1955] 



REVISION OF THE GENUS SAGITTARIA 



217 



S, angustifolia Lindl. Trie actual angusti folia is a terete, stiffly narrow-phyllodial 

 form of South America, which if maintained as a separate species would be named 

 S, pugioniformis L. as was discussed earlier under S. rhombifolia. As in other 

 species of Sagittaria, the remainder of the synonymy has resulted from the wide 

 distribution and variable leaf-shape of lancifolia. 



The two subspecies maintained here are readily separated on the basis of 

 bract and sepal characteristics and correlated geographical distribution. However, 

 intermediates commonly occur in the areas where the subspecies overlap and 

 occasionally far removed from these overlapping regions. Fassett (in litt.) pro- 

 poses a new taxon, var. calculosa, for these intermediates; however, this proposal 

 is not adopted here since this taxon has no definite range and its maintenance 

 would only produce many additional intermediates. The present writer includes 

 such plants in the subspecies within whose range they were collected. 



12. Sagittaria papillosa Buch. Abh. Nat. Ver. Brem. 2: 27. 1868. 



Sagittaria lancifolia var. papillosa (Buch.) Micheli in DC. Monogr. Phan, 3: 74. 1881. 

 Sagittaria trachysepala Engelm. ex Micheli in DC. Monogr. Phan. 3: 74. 1881. Nomen 

 nudum. 



Perennial with short thick rhizome. Leaves emersed with linear to narrowly 

 lanceolate blades 7-25 x 0.4-2 cm, the petioles 10-40 cm long. Scape 30-90 cm 

 long, with 5-10 whorls of flowers, typically branching from the lowest whorl. 

 Bracts ovate, moderately connate, densely papillose, 0.3-0.7 cm long. Pedicels 

 short, to 1.5 cm long. Sepals 0.4-0.6 cm long, somewhat papillose, reflexed. Petals 

 white, ca. twice as long as the sepals. Stamens 15-21, the linear glabrous fila- 

 ments 0.8-1.6 mm long, ca. equaling the subglobose anthers. Mature receptacle 

 0.6-1.0 cm in diameter; achenes cuneate, small, 1.1-1.5 x 0.7-1 mm, the remotely 

 crested dorsal wing ca. 0.2 mm wide, the ventral wing somewhat narrower, the 

 faces unadorned, the short, broad-based, more or less recurving beak to 0.2 mm 

 long, laterally inserted about one-third down the achene-body. (FIG. 12a-c.) 



Type collection: Drummond 423, Texas (holotype, not seen, University of 

 Gottingen; isotypes GH, MO). 



Distribution: Extreme south-central United States; fairly common in swamps, 

 bogs, and small ponds. Collections examined from Arkansas, Louisiana, Texas. 

 (FIG. 12.) 



Sagittaria papillosa is most closely related to 5". ambigua, and both probably 

 evolved from the S. graminea-S. lancifolia group, with which they share the non- 

 sagittate lea^-shape in addition to all the key characteristics of the subgenus 

 Sagittaria. The main difference is that S, papillosa and S. ambigua have glabrous 

 filaments while all species of the S, graminea group have pubescent filaments. 



S. papillosa is often confused with S. lancifolia subsp. media since they 

 commonly occur together in portions of their range. Both have papillose bracts 

 and sepals and a similar vegetative appearance. They are quite distinct, however, 

 in achenial and the above-mentioned filament characteristics. The short, stubby 

 rhizome of S. papillosa is often covered with the dried leaf-base remnants of 

 previous years which give it a unique bulbous appearance. 



13. Sagittaria ambigua J.G.Sm. Missouri Bot. Gard. Rep. 6: 22. 1894. 

 Perennial with rhizomes and/ or runners and corms. Leaves emersed with 



lanceolate to ovate blades 5-20 x 1-6 cm, the petioles 15-35 cm long. Scapes 



Explanation of Figures 14, 15 



FIG. 14. Distribution of S. graminea var. graminea, a, achene, X 3. b, bracts, Xl. 

 c, stamen, X 3. FIG. 15. Distribution of S. lancifolia, a-c, subsp. lancifolia, a, achene, 

 X 3. b, bracts, X 1. c, stamen, X 3. d, bracts of subsp. media, X 1. 



