Rep. Missouri Bot. Gard. 16: 102 (1905) APNI
Emergent leaves sagittate, 4.5–10 cm long, 0.2–2 cm wide; basal lobes linear to attenuate. Inflorescence with 2–4 pseudowhorls of flowers. Bracts 0.5–1.2 cm long. Pedicel of female flowers ascending, 1.5–3.5 cm long. Outer perianth lobes reflexed, 0.4–0.7 cm long; inner perianth white, nearly twice as long as outer perianth. Filaments of male flowers glabrous. Achene 2.3–3.2 mm long, 1.6–2.3 mm wide; surface unadorned or with 1 or 2 narrow wings; apex with persistent base of style (0.7–)1.0–1.5 mm long.
This native of North America has been collected only once, in 1910, from swamps on Goulburn River, near Nagambie. Unlike some other species of Sagittaria, it appears that this species has not persisted in Victoria, as there have been no records of this distinctly sagittate-leaved species in the last 100 years.
Sagittaria brevirostra has sagittate leaves similar to those of S. calycina and specimens that resemble S. sagittifolia that occur in New South Wales. However, the pedicel of the female flowers is distinctly thickened in S. calycina. The outer perianth lobes of the female flower are reflexed in S. brevirostra (appressed to the mature receptacle in S. calycina). Specimens identified as S. sagittifolia in New South Wales cannot be identified accuratley as they lack seeds (Adair et al. 2012). They are possibly unusual S. calycina records, however, the female flowers of these plants lack thickened pedicles and have reflexed outer perianth lobes. These plants can be distinguished from S. brevirostra by the purple area at the base of inner perianth lobes which is absent in S. brevirostra.
Adair, R.J.; Keener, B.R.; Kwong, R.M.; Sagliocco, J.L.; Flower, G.E. (2012). The biology of Australian weeds 60. Sagittaria platyphylla (Englemann) J.G. Smith and Sagittaria calycina Englemann, Plant Protection Quarterly 27: 47-58.