11 



that are always divided, or the production of the club-shaped winter 

 buds which are formed along the stem during the late summer. 

 Variety pectinatum Wallr. has long been applied to the New England 

 plants, but Aiken (1979, 1981) documents great plasticity in this 

 species and does not recognize this or any of the other varieties 

 described for this species in North America. Range extends from 

 Newfoundland west to Alaska, south to Nova Scotia, Connecticut, 

 Delaware, Maryland, the Great Lakes States, northeastern Texas, 

 Utah, and California. 



alkalinity: mean 18.0 mg/1; range 5,0-39.0 mg/1; (11) 



pH: mean 6.9; range 6.5-7.8; (11) 



7. Myriophylum heterophyllum Michx. Fig. 5, Map 8 



Locally abundant and aggressive in ponds, lakes, and streams in 

 New England. Populations of this taxon have recently become estab- 

 lished in northern New England in the Sebago Lake region of Maine 

 region and Lake Winnipesaukee, New Hampshire. The greatest con- 

 centrations of this plant are in southern Worcester County, Massa- 

 chusetts where it is well established in most waters. The populations 

 are so dense that boating, fishing, and swimming are hindered in 

 these waters. To the west of New England this species is typically 

 found in alkaline waters while in New England it has been restricted 

 to waters of low alkalinity. A small terrestrial form is often formed 

 when stranded on shore as the water level drops. Care must be taken 

 to avoid confusion of this form with M. pinnatum or terrestrial growth 

 forms of M. spicatum or M. verticillatum. Range extends from 

 southwestern Quebec, southern Maine, and central New Hampshire 

 west to Ontario, Michigan, and South Dakota, south to Florida, Okla- 

 homa, Texas, and New Mexico. 



alkaHnity: mean 12.5 mg/1; range 3.0-33.0 mg/1; (29) 



pH: mean 6.5; range 6.2-8.9; (25) 



8. Myriophyllum spicatum L. Fig. 6, Map 9 



Locally abundant and aggressive in alkaline waters of western 

 Vermont and Massachusetts, widely scattered elsewhere. This Eura- 

 sian species has long been aggressive south of New England. The 

 earliest record in New England dates to 1965 in Lake Champlain and 

 has become a problem in the Lake Champlain Valley of Vermont and 

 the Housatonic River Valley of Massachusetts. Weed irradication 

 programs have been instituted by many towns to rid lakes of this 

 weed. Three eastern New England localities have recently been dis- 

 covered: East Thompson, Connecticut, Framingham and Canton, 

 Massachusetts. These localities of low alkalinity are noteworthy as 

 they may indicate future problems with this species in the acidic 

 eastern waters. Range extends from Quebec and New England west 



