1955] 



REVISION OF THE GENUS SAGITTARIA 



221 



eluding the southern Appalachian Mountains, and in all semitropical and tropical 

 latitudes. Probably not indigenous to the West Indies but introduced there as well 

 as in the Hawaiian Islands. The most common and wide-spread New World species, 

 found in extremely diverse aquatic habitats throughout its range. Collections ex- 

 amined from North America: Canada (British Columbia, New Brunswick, Nova 

 Scotia, Ontario, Prince Edward Island, Quebec, Saskatchewan); United States (all 

 states except Mississippi, North Carolina, and Tennessee, where in all probability 

 it does exist, and Montana, Nevada, New Mexico, Utah, and Wyoming); Mexico 

 (Durango, Michoacan, Puebla, Vera Cruz); Central America (Costa Rica, Honduras, 

 Nicaragua); West Indies (Puerto Rico). South America (Colombia, Ecuador, Vene- 

 zuela). Hawaii. (FIG. 17.) 



15b. Sagittaria latifolia var. pubescens (Muhl.) J.G.Sm Mem. Torrey Club 5: 25. 

 1894. 



Sagittaria pubescens Muhl. Cat. 86. 1813. 



Sagittaria sagittifolia var. pubescens (Muhl.) Torr. Comp. 356. 1826. 



Sagittaria variabilis var. pubescens (Muhl.) Engelm. in Gray, Man. Bot. ed. 5. 493. 

 1867. 



Plant sparsely stellate-pubescent throughout, the bracts and sepals sparsely 

 to densely pubescent. Leaves emersed, sagittate, the mostly obtuse blades ovate- 

 triangular. Achene beak 1 mm or more long. (FIG. 16a, b.) 



Type collection: Muhlenberg s.n,, Pennsylvania (holotype not seen, presumbaly 

 Berlin). No other pubescent or papillose Sagittaria is present in Pennsylvania; 

 therefore the identity of Muhlenberg's plant is reasonably certain. 



Distribution: Pennsylvania and Ohio, south to Florida and Alabama, west to 

 Texas. In diverse aquatic habitats; replacing var. latifolia to a large extent, espe- 

 cially in the mountains; sporadic west of the Mississippi River and along the 

 Gulf Coast. Collections examined from Alabama, Delaware, District of Columbia, 

 .Florida, Georgia, Maryland, North Carolina, Ohio, Pennsylvania, South Carolina, 

 Tennessee, Texas, Virginia, West Virginia. (FIG. 16.) 



The common widespread New World Sagittaria characterized by typically 

 sagittate, emersed leaves, which assume a bewildering number of ecological vari- 

 ations, which in turn have given rise to wide synonymy. Except for var. pubescens, 

 which has a few fixed differences and a correlated distribution, none of the other 

 taxa previously proposed can be justified. Differences that seem fixed in one 

 locality vary tremendously in another; key characteristics will occasionally differ 

 on plants o c the same clone or on the same plant at different times of the year. 

 Certain characteristics, however, which safely serve to distinguish the species, 

 remain reasonably static, including the boat-shaped bracts and the large achene s 

 with laterally inserted beaks of various lengths. 



Sagittaria latifolia is closely related to 5. cuneata and 5. engelmanniana, 

 sharing with these species a common range, typically sagittate, emersed leaves 

 and glabrous filaments. There is probably some hybridization between 5. latifolia 

 and these species, since occasional intermediates exist. The absence of large 

 numbers of intermediates, except as discussed below, suggests that these species 

 do not hybridize readily. West of the Mississippi River, where the ranges of 5. 

 latifolia and S. engelmanniana subsp. brevirostra coincide, numerous intermediates 



Explanation of Figures 16, 17 



FIG. 16. Distribution of S. latifolia var. pubescens. a, achene, X 3. b, bracts, x"^. 

 FIG. 17. Distribution of S. latifolia var. latifolia, a, achene, X 3. b, bracts, X %, c, stamen, 

 X 3. d, mature pistillate flower, X %. 



