NAIADACE.E OR POTAME^ RESTIACE^;. 535 



1092. Order 207. iVaiadacetc or Potamete, the Naias or Pondweed 

 Family. (Mono-hypog.) Flowers hermaphrodite or unisexual. Pe- 

 rianth of two or four herbaceous or scaly pieces, often deciduous, 

 sometimes 0. Stamens definite, hypogynous. Ovary free, of one or 

 more carpels ; ovule solitary ; style 1 or stigma 



entire, rarely 2-3-parted. Fruit dry, 1-celled, 

 usually indehiscent. Seed solitary, erect, or pendu- 

 lous, exalbuminous; embryo straight or curved, 

 usually with a lateral slit for the plumule (fig. 758); 

 radicle large (figs. 499, 758). Plants living in 

 fresh and in salt water, having cellular leaves with parallel veins and 

 inconspicuous flowers. They are found in various parts of the world. 

 They have no properties of importance. Zostera marina, is used in 

 the dried state for stuffing mattresses, and has been recommended for 

 hospitals. Ouvirandra (Hydrogetori) fenestralis has peculiar skeleton- 

 like leaves (fig. 131). Aponogeton distachyum, a Cape aquatic, has 

 grown well for many years in the open pond of the Edinburgh Botan- 

 ical Garden. Caulinia fragilis is one of the plants in which Eotation 

 has been observed. There are 19 known genera, and upwards of 70 

 species. Examples Naias, Zannichellia (fig. 505), Potamogeton (fig. 

 130), Euppia, Zostera. 



1093. Order 208. Kestiaceie, the Restia or Cord-rush Family. 

 (Mono-perigyn.} Flowers frequently unisexual. Perianth glumaceous, 

 sometimes 0. Stamens definite, perigynous, when two or three in 

 number opposite the inner glumes; anthers usually 1-celled. Ovary 

 1 or more celled, sometimes composed of several carpels ; ovules soli- 

 tary, pendulous; styles and stigmas 2 or more. Fruit capsular or 

 uucumentaceous. Seeds pendulous; embryo lenticular, outside mealy 

 albumen, remote from the hilum. Herbs or undershrubs, with narrow 

 simple leaves or none, naked or sheathed culms, and spiked or capi- 

 tate, bracteated flowers. They are found chiefly in America and 

 New Holland. They have few properties of importance. The tough 

 wiry stems of Willdenovia teres and some Restias, are used for making 

 baskets and brooms. Eriocaulon septangulare is a native of Britain, 

 being found in the Isle of Skye, as well as in the west of Ireland. In 

 Brazil there exist branched Eriocaulons six feet high. In 1 7G4, Linnaeus 

 described only 5 species of Eriocaulon in all the world, while Gardner 

 collected in Brazil 100 species. The Diamond districts of Brazil arc 

 great centres of Eriocaulons. There are, according to Lindley, 3(J 

 genera, and 286 species. Examples Restio, Centrolepis, Eriocaulon. 



Fig. 758. Embryo of Zostera in the natural order Naiadaceae. c, Cotyledon, r, Radicle. 

 li. Lateral swelling connected with the radicle. /, Slit for the plumule, which lies in a cavity of 

 the very large radicle. 



