Alisma. ALISMACE^. 259 



Borders of ponds, and overflowed miry places. Fl. July - August. Fr. September. 

 Variable in size, and in the number of nerves in the leaves. I can discover no essential 

 difierence between the European plant and ours, though Pursh considered them distinct, and 

 even made two distinct species of the latter. 



2. SAGITTARIA. Linn. ; Endl. gen. 10^2. arrowhead. 



LFrom sagitla, the Latin for arrow ; the leaves being mostly of that form.] 



Flowers usually monoecious or polygamo-monoecious. Calyx of 3 persistent sepals. Petals 

 3, deciduous ; the aestivation imbricate. Stamens numerous. Ovaries very numerous, 

 crowded into a head, distinct, each with a single erect campulitropous ovule. Carpels 

 compressed, rostrate with the short persistent style. — Marsh or aquatic plants, with radical 

 petiolate and mostly sagittate or hastate leaves and a milky juice. Scapes many-flowered, 

 with the flowers usually verlicillate in threes ; the staminate ones above. 



1. Sagittaria sagittifolia, Linn. Common Arrowhead. 



Leaves sagittate, or sometimes entire ; scape simple. — Linn. sp. 2. p. 993 ; Hook. fl. 

 Bor.-Am. 2. p. 167. 



var. 1 . vulgaris : leaves ovate, acute or acuminate ; the lobes ovate-lanceolate, straight, 

 acuminate. — Hook, I. c. S. sagittifolia, Michx.fl. 2. p. 189 ; Pursh, fl. 2. p. 395 ; Ell. sk, 

 2. p. 589 ; Bigel. fl. Bost. p. 344 ; Beck, hot. p. 377 ; Darlingt. fl. Cest. p. 528. 



var. 2. latifolia : leaves very large and broad, more or less obtuse ; the lobes ovate- 

 lanceolate and spreading. — Torr. compend. p. 855 ; Beck, I. c. ; Kunth, enum. 3. p. 1 56. 

 P. sagittifolia, var. macrophylla, Hook, I. c. S. latifolia, Willd. sp. 4. p. 408 ; Pursh, fl. 2. 

 p. 396. 



var. 3. hastata : leaves oblong-lanceolate, acute ; the lobes divaricate, lanceolate, elongated ; 

 flowers mostly dioecious. — Torr. I. c. ; Beck, I. c; Kunth, I. c. S. hastata, Pursh, I. c. ; 

 Ell. I. c. 



var. 4. gracilis : leaves lanceolate-linear ; the lobes much divaricate, linear, very long, 

 acute, or sometimes wanting. — Torr. I. c. ; Beck, I. c. ; Kunth, I. c. S. gracilis, Pursh, I. c. 

 S. heterophylla. 



var. 5. pubescens : leaves and scape pubescent — Torr. 1. c. ; Beck, I. c. ; Darlingt. I. c.'; 

 Kunth, I. c. S. pubescens, Pursh, I. c. ; Kunth, I. c. 



var. 6. simplex : leaves all with the lamina linear-lanceolate, and destitute of lobes. — 

 Hook. I. c. S. simplex; S. graminea ; and S. acutifolia, Pursh, I. c. ; Kunth,'l. c. 



var. 7. rigida : leaves narrowly lanceolate, very acute at each end, carinate below. S. 

 rigida, Pursh, I. c. 



Root perennial, consisting of thick fibres, and producing oval fleshy tubers which abound in 

 Btarch. Leaves extremely variable ; the lamina being sometimes 8-10 inches long (including 



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