NAIADACEA. 709 
most abundant in temperate and cold regions.  Tilustrative 
Genera :—Triglochin, Linn. ; Potamogeton, Linn. There are 
about 50 species. 
Properties and Uses.—Of little importance. 
Ouvirandra fenestralis, a native of Madagascar, is commonly known 
under the name of the Lattice-leaf plant, from its leaves resembling open 
lattice-work. Its roots are of a fleshy farinaceous nature, and form an 
article of food; hence the name Ouvirandram bywhich the plant is known 
in Madagascar, the literal meaning of which is Water-yam. 
Order 4. NAIADACEH, the Pondweed Order.— Character. 
Aquatic plants with jointed cellular stems. Leaves with inter- 
petiolar membranous stipules. lowers small, unisexual (figs 
1070 and 1071), moncecious or dicecious, solitary or in spikes. 
Perianth either wanting, or present and composed of 2 or 4 
Fic. 1070. 
Fic. 1071. Fie. 1072. 
Fig. 1073. 
Fig. 1070. Two flowers of the Horned Pondweed (Zannichellia palustris), one 
staminate, the other pistillate-—— Fig. 1071. The gynecium of the same, 
composed of four perfect carpels, and one imperfect. —Fig. 1072. Vertical 
section of one of the carpels. Fig. 1073. Vertical section of the fruit 
and seed. All magnified. After Lindley. 
parts, which are then free and scale-like. Stamens 1 or few, 
hypogynous ; pollen globose or tubular. Carpels 1 or more, 
distinct, with superior ovaries (fig. 1071); ovule solitary (fig. 
1072). Fruit 1-celled, 1-seeded (jig. 1073). Seed exalbumi- 
nous ; embryo with a lateral cleft. 
Distribution.—They are widely distributed, but are chiefly 
found in extra-tropical regions. Illustrative Genera :—Naias, 
Willd. ; Zannichellia, Michel; Zostera, Linn. 
Propertiesand Uses.—Their properties are of little importance. 
Zostera marina, Sea-wrack, is in common use for packing, and for stuff- 
ing chairs, mattresses, &c., under the name of Alva ( Ulva or Alga) marina. 
It has also been recommended for paper-making, but it is a very unsuitable 
material for that purpose. 
