1955] 



REVISION OF THE GENUS SAGITTARIA 



195 



3. Sagittaria sprucei Micheli in DC. Monogr. Phan. 3: 80. 1881. 



Perennial with horizontal rhizome. Leaves emersed, sagittate, prominently 

 veined, with widely ovate, triangular blades 3-14 x 2-11 cm, their lobes 

 4-12 x 1.5-5 cm, lanceolate-triangular, the petioles 20-60 cm long. Scapes no- 

 ticeably constricted at the nodes, 25-85 cm long, simple or branching at the 

 lowest whorl, with 4-12 whorls of flowers. Bracts connate at the base, membra- 

 nous, the linear tips to 1 cm long, occasionally obsolete, often entirely lost. 

 Pistillate flowers subsessile or on short, recurved thickened pedicels to 1.2 cm 

 long; sepals small, 0.5-0.8 x 0.7-1 cm, closely appressed to but scarcely cover- 

 ing a third of the mature receptacle; petals oblong, all white, about twice the 

 length of the sepals. Staminate flowers with short, divaricate pedicels 0.5-1.5 cm 

 long; stamens 9-12, with linear, glabrous filaments 2-3 mm long, the ovate anthers 

 only one third as long. Mature pistillate heads 1.5-2 cm in diameter; achenes 

 large, 4-6 x 2.5-4 mm, the prominent dorsal wing about 0.6 mm wide, the ventral 

 wing nearly obsolete, the faces adorned with a prominent resin duct, the laterally 

 inserted beak 2-2.5 mm long, straight or variously curved. (FIG. 2c, d.) 



Type collection: Spruce s.n,, 1855, in swamps near Barra (Manoas), Province 

 of Rio Negro, Brazil (holotype K, isotype NY); 



Distribution: Amazon Basin, South America. Collections examined from Brazil, 

 Colombia, Peru. (FIG. 2.). 



A plant of the quiet, shallow waters of lakes, streams and swamps; apparently 

 confined to the basin of the Amazon River and its tributaries. An infrequently 

 collected and little known species, probably much more common than the collec- 

 tions indicate. All specimens have sagittate, emersed leaves well above the 

 water. Micheli in his original description states that the pistillate flowers are 

 perfect; however, none of the specimens examined indicates the presence of sta- 

 mens. Sagittaria sprucei is most closely related to S. montevidensis, sharing with 

 that species the sagittate, prominently veined leaves and the typical floral 

 characteristics of subg. Lophotocarpus. It is, however, unique in the constriction 

 of the scape at the nodes, as well as in the size of the achenes and the short to 

 subsessile, pistillate pedicels. 



4. Sagittaria montevidensis Cham. & Schlecht. Linnaea 2: 156. 1827. 



Fibrous-rooted annual, or perennial with short, thick rhizome. Leaves exceed- 

 ingly variable, emersed, floating or submerged, typically emersed, prominently 

 veined and sagittate, the blades linear to widely ovate, 2-20 x0.4-25 cm, the 

 linear to ovate, divergent lobes 2-20 x 0.3-15 cm, occasionally reduced or absent, 

 the floating leaves ovate, to 2.5 x 1.5 cm, the submerged leaves reduced to phyl- 

 lodia 3-45 x 0.4-1.2 cm, occasionally with spatulate ends to 1.5 cm wide, the 

 petioles 8-70 cm long. Scape 7-75 cm long, with 2-12 whorls of flowers, simple 

 or branching from the lowest whorl. Bracts connate, 0.2-2.5 cm long, membranous 

 or occasionally thickened, the tips attenuate or reduced. Pistillate flowers with 

 thickened, recurved pedicels 1-7 cm long; sepals broadly ovate, 0.6-1.5 x 0.6-1.5 

 cm, closely appressed to the mature receptacle; petals ovate, to 2.2 cm long, 

 white or with purple marking at the base; ring of 9-12 functional stamens occa- 

 sionally present. Staminate flowers with filiform divaricate pedicels 1-4 cm long; 

 stamens 12-<», with linear or dilated, glabrous or pubescent filaments 0.7-3.5 mm 



Explanation of Figures 3-5 



FIG. 3. Distribution of S. sagitti folia, a, achene, X 3. b, bracts, X 1. c, stamen, 

 X 7. FIG. 4. Distribution of S. pygmaea. a, achene, X 3« b, bracts, X 1. c, stamen, X 7. 

 FIG. 5. Distribution of S. guyanensis. a, b, subsp. guy an en sis. a, bracts, X b, achene, 

 X 3. c, achene of subsp. lappula, X 3. 



