ORDER 135. ALISMACE^E 677 



clustered at the nodes, on long pedicels; stam. 1824; heads of carpels ovoid, 

 achenia short-beaked, very numerous (100 209). 1[ Swamps, W. 111. (Engel- 

 mann in Gray's Manual) S. to Ga. (Mettauer) and La. (Hale). Lvs. 5 12' by 

 3_7', strongly heart-shaped. Scapes several, 2 4f long, producing roots and 

 small leaves as well as flowers at the upper joints. Flowers white, muck resem- 

 bling those of Sagittaria. Jn., Jl. (Aliatna, Nutt.) 



2 E. rostratus Eugelm. Leaves mate, rather acute, cordate, about b-veined, the 

 later ones oblong, all long-petioled ; scapes erect, much exceeding the leaves, 

 sharply angled; stam. 12; Leads of carpels globular; ach. numerous (100), strongly 

 ribbed and beaked. (J) River swamps, 111. near St. Louis (Engelm.) S. to Ark. 

 Much smaller than the preceding. Lvs. 1 3' long, petioles 2 4'. Scapes 1 3fL 

 Flowers about half as large as in Sagittaria. ( Alisma, Nutt.) 



3 E. parvula Engelm. Dwarf; kaves elliptic-lanceolate, very acute, tapering to a 

 petiole of equal length; scapes erect, 3 G-flowered; pedicels reflexed in fruit; 

 stam. 9; heads of carpels depressed-globular; ach. about 20, beakl&ss. (D Muddy 

 shores. 111., Mo. to Mich. (Engelm.). Plant a few inches (13 or 4') high, often 

 stoloniferous. Leaves, excluding petiole, less than 1' long. Fls. about 3" 

 diameter. 



3. SAGITTARIA, L. ARROW-HEAD. (Lat. sagitta, an arrow ; from 

 the peculiar form of the leaf.) Flowers 8 , rarely $ $ , sepals 3 ; pet- 

 als larger, colored, aestivation imbricate ; stam. oo ; ovaries very nu- 

 merous, crowded into a head, forming in fruit as many flat, margined, 

 beaked achenia. Acaulescent marsh herbs, with a milky jnice. Lvs. 

 commonly arrow-shaped, often lanceolate, linear, or even reduced to 

 mere petioles. Scapes with fls. in whorls of 3s, the lower perfect. 

 Petals white. 



Lower (fertile) pedicels much shorter than the upper (sterile) ones Nos. 1, 2 



Fertile pedicels as long as the sterile, (a) 



a Filaments longer than the anthers. Lvs. not sagittate No. 8 



a Filaments very short. Leaves lanceolate and linear, mostly Js'os. 4 



Leaves oval-obtuse, sagittate at base No. 7 



1 S. variabilis Engelm. Lvs. generally sagittate; scape 12-angled, , upper fls. 

 sterile, on pedicels but twice longer than those of ifie lower fertile fls. ; fll. glabrous, 

 longer than the anthers ; ach. obovate, with a conspicuous, averted beak. A curious 

 aquatic, conspicuous among the Rushes and Sedges of sluggish waters, Can. and 

 U. S. Lvs. 3 to 10', the lobes about as long as the lamina, petioles much longer. 

 Scape 10' to 2f, simple or branched, 3 of the angles prominent. Fls. mostly in 3s, 

 vith ovate, slender-pointed bracts, often dioecious. Petals roundish, showy, 

 wholly white. JL, Aug. The leaves arc exceedingly variable. (S. sagittifolia, 

 Ed. 1, &c., nee. L., from which it differs, according to Dr. Engelmann, in the char- 

 acters emphasized above.) 



/3. OBTUSA. Lvs. large, broadly ovate, sagittate, apex obtuse; fls. dkecious. 



A large form, Mid., W. and S. States. "(S. obtusa Willd.) 

 y. LATIFOLIA. Lvs. large, broad-ovate, acute, with ovate, acuminate lobes. 



6. GRACILIS. Lvs. linear, with linear, long, acute, spreading lobes. 



F. PL'BESCKXS. Plant pubescent in all its parts ; Ivs. and their lobes ovate. 



2 S. heterophylla Ph. Lvs. smooth, linear-lanceolate, rarely some of them ellip- 

 tical and sagittate; scape simple, weak; bracts roundish, obtuse; upper fls. sterile, 

 on long pedicels, the lowest whorl fertile, almost sessile; fll. very short; ach. nar- 

 rowly obovate. long-beaked. Muddy shores, common S. and "YV. Leaves almost 

 as variable as in Xo. 1, but the other marks are very distinctive. Stalks If to sev- 

 eral, according to the depth of water. Blades 6 to 10' in length. Fls. large, 12 

 to 16" diam., white. July. 



/3. RIGIDA. Plant rather rigid in habit, erect ; Ivs. narrowly lanceolate ; acuto 

 at apex, acute or obtusish at bnse. -Lake shores. (S. rigida Ph.) 



7. ANGCSTIFOLIA. Lvs. nearly linear, delicate, often floating as well as the 

 weak, elongated scape. 



3 S. lancifolia L., MX. Lvs. lance-cblong, acutish, feather-veined, long-taper- 

 ing at base to a very long petiob; scape tall, branched; fls. in 3s, all long-pedi- 



