3()7 
Geography. Common in extra- tropical countries, but also found near 
the equator. Potamogetons are in every ditch and swamp as far north as 
Iceland. 
Properties. Very unimportant. The root of Potamogeton natans is said 
to be eaten in Siberia. Zostera, or Sea wrack, is a common material for pack- 
ing, and for stuffing cottagers’ cushions. 
GENERA. 
Najas, L. 
Caulinia, Willd. 
Flavians, Pers. 
Zostera, L. 
Thalassia, Banks. 
Posidonia, Keen. 
Kernera, Willd. 
Caulinia, DC. 
Halophila, Pet, Thou. 
Barkania, Ehrenb. 
Zannichellia, L. 
Alteinia, Petit. 
Bellevalia, Del. 
Ruppia, L. 
Graumiillera, Reich. 
Potamogeton, L. 
Peltopsis, Rafin. 
Cymodocea, Keen. 
Phucagrostis, Cav, 
Epigynanthus, Bl. 
Order CCLXV. JUNCAGINACE^. 
JuNCAGiNE^, Rich. Anal. Fr. (1808) ; Mem. Mus. 1. 364. (1815) ; Lindl. Synops. 252. 
(1829) ; DC. and Duby, 438. (1828), a sect, o/ Alismaceae. 
Essential Character. — Sepals send petals both herbaceous, rarely absent. Stamens 6. 
Ovaries 3 or 6, superior, cohering firmly ; ovules 1 or 2, approximated at their base, erect. 
Fruit dry, 1- or 2-seeded. Seeds erect; albumen wanting; embryo having the same 
direction as the seed, with a lateral cleft for the emission of the plumule . — Herbaceous 
bog-plants. Leaves ensiform, with parallel veins. Flowers in spikes or racemes, incon- 
spicuous. 
Affinities. The plumule lying within a cleft on one side of the embryo 
fixes these plants nearer Araceae than Alismaceae, to which they are some- 
times referred, principally on account of their want of albumen ; and the 
depauperated state of their floral envelopes confirms the relationship. Junca- 
ginaceae are most nearly allied to Fluviales, which are readily distinguished by 
their floating habit and pendulous ovules. The genus Scheuchzeria is a tran- 
sition from Juncaginaceae to Juncaceae. 
Geography. Marshy places in most parts of the world maybe expected 
to indicate traces of this order, which is found in Europe, Asia, and North 
America, the Cape of Good Hope, and equinoctial America. 
Properties. Unknown. Triglochin has a salt taste. 
GENERA. 
Triglochin, L. Tetroncium, W. 
Scheuchzeria, L. Lilaea, H. et B. 
Order CCLXVI. PISTIACE^. The Duckweed Tribe. 
PisTiACE^, Rich, in Humb. et Bonpl. N. G. et Sp. 1. 81. (1815); Lindl. in Hooker’s 
FI. Scot. 2. 191. (1821); Synops. 251. (1829). — LEMNACEiE, DC. arid Duby, 532. 
(1828). 
Essential Character. — Flowers 2, naked, enclosed in a spathe. Male : Stamens 
definite. Female : Ovary 1 -celled, with 1 or more erect ovules ; style short ; stigma sim- 
ple. Fruit membranous or capsular, not opening, 1- or more-seeded. Seeds with a fun- 
gous testa, and a thickened indurated foramen ; embryo either in the axis of fieshy albumen, 
and having a lateral clefi for the emission of the plumule, or at the apex of the nucleus. 
