82 ALISMACEAE (WATER-PLANTAIN FAMILY) 



winged on both margins, with a curved usually horizontal beak. (#. variables 

 Engelra.) In water or wet places, very common; exceedingly variable as to 

 leaf-contour. FIG. 34. The following forms, although ill denned, 

 are in most instances recognizable : Forma OBxtiSA (Muhl. ) 

 Robinson. (S. obtusa Muhl.) Leaves very broad, sagittate, ob- 

 tuse. Forma HAST.\TA (Pursh) Robinson. (S. hastata Pursh.) 

 Leaf-blades and their basal lobes oblong-lanceolate, acute. Forma 

 GRACILIS (Pursh) Robinson. (S.gracilis Pursh.) Leaf -blades and 

 their basal lobes narrowly linear. Forma DIVERSIFOLIA (Engelm.) 

 Achene x 3 RobinBon. (S. variabilis, var. Engelm.) Leaf -blades partly sagit- 

 tate and partly lanceolate or elliptic without basal lobes. 

 Var. pubscens (Muhl.) J. G. Sm. Robust, pubescent, broad- 

 leaved; bracts shorter than in the other forms, 6-9 mm. long, 

 broadly ovate, obtusish, and very pubescent. N. J. and Pa. to 

 N. C. 



3. S. Engelmanniana J. G. Sm. Slender; lobes of the 

 sagittate leaves very narrowly linear (1-3 mm. wide) ; achene 

 narrowly cuneate-obovate (4 mm. long), the beak elongated, erect 

 or recurved, the sides usually strongly 1-3-crested. (S. variabilis, 

 var. gracilis Engelm.) About ponds, etc., "N. H." and Mass, 

 to Del. FIG. 35. 



4. S. arif61ia Nutt. Monoecious, glabrous; scape 2-4 dm. 



high, simple or rarely branched ; fertile whorls l-(rarely)3 ; fertile pedicels 

 3-11 mm. long; leaf-blades sagittate-hastate, ovate, acute; achenes winged all 

 round, bearing at the upper inner angle a minute erect beak. 

 Que. to centr. Me., Vt., Ct., Mich., Kan., Dak., and westw. 

 When in deep water producing lance-linear phyllodia at the base 

 and developing elongated petioles of the blade-bearing leaves 

 (S. cuneata Sheldon). FIG. 36. 



5. S. brevir6stra Mackenzie & Bush. Very stout ; scape 6-12 

 1 ' a ' dm. high ; leaf-blades all sagittate, basal lobes ovate-lanceolate, 

 acute, about as long as the terminal portion ; inflorescence simple 

 or slightly branched, 2-5 dm. long ; bracts lanceolate, attenuate ; fruiting pedi- 

 cels 1-2 cm. long ; fruiting heads 2-3 cm. in diameter ; achenes cuneate-obovate, 

 with dorsal wing prominent ; beak suberect, but little surpassing the wing at 

 the summit. Sloughs and bottoms, Ind. to Kan. 



6. S. lancifblia L. Scape 8-15 dm. high, with several of the lower whorls 

 fertile ; leaves lanceolate or lance-oblong, rarely linear, all with a tapering base, 

 thick or coriaceous (1.5-4.5 dm. long on a long and stout petiole, never sagittate), 

 the nerves mostly arising from the very thick midrib ; bracts ovate, acute or acu- 

 minate ; pedicels slender, the fertile scarcely shorter than the 



sterile ones ; filaments pubescent ; achenes falcate, winged on the 

 back, pointed with an incurved beak. Swamps, Md. to Ky., Mo., 

 andsouthw. (W.I.) FIG. 37. 



7. S. ambigua J. G. Sm. Scape 4-6 dm. high ; leaves as in 



the preceding; raceme simple ; pedicels 1.5-2.5 cm. long; bracts ' ' 

 lanceolate, small (8 mm. long) ; filaments glabrous ; achenes 

 with a short incurved beak, scarcely winged. Borders of ponds, etc., Kan. 

 and souhtw. 



* * Filaments very short, with enlarged mostly glandular base ; anthers ovate or 

 ; fruiting heads small ; bracts more or less connate; leaves very 

 rarely sagittate. 



8. S. heterophylla Pursh. Scape weak (1.5-8 dm. high), 

 at length procumbent ; leaves lanceolate or lance-oval, entire, 

 or with one or two narrow basal sagittate appendages ; brm't* 

 roundish, obtuse; flowers of the lowest whorl fertile and almost 

 .sr.s-.s-///' ; the sterile on long pedicels ; filaments ulnndular- 

 pubescent ; achenes n<irr<>n-hj obovate with a long erect l>?nk. 

 Achene x3. N. E. to Fla., w. to Minn, and Mo. Varies as to foliage, the 



