Potamogeton 



POTA MOGETON ACEAE 



81 



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50 



Map 89 



Potamogeton epihydrus Raf. 



'" 50 



Map 90 



Potamogeton zosterif ormis Fern. 



13. Potamogeton Richardsonii (Bennett) Rydb. Map 88. In a few of 



our northern lakes. 



Que. to Mack, and B. C, southw. to N. E., N. Y., Ind., and Nebr. 



14. Potamogeton epihydrus Raf. Map 89. Our only specimen is one 

 collected in 1936 by R. M. Tryon, Jr. It was found in State Line Creek in 

 La Porte County. It has been reported but, no doubt, all other reports 

 should be referred to other species. 



N. B., Que. to Minn., southw. to N. J., W. Va., 111., and Iowa; also on the 

 Pacific coast from Wash, to Calif. 



15. Potamogeton zosteriformis Fern. (Mem. Gray Herb. 3: 36-40. 

 1932.) {Potamogeton zosterif olius of American authors.) Map 90. Fre- 

 quent in the lakes of the lake area from which there are many reports. 

 Sterile specimens of this species closely resemble sterile specimens of 

 Heteranthera dubia from which they can be separated by the abruptly 

 acute leaf tips. Those of Heteranthera dubia have the blades gradually 

 tapering at the apex into a blunt tip. 



Que., n. Alberta to s. B. C, southw. to Va., Ohio, n. Ind., n. 111., n. Iowa, 

 Nebr., nw. Mont., and n. Calif. 



16. Potamogeton Friesii Rupr. Map 91. In a few of our northern 

 lakes. 



Southern Lab. to B. C, southw. to N. S., Conn., N. Y., Mich., Iowa, and 

 Wash. ; also in Eu. 



17. Potamogeton foliosus Raf. var. genuinus Fern. Map 92. Infrequent 

 throughout the state in creeks, small rivers, ditches, and gravel pits but 

 rarely in lakes. 



Western N. Y., Ont., Mich., Wis., s. Man. to Wash., southw. through 

 the U. S. to W. I. and Cent. Amer. 



17a. Potamogeton foliosus var. macellus Fern. (Mem. Gray Herb. 3: 

 46-51. 1932.) Map 92a. The distribution of the variety is indicated on 



