62 EQUISETACEAE 



1 8. Polypodium [Tourn.] L. 

 I . P. vulgare L. On rocks or rocky banks : Lab. and Newf . to 

 Man., south to Ga., Ala. and Mo. 



Common throughout the range, except in the pine-barrens and 

 east and south of them, there not recorded. 



MARSILEACEAE 

 i. Marsilea L. 

 I. M. quadrifolia L. Locally rare in eastern U. S. Native of 

 Asia and Europe. 



Known in our area only from Bantam Lake, Litchfield Co., and 

 North Cromwell, Middlesex Co., Conn, and from a few scattered 

 pools where it has been unquestionably introduced. Very doubt- 

 fully endemic in Am. 



SALVINIACEAE 



Leaves 12-18 mm. long, 2-ranked, on mostly simple stem?. 1. Salvinia. 



Leaves minute, closely imbricated on pinnately branching stems. 2. Azolla. 



i. Salvinia Adans. 

 1. S. natans (L.) Hoffm. Perry Co., Mo., and near Minneapolis, 

 Minn. Reported from Central N. Y. Also Europe and Asia. 



Known in our area only from near Silver Lake, S. I., N. Y., 

 where it is introduced. 



2. Azolla Lam. 

 I. A. caroliniana Willd. Floating on Stillwater: Ont. and Mass. 

 to Br. Col., south to Fla., Ariz, and Mex. Also in Trop. Am. 



Known in our area only from a small pond in Clove Valley, S. I., 

 N. Y., there introduced; and in the Morris Canal near Bloom- 

 field, N. J. 



EQUISETACEAE 



1. Equisetum L. 



Stems annual; stomata scattered. 



Stems of two kinds, the fertile appearing in early spring, before 



the sterile. 



Fertile stems simpk , soon withering; branches of sterile 



stems solid, 3-angled, their sheaths 4-toothed; silex in 



punctiform dots. 1. E. arvense. 



Fertile stems branched when old, only the apex withering. 



