672 OEDER 134. NAI ADAGES. 



2. SPAR'GANUM, L. BURR REED. (Gr. orrdpyavov, a band or fil- 

 let ; in reference to the long, ribbon-like leaves.) Spadiees many, glob- 

 ous, the lower fertile, the upper consisting of numerous stamens with 

 scales intermixed ; filaments slender ; anthers oblong-linear, 2-celled ; 

 ? pistils numerous, sessile, eacli surrounded by 3 or 6 scales, which 

 represent a perianth ; stigma ligulate, unilateral, fruit nut-like, sessile, 

 1-seeded. U Aquatic herbs. St. leafy, simple or branched. Lvs. 

 long, linear, sheathing at base. 



Stigmas mostly 2. Stems of the inflorescence branching. Erect No. 1 



Stigmas always single. Stein simple. Erect. Heads large (half inch diuin.) No. 3 



Floating or erect. Heads small Nos. 3, 4 



1 S. ramosuxn Huds. Lvs. triangular at base, their sides concave; common 

 flower-stalks branched; stig. 2, linear. Grows in pools and ditches, where it is 

 conspicuous among other reedy plants for its globular burrs of flowers. Stem 

 1 -2f high, flexuous, round, with a few branches above. Leaves 2f long, 

 4 8" wide, linear, arising above the stem, triangular towards the base, and 

 sword-form upwards, tapering, but obtuse. Heads of flowers light green ; fertile 

 ones 2 5, 6" diam., the lowest generally raised on a short, axillary stalk; sterile 

 ones above, more numerous, smaller, sessile. Aug. 



2 S. simplex Smith. Lower Ivs. equal with, or exceeding the stem, which 13 

 nearly simple, floral ones concave at base and erect ; stig. always simple, ovate- 

 oblong, oblique, scarcely more than half the length of the style. Ponds and 

 lakes. Stem 1 2f high, simple or divided at base. Leaves mostly radical, 

 1 2^f by 3", carinate at base. Fertile heads sessile, generally 3, 6 to 8" diam., 

 below the several barren ones, with the simple styles conspicuous. Aug. (S. 

 Americanum Nutt.) 



3 S. natans L. Los. floating, flat; common flower-stalk simple ; stig. ovate, very 

 short ; head of sterile fis. subsolitary ; fruit beaked and stipitate. Lakes and pools, 

 U. S. and Brit. Am. Stem, long and slender, and, with the leaves, floating upon 

 the surface of tho water. Leaves thin and pellucid. Heads of fertile flowers 

 axillary, generally 2, small, mostly sessile. Sterile cluster terminal. Aug. 



4 S. angustifdlium MX. Slender, weak, simple, erect or floating ; Ivs. narrowly 

 linear, shorter than the stem when erect, elongated when floating ; heads very 

 small, axillary, the lower pedunculate ; stigma single, short ; jr. scarcely beaked, 

 sessile. N. Eng., N. Y., Can., pools and streams. Sts. 1 to 2f long, Ivs. 1 to 3 to 

 9' or more, obtuse. Hds. scarce a fourth of an inch diam. 



ORDER CXXXIV. NAIADACEJ3. NAIADS. 



Water plants with jointed stems, and sheathing stipules, or sheathing petioles. 

 Flowers perfect or diclinous, naked or with a 2 to 4-parted perianth. Stamens defi- 

 nite. Ovaries free, sessile, 1-ovuled. Stigma simple, often sessile. Fruit indehis- 

 cent. Seed without albumen, with a straight or curved embryo. 

 Genera 9, species GO, in waters and marshes, salt or fresh in all countries. 



GENERA. 



* Flowers axillary, sessile, the staminate reduced to a single stamen (a)- 



a Fertile flowers reduced to a single pistil, with 2 or 3 stigmas. Lvs. opposite. .NAJAS. 1 

 a Fertile flowers with about 4 pistils in a cup, with as many stigmas ZANICIIELLIA. 2 



* Flowers spadaceous, or 2 to 20, sessile on a spadix or spike (b). 



b Flowers monoecious, seated in 2 rows on the side of a linear, flat spadix ZOSTEBA. 3 



b Flowers perfect, naked, 2 to 5, 4-inerous ; fruit raised on slender stipes RUPPIA. 4 



b Flowers perfect ; perianth 4-sepaled ; etam. 4. Pistils and achenia 4. . POTAMOGETON. 5 



1. NAM AS. L. WATER NYMPH. (Gr. i>ao>, to flow ; hence Naif, or 

 Ntu'fcf, Nymph of the waters ; from the habitat.) Flowers axillary, 

 sessile, solitary, the <$ reduced to a single stamen ; filament slender, 



