12 ZANICHELLIACEAE. 



4. Sparganium minimum Fries. In ponds and streams from N. B. to 

 Alaska, N. Y. and Utah. Grand Lake; Estes Park. 



Order 10. NAIADALES. 



Gynoecium of distinct carpels ; stigmas disk-like or cup-like. 



Fam. 13. ZANICHELLIACEAE. 

 Gynoecium of united carpels ; stigmas 2-4, slender. 



Fam. 14. NAIADACEAE. 



Family 13. ZANICHELLIACEAE Dumort. POND-WEED FAMILY. 



Flowers perfect in peduncled spikes ; ovaries sessile ; stamens 4 ; connective ap- 

 pendaged. i. POTAMOGETON. 



Flowers monoecious, axillary ; anthers i ; connective not appendaged. 



2. ZANICHELLIA. 



i. POTAMOGETON L. POND-WEED. 



With both floating and submerged leaves. 



Submerged leaves bladeless. i. P. natans. 



Submerged leaves with proper blade. 

 Submerged leaf-blades lanceolate. 



Submerged leaves all petioled. 2. P. lonchites. 



Submerged leaves sessile or the uppermost short-petioled. 



Peduncles of the same thickness as the stem. 3. P. alpinus. 



Peduncles thicker than the stem. 4. P. Zisii. 



Submerged leaves linear. 5. P. heterophylhis. 



With submerged leaves only. 



Leaves with broad blades, lanceolate or oval, many-nerved. 



Leaves short-petioled or sessile, not clasping. 6. P. lucens. 



Leaves clasping. 7. P. Richardsonii. 



Leaves narrowly linear or capillary. 

 Stipules free from the leaves. 



Glands at the base of the leaves absent. 8. P. foliosus. 



Glands at the base of the leaves present. 9. P. pusillus. 



Stipules adnate to the base of the leaves. 

 Stigma broad, sessile. 



Leaves filiform, J4~/^ mm. wide; stipular sheath 3-8 mm. long. 



10. P. filiformis. 

 Leaves about i mm. wide ; stipular sheath 1-2 cm. long. 



11. P. interior. 

 Stigma capitate; style evident. 12. P. pectinatus. 



1. Potamogeton natans L. In lakes and ponds from N. S. to Alaska, Fla. 

 and Calif.; also Mex., Europe and Asia. Alt. 4000-8000 ft Rio Grande, 

 Alamosa; Lee's Lake, Ft. Collins; Laramie River near state line. 



2. Potamogeton lonchites Tuckerm. In ponds and slow streams from N. B. 

 to Wash., Fla. and Calif. Alt. 4000-8000 ft. Alamosa. 



3. Potamogeton alpinus Balbis. (P. rufescens Schrad.) In ponds from 

 N. S. to Alaska, N. ]. and Calif. Alt. 8000-11,500 ft Georgetown ; Tomichi 

 River; Seven Lakes; Trapper's Lake. 



