A GUIDE AND KEY TO AQUATIC PLANTS 113 



2. S. nigra Marsh. Black Willow — The common swamp willow 

 over all of our territory. It is often found in situations also favored 

 by Anopheles quadrimaculatus . 



3. S. harbisonii Schneider — Swamps in our territory from North 

 Carolina south to Florida. Apparently has been most frequently 

 collected from along rivers. It has been suspected of being a hybrid 

 between the preceding and following species. 



4. S. Icngipes Shuttle w. — Swamps and along streams mostly in the 

 Coastal Plain. Its range embraces/all of our Coastal Plain territory. 

 S. amphibia Small, described from lakes and swamps in peninsular 

 Florida, should be referred to this species. 



BETULACEAE Birch family 



1. Betula [Tourn.] L. 



B. nigra L. River Birch — Swamps of streams over all of our 

 range. Unmistakable because of its reddish, papery bark. 



2. Alnus [Tourn.] L. 



A. sirrulaia WiUd. Alder — Swamps along branches, creeks and 

 rivers in various provinces, range covers all of our territory. This 

 species is commonly referred to as Alnus rugosa (Du Roi) Spreng. 



URTICACEAE Nettle family 

 1. Boehmeria Jacq. 



1. Leaf-blades leathery, finely toothed; petioles much 1. B. drummondiana. 



shorter than the blades. 

 1. Leaf-blades thin, coarsely toothed; petioles as long as 2. B. cylindrica. 



the blades or only slightly shorter. 



1. B. drummondiana Wedd. Bog-hemp — Swamps in various prov- 

 inces, range includes all of our territory. 



2. B. cylindrica (L.) WUld. — Distribution in our territory about 

 the same as the preceding, but apparently more common. 



ULMACEAE Elm family 



1. Planera J. F. Gmel. 



P. aquaiica (Walt.) J. F. Gmel. Water Elm— Swamps along rivers, 

 range covers most of our Coastal Plain and Mississippi Valley terri- 

 tory. 



POLYGONACEAE Buckwheat family 



1. Rumex L. 



1. Leaf-blades short and broad, rounded or cordate at \. R. fascicularis. 



base; sepal-wings toothed. 

 1. Leaf-blades narrow and elongate, narrowed to the base; 2. R. verticillatus. 



sepal wings undulate. 



