16 ARALES 



2. SPARGANIACEAE. 

 Sparganium. 39. 



1. Sparganium eurycarpum Engelm. Bur-reed. 



Common in wet places and in shallow water. Anselmo; Belmont; 

 Cherry County; Cedar County; Kearney; Lincoln; Peru;' Thedford; 

 Valentine. 



3. TYPHACEAE. 



Typha. 38. 

 1. Typha latifolia L. Common Cat-tail. 



Comm^on along streams, ditches and in wet ground. Alliance, Ansel- 

 mo; Belmont; Lincoln; Norway; Peru; Thedford; Wahoo. 



4. LEMNACEAE. 



Rootlets several. 1. Spirodela. 

 Rootlets not more than one. 



Rootlets usually present, thallus over one mm. long. 2. Lemna. 



Rootlet wanting, thallus less than one mm. long. 3. Wolffia. 



1. Spirodela. 232. 



1. Spirodela polyrhiza (L.) Schleid. Greater Duckweed. 



Common on the surface of ponds and slow streams. Anselmo; Fre- 

 mont; Linciln; Long Pine; Thedford; Valentine. 



2. Lemna. 232. 

 Duckweeds. 



Thallus with a stalk-like projection at the base. 



Stalk long, thallus 5 to 15 mm. long. 1. L. trisulca. 



Stalk short, thallus less than 5 mm. long. 2. L. perpusilla. 



Thallus not stalked. 



Thallus nearly symmetrical, green or purplish beneath. 3. L. minor. 



Thallus unsymmetrical, pale beneath. 4. L. gibba. 



1. Lemna trisulca L. 



Common in ponds throughout the state. Ashland, Cherry County; 

 Fremont; Greenwood; Harrison; Newark; Thedford. 



2. Lemna perpusilla Torr. 

 Thomas County. 



3. Lemna minor L. 



Common on the surface of ponds or slow streams. Anselmo; Banner 

 County; Cherry County; Holt County; Long Pine; Pine Ridge; Valen- 

 tine. 



4. Lemna gibba L. 



In ponds in the sand-hill regions. Kennedy; Merriman; Thomas 

 County. 



3. V\rolffia. 233. 



1. Wolffia punctata Griseb. 



Wolffia brasiliensis Weddell. 

 In ponds, rare. Bellevue; Long Pine. 



