1955] 



REVISION OF THE GENUS SAGITTARIA 



207 



Distribution: Southeastern Canada and Northeastern United States; Quebec 

 and Ontario south to Virginia, Kentucky and Missouri, west to Nebraska. In fresh 

 to brackish, tidal waters, more commonly in the inland, calcareous waters of 

 lakes and streams. The species has been reported as introduced and established 

 in Europe; however, available European collections ascribed to this species 

 seem to be a short-pediceled, deep-water form of S. sagittifolia L. Collections 

 examined from Quebec, and Ontario in Canada and from Connecticut, Delaware, 

 Illinois, Indiana, Iowa, Kentucky, Maine, Massachusetts, Michigan, Minnesota, 

 Missouri, Nebraska, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, 

 Tennessee, Vermont, Virginia, Wisconsin in the United States. (FIG. 13.) 



Leaf-shape and the length of both leaf and scape are profoundly modified by 

 the habitat. Some plants of deep, slow-moving streams have elongated scapes to 

 "many meters long" (Fernald 1950, p. 89), while some plants stranded on mud 

 flats reach full maturity with a leaf and petiole less than 20 cm long. The occur- 

 rence of linear lobes on the emersed blades seems quite haphazard, but they are 

 common only on ovate or elliptical leaves. 



S, rigida is very closely related to S. graminea and apparently hybridizes with 

 that plant. Both species occur together and the absence of large numbers of in- 

 termediates suggests that the hybrids are more or less sterile. Experimental work 

 is needed to substantiate these observations. The large achenes with the stoutish, 

 recurved, and elongate beaks, the sessile pistillate flowers, and the bending of 

 the scape at the lowest whorl are all distinctive. The presence of pubescent 

 filaments, reflexed sepals on mature pistillate heads, and commonly non-sagittate 

 leaves is shared with 5". lancifolia as well as S. graminea. The large synonymy, 

 most of it on a subspecific level, has resulted solely from the plastic vegetative 

 characteristics. 



10. Sagittaria graminea Michx. Fl. Bor.-Am. 2: 190. 1803. 



Annual, or perennial with runners and corms and/or horizontal rhizomes. 

 Leaves emersed or submerged, the emersed blades linear to ovate, 1.5 x 0.5-10 

 cm, rarely with basal lobes, the submerged leaves modified into strap-shaped or 

 spongy terete phyllodia to 50 cm long and to 2.5 cm wide, the petioles 2-55 cm 

 long. Scapes 5-120 cm long, simple, with 2-12 whorls of flowers, or rarely branch- 

 ing from the lower whorls. Bracts scarcely to fully connate, the free ends 0.2-1.5 

 cm long, occasionally obsolete. Pistillate flowers with ascending pedicels 0.5-6.5 

 cm long (in one variety the pedicels recurved and somewhat thickened); sepals 

 0.3-0.6(-0.8) cm long, reflexed at maturity; petals white or pink, ca. twice as 

 long as the sepals. Staminate flowers with 12-°° stamens, the dilated pubescent 

 filaments 0.4-1.5 mm long, the oblong anthers 0.6-1.7 mm long. Mature receptacle 



0. 5-1.5 cm in diameter; achenes oblong to obovate, 1.2-3x0.8-1.8 mm, the 

 dorsal wings 0.15-0.6 mm wide, the ventral wings only half as wide, the faces 

 adorned with 1-3 wings, these occasionally crenate or absent, the obliquely 

 inserted beak 0.1-0.4 mm long, occasionally longer or obsolete. 



1. Pistillate pedicels recurved, the subulate beak of the mature achene 0.3 



mm. or more long; south-central and Gulf States. 10b. var. platypbylla. 



1. Pistillate pedicels ascending, if recurved the achene beak less than 0.3 

 mm. 



2. Scapes branching at the lowest whorl; bracts scarcely connate, the 



free ends linear, elongate; Alabama, Florida, Georgia. 10f. var. chapmani. 



2. Scapes simple; bracts moderately to fully connate, the free ends triangu- 

 lar, obtuse, or obsolete. 

 3. Submerged leaves modified into spongy terete phyllodia; bracts fully 

 connate, achene facial wings crenate; in acid water, coastal Massa- 

 chusetts, Long Island, New Jersey. 10c. var. teres 



