440 HYDROCHARIDACE^;. (FROG'S-BIT FAMILY.) 



7 -9 ; ovaries short-pointed (ripe fruit not seen). (Alisma subulata, Pursh.) — 

 Low shores, near Philadelphia, &c. —Apparently distinct from dwarf forms of 

 the last ; but needs further investigation. 



S. nAtans, Michx., apparently the only remaining good species in the Unit- 

 ed States, is only found farther south. 



Order 117. HYDROCHARIDACE^S. (Frog's-bit Fam.) 



Aquatic herbs, wit-h dioecious or polygamous regular flowers on scape-like 

 peduncles from a spathe, and simple or double floral envelopes, lohich in the 

 fertile flowers are united into a tube and coherent ivith the 1 - 0-celled ovary. 

 Stamens 3-12, distinct or monadelphous : anthers 2-celled. Stigmas 3 or 

 6. Fruit ripening under water, indehiscent, many-seeded. Seeds ascend- 

 ing, without albumen : embryo straight. 



Synopsis. 



Tribe I. STRATIOTIDE.33. Ovary 6 - 9-celled : stigmas 6 - i>. 



1. LIMNOBIUM. Filaments unequally united into a solid column in the staminate flowers • 



anthers 6 - 12, linear. 

 Tribe II. VAL.liISNERIE.3E. Ovary 1-celled, with 3 parietal placentas : stigmas 3. 



2. ANACHARIS. Stem leafy. Tube of the perianth of the fertile flowers long and thread- 



form ; its lobes 6. 



3. VALLISNERIA. Stemless. Tube of the perianth not prolonged beyond the elongated 



ovary ; its lobes 3. 



1. LIMNOBIUM, Richard. American Frog's-bit. 



Flowers dioecious, (or monoecious 1) from sessile or somewhat peduncled 

 spathes ; the sterile spathe 1-leaved, producing about 3 long-pedicclled flowers ; 

 the fertile 2-leaved, with a single short-pedicelled flower. Calyx 3-parted or 

 cleft ; sepals oblong-oval. Petals 3, oblong-linear. Filaments entirely united 

 in a central solid column, bearing 6-12 linear anthers at unequal heights : there 

 are 3-6 awl-shaped rudiments of stamens in the fertile flowers. Ovary 6-9- 

 celled, with as many placenta? in the axis, forming an ovoid many-seeded berry 

 in fruit : stigmas as many as the cells, but 2-parted, awl-shaped (ovules orthotro 

 pous, Ton-.).— A stemless perennial herb, floating in stagnant water, prolif- 

 erous by runners, with long-petioled and round-heart-shaped leaves, which are 

 spongy-reticulated and purplish underneath; rootlets slender, hairy. Sterile 

 flowers rather small ; the fertile larger : peduncle nodding in fruit. Petals 

 white ? (Name from Xtfivo^ios, living in pools.) 



1. I,. Spongia* Richard. (Hydroc'naris, Bosc. H. cordifolia, Nutt.) — 

 Braddock's Bay (Monroe County, N. Y.), Lake Ontario, Dr. Bradley, Dr. Sart- 

 wdl, Illinois, Vasey, and in the Southern States. Aug. — Leaves l'-2' loug, 

 faintly 5-nerved. Peduncle of the sterile flower about 3' long, thread-like ; of 

 the fertile, only 1 ', stout. 



