450 HYDROCHARIDACEJE. (FROG's-BIT FAMILY.) 



ORDER 140. HYDROCHARIDACE^E. (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 placenta?, 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, 

 attd 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. 



