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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN [Vol. 9, No. 2 



SYSTEMATIC TREATMENT 



Sagittaria L. Sp. PI. 993. 1753. 



Paludal or aquatic, mostly perennial, stoloniferous herbs with milky latex. 

 Leaves emersed, floating, or submerged, with sheathing, cellular petioles, the 

 emersed with distinct, often sagittate blades, the floating frequently with unlobed 

 or cordate blades, the submerged without blades (i.e. phyllodia). Plants mostly 

 monoecious, rarely dioecious. Scape erect or lax, with 1-12 mostly 3-flowered 

 whorls, each of these subtended by a whorl of 3 bracts, occasionally with branches 

 replacing the lower flower- whorls. Flowers mostly unisexual, with staminate 

 above and pistillate below, the latter occasionally with a ring of functional or 

 non-functional stamens. Pedicels ascending or divaricate, the pistillate often 

 thickened and recurved in fruit. Sepals three, herbaceous, persistent, those of 

 the staminate flowers reflexed, those of the pistillate in fruit appressed, spread- 

 ing, or reflexed. Petals three, deciduous, white or rarely pink, occasionally with 

 a purple spot at the base. Stamens whorled, mostly numerous, with linear, subu- 

 late, or dilated filaments and bilocular, nearly basifixed anthers. Carpels nu- 

 merous, distinct, 1-celled, 1-ovuled, spirally arranged in a crowded, mostly 

 spherical head on a dome-shaped receptacle; achenes flattened, winged, beaked, 

 mostly membranaceous, with erect, campylotropous seeds. 



Type: Sagittaria sagittifolia L. Sp. PI. 993. 1753. 



Key to the Subgenera and Species of Sagittaria 



Pistillate flowers with sepals appressed or spreading, their pedicels 

 recurved and thickened in fruit; a ring of functional stamens occasion- 

 ally present. Mostly tropical, occasionally warm-temperate. Subg. 1. Lophotocarpus. 

 2. Sepals closely appressed to the pistillate flowers, these often perfect. 

 Tropical except for no. 4. 

 3. Bracts more or less thickened, at least some of them appressed to 

 the scape; leaves never sagittate. 

 4. Leaf-blades typically emersed, without lobes, thickish; achenes 



narrow-winged, entire. South America. 1. S. thombijoli a . 



4. Leaf-blades floating, cordate, thin; achenes typically crenate- 



winged. Pan tropical 2. S. guyanensis. 



3. Bracts more or less membranous (if thickish then south-temperate in 

 distribution); leaves typically sagittate. 



5. Scape constricted at the whorls; achenes 4 mm or more long; pistil- 



late flowers subsessile. Amazon basin. 3. S. sprucei. 



5. Scape not constricted; achenes smaller; pistillate flowers obviously 

 stalked. Warm-temperate, New World, if tropical not in lowlands. 



4. S. montevidensis . 

 2. Sepals only loosely appressed to or spreading from the pistillate 

 flowers, these only rarely perfect. New World warm-tempeiate and 

 semi-tropical northern latitudes. 

 6. Pistillate pedicels thickened and fleshy. Semi-tropical (no. 5, 

 California). 



7. Leaves typically emersed with distinct blades; achene-beaks 

 thick- based, short. 



8. Leaves never sagittate; achenes plain. California. 5. S. sanfordii. 



8. Leaves typically sagittate; achenes tuberculate. West Indies, 



Colombia. 6. S. intermedia. 



7. Leaves submerged,. phyllodial; achene-beak filiform. Mexico. 7. S. demersa. 



6. Pistillate pedicels scarcely thickened. Atlantic coastal plain, 



United States. 8. S. subulata. 



Pistillate flowers with reflexed sepals, their pedicels typically ascend- 

 ing (at length recurved but not markedly thickened in nos. 10b and 14); 

 perfect flowers rarely present. Mostly north-temperate, occasionally ex- 

 tending to the tropics. Subg. 2. Sagittaria. 



