3i8 REPORT OK NEW JERSEY STATE MUSEUM. 



Family LEMNACE^. Duckweeds. 



Minute floating aquatic plants, consisting of a disc-like or 

 globular thallus, often with thread-like roots below. Growth 

 mostly by lateral branching, the branches soon separating and 

 forming new plants. Flowers rare, consisting of either a single 

 stamen or single pistil, appearing on the upper surface of the 

 thallus. The smallest flowering plants known. Apparently 

 absent from the Pine Barrens. 



Key to the Species. 



a. Frond disc-like, 2-8 mm. in diameter. 



b. Rootlets several, diameter of frond 3-8 mm. Spirodela polyrhiza, p. 318 

 bh. Rootlet single. 



c. Frond round oval, diameter 2-5 mm. Lemna minor, p. 318 



cc. Frond pointed at one end, diameter 2-3 mm. 



Lemna perptisilla, p. 318 

 aa. Frond globular, 7-1.5 mm. in diameter. WolMa columbiana, p. 319 



SPIRODELA Schleiden. 

 Spirodela polyrhiza (L.). Larger Duckweed. 



Limna polyrhiza Linnaeus, Sp. PI. 970. 1753 [Europe]. — Willis 59. — Britton 

 255. 



Floating on the water in ponds, ditches, etc. Frequent in the 

 Northern, Middle and Cape May districts. 



Middle District.— Fish House, Delair, Medford (S), Mickleton (H). 

 Cape May. — Green Creek. 



LEMNA L. 

 Lemna minor L. Smaller Duckweed. 



Lemna minor Linnaeus, Sp. PI. 970. 1753 [Europe]. — Willis 59. — Britton 254. 



Frequent in the same situations as the last and with the same 

 distribution. 



Middle District. — Farmingdale, Fish House, Delair, Blackwood (S). 

 Cape May. — Cape May. 



Lemna perpusilla Torr. 



Lemna purpusilla Torrey, Fl. N. Y. H. 245. 1843 [Pond on Staten Island]. 

 Willis 59.— Britton 254. 



Similar situations; reported only from the Northern district 

 and from one locality within our range, i. e., "Atlantic City — 



