POTAMOGETOXACEAE 7 



very variable species and has been divided into several forms by J. G. 

 Smith. Cody; Kearney; Lincoln; Long Pine; Minden; Thedford; 



2. Sagittaria arifolia Nutt. 



In the sand-hill region. Mullen; Wood Lake. 



3. Sagittaria cuneata Sheldon. 



(Sometimes included in Sagittaria arifolia Xutt.) 



In shallow water in the western part of the state. Cherry County; 



Thedford. 



4. Sagittaria longiloba Engelm. 

 Near Minden. 



5. Sagittaria rigida Pursh. 

 Sagittaria hetercplnyila Pursh 



In wet places and shallovr water over most of the state. Ewing; 

 Greenv/ood; Kennedy; Lincoln; Xeligh. 



6. Sagittaria graminea 3>Iichx. 



In muddy places and snallov.' Avater in the eastern part of the state. 

 Holt Ccunty; Lincoln; Mead; Minden. 



4. Alisma. 54. 

 1. Alisma plantago-aquatica L. Water-plantain. 



Common in mud or shallow water over most of the state. Alliance; 

 Anselmo; Callaway; Cherry County; Hom.esville; Newark; Peru; 

 Plainview; Wood Lake; Valentine. 



2. SCHEUCHZERIACEAE. 

 Triglochin. 52. 



1. Triglochin maritima L. Arrow-grass. 



In marshes in various places in the state. Alliance; Burwell; Newark; 

 Sand bars of the Niobrara; Thedford. 



3. POTAIVIOGETONACEAE. 



Flowers perfect, usually on elongated peduncles. 



Perianth segments 4; fruiting peduncles straight. 1. Potamogeton. 

 Perianth wanting; fruiting peduncle coiled. 2. Ruppia. 



Flowers monoecious, flower clusters sessile or short peduncled. 



3. Zannichsllia. 

 1. Potamogeton. 41. 



Pondweeds. 



With both floating and submerged leaves. 



Stipules axillary and free from the leaves. 



Submerged leaves bladeless, about 2 mm. wide. L P. natans. 



Subm.erged leaves with proper blades. 



Upper submerged leaves much broader and shorter than the 



lower. 2. P. amphifolius. 



Upper submerged leaves not very different from the lower. 



Floating leaves gradually narrowed into short petioles, foliage 



and spikes reddish. 3. P. alpinus. 



Floating leaves abruptly narrowed into long petioles. 



Floating leaves pointed at the base; fruit distinctly 3-keeled, 

 the middle keel often winged. 4. P. lonchitis. 



Floating leaves rounded or cordate at the base, fruit indis- 

 tinctly keeled. 5. P. heterophyllus. 



