WATER PLANTAIN FAMILY. 456 



E. rostriLtus, Engelm. Leaves broadly heart-shaped (l'-3' long, not 

 including the petiole), shorter than the erect scape, which bears a panicle 

 of proliferous umbels ; flower almost J' wide ; 12 stamens; akenes beaked 

 with slender styles. 111., W. and S. ® 



E. radlcans, Engelm. Leaves broadly heart-shaped and larger (3'-8' 

 wide), which are very open or almost truncate at base ; the creeping 

 scapes or stems becoming l°-4° long and bearing many whorls ; flowers 

 ^'-4' broad ; akenes short^beaked. 111., \V. and S. 2/ ? 



3. SAGITTAHIA, ARROWHEAD. (From the Latin for arroic, 

 on account of the sagittate leaves which prevail in the genus.) In 

 shallow water ; flowers all summer. 2/ 



* Filaments long and slender, i.e. as long as the linear-oblong anthers. 



S. variabilis, Engelm. The common species everywhere, exceedingly 

 variable ; almost all the well-developed leaves arrow-shaped ; filaments 

 nearly twice the length of the anthers, smooth ; sepals reflexed after 

 flowering ; akenes broadly obovate, with a long and curved beak ; calyx 

 remaining open. The lobes of the leaves are sometimes very narrow- 

 linear (var. gracilis, Engelm), and sometimes the petioles, upper part 

 of the scape, the bracts, and sepals are pubescent (var. pub^scens, 

 Engelm). Other well-marked forms occur. 



S. Montevidensis, Cham. & Schtecht. From S. Ainer., now frequently 

 grown in aquaria ; distinguished from the above by a deep purple spot at 

 the base of the flower inside, thick pedicels of the pistillate flowers, and 

 sepals erect after flowering. 



S. lancifdlia, Linn. Common from Md. and Ky., S. ; with the stouv' 

 leaves l°-3° and scapes 2°-5° high, the coriaceous blade of the former 

 lance-oblong and always tapering into the thick petiole, the nerves nearly 

 all from the thick and prominent midrib. 



S. calycina, Engelm. Along rivers, often much immersed ; many of 

 the leaves linear or with no blades ; the others mostly halberd-shaped ; 

 scapes weak, 3'-9' high ; pedicels with fruit recurved ; filaments roughish, 

 only as long as the anthers ; akenes obovate, tipped with short horizontal 

 style ; calyx appressed to head of fruit and partly covering it ; the fertile 

 flowers show fl-12 stamens, the sterile occasionally some rudiments of 

 pistils. Me., W. and S. 



* * Filaments very short and broad. 



S. heterophylla, Pursh. Scapes 8'-2° high, weak ; the fertile flowers 

 almost sessile, the sterile long-pediceled ; filaments glandular-pubescent ; 

 akenes narrow-obovate, with a long, erect beak ; leaves linear, lanceolate 

 or lance-oblong, arrow-shaped with narrow lobes or entire. N. Eng., 

 W. and S. 



S. gramfnea, Michx. Common S. ; known from the foregoing by 

 the slender pedicels of both kinds of flowers ; small, almost beakle.ss 

 akenes ; and leaves rarely arrow-shaped; the phyllodia flat. N. Eng., 

 W. and 8. 



S. t^res, Watson. N. Eng. to N. J., in shallow water ; scape 6'-20' 

 high ; pliyllodia terete, acutely attenuate upwards, very rarely with a 

 narrow blade ; pedicels all very slender and spreading, in 1-3 whorls ; 

 filaments 12, dilated and pubescent ; akene obovate, with an erect beak, 

 the margins crenate-cre.stcd. 



S nutans, Michx., var. lor^ta, Chapui. Known by the .small size 

 (l'-3' liigh), few flowers, usually only one of them fertile and recurved 

 in fruit ; stamens only about 7, with glabrous filaments ; akenes obovate, 

 with erect beak ; and leaves without a true blade. N. Y., S., near the 

 coast. 



