458 
NAIADACEjSE. (pondweed family.) 
curved-spreading, bright green, shining and pellucid, evenly many* 
nerved. I have not seen the flowers or fruit. 
§ 5. Stipules wanting: leaves all opposite and immersed. 
16. P. densus, L. Leaves pellucid, elliptical or lanceolate, 
clasping; spike few-flowered, short-peduncled, reflexed in fruit; nut¬ 
lets beaked and keeled. — Bethlehem, Penn., Schweinilz (Beck.). 
Order 113. ALISMACEJE. (Water-Plantain Fam.) 
Marsh herbs, with scape-like flowering stems, and perfect 
or monoecious flowers, not on a spadix, furnished with both 
calyx and corolla : sepals and petals each 3, distinct. Ova¬ 
ries 3 - many , distinct or partly so, or if united separating 
at maturity, forming as many 1 -2 -seeded pods or achenia. 
Seed ascending or erect. Embryo without albumen. Sta¬ 
mens hypogynous, 6 to many; anthers extrorse, 2-celled. 
Leaves sheathing at the base. 
Synopsis. 
Suborder I. JUNCAGINEiE. The Arrow-grass Fam. 
Calyx and corolla colored alike (greenish). Seed anatropous, with 
a straight embryo. Leaves petiole-like, without a blade. 
1. Triglochin. Flowers perfect. Ovaries 3-6, united into one 
body around a central axis, separating in fruit. 
2. Scheuchzeria. Flowers perfect. Ovaries 3, nearly distinct. 
Suborder II. ALISMEiE. The Water-Plantain Fam. 
Calyx green and persistent. Corolla white, deciduous. Seed cam¬ 
py lotropous : embryo bent double or hook-shaped. Leaves common¬ 
ly furnished with a blade. 
3. Alisma. Flowers perfect, 6-androus: carpels numerous, whorled. 
4. Echinodorus. Flowers perfect, 7-21-androus : carpels capitate. 
5. Sagittaria. Flowers monoecious, polyandrous. Carpels capi¬ 
tate, winged. 
Suborder I. JUNCAGINEjE. The Arrow-grass FaM. 
XBIOLOCHIIli, L. Arrow-grass. 
Sepals and petals nearly alike (greenish), ovate, concave, de¬ 
ciduous. Stamens 6 : anthers oval, on very short filaments. P^' 
tils united into a 3 - 6-celled compound ovary : stigmas sessile • 
