ALISMACEAE ( WATER-PLANTAIN FAMILY) 81 



mostly verticillate, in a loose raceme or panicle, with lanceolate scarious bracts 

 slightly connate at base. 



1. Sagittaria. Monoecious (or dioecious), lower (first developed) flowers pistillate, the upper 



(later) ones staminate. Stamens indefinite, mostly numerous. Carpels strongly flattened, 

 in a dense head. 



2. Lophotocarpus. Polygamous ; lower flowers perfect, the upper staminate. Stamens 9-15. 



Carpels strongly flattened, in a dense head. 



3. Echinodorus. Flowers all perfect. Stamens 6-21, mostly definite. Carpels somewhat 



turgid, in a dense head. 



4. Alisma. Flowers all perfect. Stamens usually 6. Carpels strongly flattened, in a single ring. 



1. SAGITTARIA L. ARROW-HEAD 



Sepals loosely spreading or reflexed in fruit. Petals imbricated in the bud. 

 Ovaries crowded in a spherical or somewhat triangular depressed head on a 

 globular receptacle, in fruit forming flat membranaceous winged achenes. 

 Marsh or aquatic, mostly perennial, stoloniferous herbs, with milky juice ; 

 the scapes sheathed at base by the bases of the long cellular petioles, of which 

 the primary ones, and sometimes all, are destitute of any proper blade (i.e. are 

 phyllodia) ; when present the blade is arrow-shaped or lanceolate. Flowers 

 produced all summer, whorled in threes, with membranous bracts. (Name 

 from sagitta, an arrow, from the prevalent form of the leaves.) 



a. Beak of the achene erect or nearly so &. 

 b. Beak long, usually half to three-fourths the length of the body. 



Leaves habitually sagittate, the basal lobes nearly or quite as 

 long as the terminal portion of the blade. 



Stout ; leaf-blades broadly ovate-oblong 1. S. longirostra. 



Slender ; leaf-blades linear 8. S. Engelmanniana. 



Leaves lanceolate to elliptical, the basal lobes when present 



much shorter than the terminal portion . . . 8. 8. heterophylla. 



6. Beak very short, not one-fourth the length of the body. 

 Leaves all or most of them sagittate, ovate. 



Lowest bracts 0.5-1.5 cm. long; leaf-blades 2-18 cm. long . 4. S. arifolia. 

 Lowest bracts 2-4 cm. long ; leaf-blades 2.5-5 dm. long . . 5. S. brevirostra. 

 Leaves never sagittate. 



Fruiting pedicels thickish, recurved 11. S. subulata. 



Fruiting pedicels slender, ascending or spreading . . .10. S. leres. 

 a. Beak of the achene strongly incurved, almost or quite horizontal c. 

 c. Leaves habitually sagittate, the basal lobes nearly or quite as long 



as the terminal portion 2. S. latifolia. 



o. Leaves linear to elliptic-ovate, entire or rarely sagittate at the base, 

 the basal lobes when present much shorter than the terminal 

 portion of the blade. 



Fertile pedicels thickened, recurved ; western . . . . 12. S. plfityphylla. 

 Fertile pedicels slender, ascending or spreading. 



Filaments thickened at the base, short 9. S. graminea. 



Filaments slender, longer than the anthers, pubescent . 6. S. lancifolia. 



Filaments slender, longer than the anthers, glabrous . 7. S. ambigua. 



* Filaments numerous, narrow, as long as or longer than the linear-oblong 

 anthers; bracts 3, distinct; fruiting heads large. 



1. S. Iongir6stra (M. Micheli) J. G. Sm. Robust, 3-6 dm. high, monoecious ; 

 leaves broadly ovate-oblong, obtusish, sagittate with broad basal lobes ; fertile 

 whorls 2-4 ; fertile pedicels about 1 cm. long ; body of the mature achene obovate, 

 winged all round, 3 mm. long, the beak nearly erect from the 



inner angle, 1.5-2 mm. long. About springs, etc., Ct. (Harger), 

 N. J., and Pa. to Ky., Del., and Ala. FIG. 33. 



2. S. latif&lia Willd. Glabrous; scape 1-9 dm. hi^h, angled, 

 with one or more of the lower whorls fertile ; leaves ovate, acute, 

 almost always sagittate, the basal lobes triangular, acute ; pedi- 

 cels of the fertile flowers at least half the length of the sterile 



ones ; petals wholly white ; filaments glabrous, nearly twice the 83. S. longirostra 

 length of the anthers; achenes obovate (about 2 mm. long), Athene x 8. 

 GRAY'S MANUAL 6 



