450 IIYDROCHARIDACE.E. (FROG'S-BIT FAMILY.) 



ORDER 140. HYDROCHARIDACEJE. (FROG'S-BIT 

 FAMILY.) 



Aquatic herbs, with monoecious or dioecious flowers, from a membrana- 

 ceous spathe. Sepals and petals 3, or the latter wanting, distinct in the 

 sterile flower, united into a tube in the fertile, and coherent with the 1-9- 

 celled ovary. Stamens 3-12. Ovules numerous, ascending, orthotropous. 

 Stigmas 3-9. Fruit indehiscent, many-seeded. Embryo straight, without 

 albumen. 



Synopsis. 



* Ovary 1-celled. Stigmas 3. 



1. ANACHARIS. Flowers polygamo-dioecious. Spathe sessile. Stamens 9. Leaves short, 



opposite or whorled. 



2. VALLISNERIA. Flowers dioecious. Spathe peduncled. Stamens 3. Leaves long, linear. 



* * Cells of the ovary and stigmas 6-9. 



3. LIMNOBIUM. Flowers monoecious. Stamens 6-9, monadelphous. Leaves cordate, 



petioled. 



1. ANACHARIS, Rich. 



Flowers dioeciously polygamous, enclosed in the bud in a 2-cleft axillary 

 sessile spathe. Sterile flowers minute. Sepals and petals 3. Anthers 9. Fer- 

 tile flowers pistillate or perfect. Sepals and petals united into a very long and 

 slender 6-parted tube. Stamens 3-6, perfect or sterile. Ovary 1-celled, with 

 three parietal placentae, few-ovuled. Style capillary, adnate to the tube. Stig- 

 mas 3, each 2-lobed, exserted. Fruit oblong, coriaceous. Perennial herbs, 

 with elongated filiform branching immersed stems, and small and very numer- 

 ous opposite or whorled leaves. Fertilization effected by the sterile flowers 

 breaking away from the stem, and expanding at the surface among the floating 

 stigmas. 



1 . A. Canadensis, Planch. Stem much branched ; leaves 3-4 in a 

 whorl, sessile, varying from linear to elliptical, 1 -nerved, pellucid and minutely 

 serrulate. (Udora Canadensis, Nutt.) In slow-flowing streams and ponds, 

 Cherokee, North Carolina, Curtis, and northward. July and Aug. Leaves 

 3" -6" long. 



2. VALLISNERIA, Micheli. TAPE-GRASS. 



Flowers dioecious. Sterile flowers numerous, minute, crowded on a spadix, 

 which is enclosed in an ovate 3-leaved short-stalked spathe. Calyx 3-parted. 

 Corolla none. Stamens 3. Fertile flowers solitary, enclosed in a tubular spathe, 

 and borne on a very long and mostly spiral scape. Sepals and small petals 3, 

 united and coherent with the cylindrical 1-celled many-ovuled ovary. Stigmas 

 3, each 2-lobed. Seeds numerous, fixed to three parietal placentae. Aquatic 

 herbs, with creeping stems, and elongated strap-shaped leaves. Fertilization 

 effected mostly as in Anacharis. 



