19 



1. Proserpinaca palustris L. Fig. 7, Map 11 



Common in the more acid waters of northern New England and 

 throughout southern New England. This heterophyllous, amphibious 

 species exhibits considerable variability in vegetative morphology. 

 Submersed leaves are divided and tend to grade toward pectinate to 

 pinnatifid to serrate as the water level drops. Serrate leaves (adult) are 

 typically associated with flowering and fruiting. However, photo- 

 period appears to influence leaf morphology in emersed plants and a 

 reversion to the juvenile leaf form (pectinate) is related to short-day 

 photoperiodicity and suggests that plants which have been referred to 

 P. intermedia fall within the range of variability of this species 

 (Davis, 1967) .Therefore, we are treating P. intermedia Mackenz. as a 

 synonym under P. palustris. Fruit variability likewise lacks disconti- 

 nuity. Thus, varieties are not recognized in this treatment. Range 

 extends from Nova Scotia west to Minnesota, south to Florida, Loui- 

 siana, eastern Oklahoma, and eastern Texas. 



alkalinity: mean 13.0 mg/1; range 2.5-100.0 mg/1; (14) 



pH: mean 6.5; range 5.4-7.3; (12) 



2. Proserpinaca pectinata Lam. Fig. 7, Map 12 



Uncommon in sandy acid ponds of eastern New England. The 

 leaves all remain finely dissected whether the plants are submersed or 

 emersed. Range extends from Nova Scotia south mainly along the 

 Coastal Plain to Florida, west to southeastern Texas. 

 Rare and endangered plant list: New Hampshire 



Literature Cited and 

 Selected References 



Aiken, S. G. 1976. Turion formation in watermilfoil, Myriophyllum 

 farwellii. Mich. Bot. 15: 99-102. 



Aiken, S. G. 1978. Pollen morphology in the genus Myriophyllum 

 (Haloragaceae). Canad. J. Bot. 56: 976-982. 



Aiken, S. G. 1979. North American species oi Myriophyllum (Halora- 

 gaceae). Ph.D. thesis. University of Minnesota. 



Aiken, S. G. 1981. An experiment relating vegetative morphology of 

 Myriophyllum alterniflorum DC. (Haloragaceae) to growth sub- 

 strate. Aquat. Bot. 10: 383-388. 



Aiken, S. G., P. R. Newroth, and L Wile. 1979. Biology of Canadian 

 Weeds. 34. Myriophyllum spicatum L Canad. J. PI. Sci. 59: 201-215. 



Aiken, S. G. and K. F. Walz. 1979. Turions oi Myriophyllum exalhes- 

 cens. Aquat. Bot. 6: 357-363. 



