Indiana, Iowa, New Mexico, Arizona and California; most 

 abundant in the Northeast and in the Great Lakes region. Three 

 varieties that blend into each other have been described. Only 

 the extremes are easy to distinguish from the typical variety. 



1. Most leaves elliptic to oblanceolate, 0.2-15.0 mm 

 wide, 5-11-veined. 



2. Larger submersed leaves 5-7-veined, up to 8.0 

 mm wide. 



var . gramineus 



2. Larger submersed leaves 7-9 (-11) -veined , up 

 to 15 mm wide. 



var . maximus Morong 



1. Most leaves with sides often parallel, 1-3 mm 

 wide, 3-veined. 

 var . myr iophyllus Robbins 



alkalinity: mean 29.9 mg/1; range 2.5-123.5 mg/1 

 pH : mean 7.1; range 5.0-9.8 



29. Potamogeton illinoensis Morong Fig. 33, Map 33 



Locally abundant in hard waters of western New England. 

 Presently it is found at only two eastern Massachusetts sites. 

 This species often hybridizes with P^ gramineus . Such hybrids 

 are confused with P. gramineus var. maximus . Range extends 

 from New England west to southern Manitoba and British Columbia, 

 south to Florida, Texas, southern California, and Mexico; most 

 abundant in the Great Lakes region, eastern New York, and 

 western New England. 



