44 



ALISMACEAE 



Petioles 0.5-1.5 dm. long: leaf-blades less than 4.5 cm. broad: whorls of the inflorescence usually soli- 

 tary: mature fruiting heads 7-8 mm. in diameter. 1. L. depauperatus. 



Petioles 1.5-4 dm. long: leaf blades over 4.5 cm. broad: whorls of the inflores- 

 cence 2-6: mature fruiting heads 10-15 mm. in diameter. 2. L. calycinus. 



1. Lophotocarpus depauperatus J. G. Smith. Leaves with petioles 0.5-1.5 dm. 

 long: scape with one flower-whorl: achenes less than 2 mm. long, slender beaked. 



On margins of ponds, Wisconsin to Illinois, Missouri and Oklahoma. Summer and fall. 



2. Lophotocarpus calycinus (Engelm.) J. G. Smith. Leaves with petioles 

 1.5-4 dm. long: scape with 2-6 flower-whorls: achenes over 2 mm. long, broad beaked. 



In swamps or ponds, South Dakota to Delaware, Alabama and New Mexico. Summer. 



5. SAGITTARIA L. 



Leaves often with basal lobes, sometimes lobeless, or mere phyllodes. Flowers 

 monoecious or dioecious, the upper ones usually staminate. Stamens mainly numer- 

 ous. Achenes numerous, in dense heads. Mainly summer and fall, or all year south- 

 ward. Arrow-head. 



not accrescent. 



5-7 



Sepals of the pistillate flowers ultimately lax or reflexed 

 Fruit-bearing pedicels reflexed or recurved. 

 Filaments glabrous. 



Scapes simple: phyllodia obtuse or abruptly pointed. 



Filaments about as long as the anthers: achenes with 



crests. 

 Filaments much longer than the anthers: achenes with 

 crenate or dentate crests. 

 Scapes branched: phyllodia slenderly attenuate. 

 Filaments pubescent. 

 Fruit-bearing pedicels ascending. 

 Leaf-blades without basal lobes. 



Pedicels of the pistillate flowers as long as those of the staminate 

 ones, or nearly so. 

 Filaments dilated, relatively short. 



Leaf-blades terete or 3-sided, often imperfectly developed. 

 Anthers longer than the filaments: achenes with several 



facial wings. 

 Anthers shorter than the filaments: achenes with 3 low 

 facial ridges. 

 Leaf-blades flat. 



Achenes oval or broadly oblong. 

 Achenes cuneate. 



Beak large, horizontal at the top of the achene-body. 

 Beak minute, borne much below the top of the 

 achene-body. 

 Inflorescence simple: lower bracts ovate, united 

 to the middle: achenes with lateral ribs or 

 wings. 

 Inflorescence widely branched: lower bracts 

 lanceolate, united at the base: achenes with- 

 out lateral ribs or wings. 

 Filarnents not dilated, slender. 

 Filaments glabrous. 



Achenes cuneate, the beak or the side above the middle 



of the body: bracts broad, well-united. 

 Achenes curved-oblong, the beak horizontal at the top 

 of the body: bracts narrow, distinct or nearly so. 

 Filaments pubescent. 



Bracts and sepals granular-papillose. 

 Bracts and sepals ribbed. 



Achenes more or less falcate, gradually beaked, the 



dorsal wing thick and even. 

 Achenes not falcate, abruptly beaked, the dorsal 

 wing usually thin and crested. 

 Pedicels of the pistillate flowers very short or nearly wanting. 

 Fruit-heads not echinate: achenes broadly winged and short- 

 beaked: anthers broadly oblong, about as long as the 

 filaments. 

 Fruit-heads echinate: achenes narrowly winged and long- 

 beaked: anthers suborbicular, shorter than the filaments. 

 Leaf-blades with basal lobes. 



Achenes minutely or inconspicuously beaked. 

 Beak borne below the top of the achene-body. 

 Beak borne at the top of the achene-body. 

 Achenes prominently long-beaked. 

 Beak horizontal. 



Inflorescence-rachis, pedicels, bracts and sepals pubescent. 

 Inflorescence-rachis, pedicels, bracts and sepals glabrous. 

 Beak erect. 



Filaments pubescent. 



Pistillate pedicels very short: sepals and bracts glabrous. 

 Pistillate pedicels elongate: sepals and bracts pubescent. 



3 undulate or slightly toothed 

 1. S. subulata. 



S. lor at a. 

 S. filiformis. 

 S. platyphylla. 



5. S. teres. 



6. S. isoetiformis. 



7. S. cycloptera. 



8. 5. Mohrii. 



9. S. graminea. 



10. 5. Chapmanii. 



11. S. papulosa. 



