39 



1. Heteranthera dubia (Jacq.) MacM. Fig. 13, Map 22 



Common in alkaline waters of western New England, rare 

 eastward. The species is highly variable in leaf width, the widest 

 leaves being slightly less than 1 cm. It is often confusedwith a few of 

 the linear-leaved species oi Potamogeton. The easiest way to separate 

 it from Potamogeton is the presence of an obscure midvein in 

 Heteranthera while in Potamogeton the midvein is distinct. Submersed 

 plants often have small inconspicuous cleistogamous flowers. Plants 

 stranded in the mud or floating in dense mats where foliage reaches 

 the surface tend to produce "showy" yellow flowers. Thieret (1971) has 

 made similar observations on H. dubia in Minnesota. Range extends 

 from Maine, southwestern Quebec, and southern Ontario west to 

 Minnesota, Idaho, and Oregon, south to Florida, Texas, Arizona, 

 California, and Mexico. 



Rare and endangered plant lists: Maine, New Hampshire 



alkalinity: mean 63.5 mg/1; range 19.5-153.0 mg/1; (38) 

 pH: mean 7.8; range 6.8-9.5; (34) 



2. Heteranthera reniformis R. and P. Fig. 14, Map 23 



Rare, along muddy shores of rivers in southeastern Connecituct, 

 the northernmost limit of its range. Range extends from southern 

 Connecticut west to eastern New York, Kentucky, southern Illinois, 

 Missouri, and Nebraska, south to Florida, Texas, and Mexico. 



Rare and endangered plant list: New England, Connecticut 



Literature Cited and 

 Selected References 



Fassett, N. C. 1937. Three aquatics from southern Maine. Rhodora 

 39: 273-274. 



Fernald, M. L. 1925. Pontederia versus Unisema. Rhodora 27: 76-81. 



Lowden, R. M. 1973. Revision of the genus Pontederia L. Rhodora 

 75: 426-487. 



Marie- Victorin, F. 1929. Les Liliflores du Quebec, Contr. Lab. Bot. 

 Univ. Montreal 14: 1-202. 



Ornduff, R. 1966. The breeding system of Pontederia cordata L. Bull. 

 Torr. Bot. Club 39: 407-416. 



Singh, V. 1962. Vascular anatomy of the flower of some species of the 

 Pontederiaceae. Proc. Indian Acad. Sci. ser. B. 56: 339-353. 



