XXII. NATADEuE. 807 



2-3-fid spike, at the top of an axillary scape, enclosed at first in a membranons 

 or coloured conical spatlie. Perianth 0, or 2-3-pliyllo-us, caducous or persis- 

 tent, sometimes accompanied by 10-15 distichous white thick and accrescent 

 bracts (Aponogeton) . Stamens 6-18-20, hypogynous, sub-equal ; /kmewfe subulate, 

 persistent ; anthers ovoid, basifixed, 2-celled ; pollen globose, or acutely elliptic. 

 Ovaries 3-5, flagon-shaped, sessile, 1-celled ; style continuous with the ovary, 

 oblique, and stigmatiferous on the inner face ; ovules 2-4-6, inserted a little to one 

 side at the bottom of the cell, ascending, anatropous. Teuit a 1-2-seeded follicle. 

 Seeds with membranous or sub-spongy testa ; albumen 0. Embeto oval or elliptic, 

 thick, compressed, radicular end inferior. 



GENERA. 

 * Aponogeton. * Ouvirandra. 



\_Aponogeton is very closely allied to Potamece, and is distinguished chiefly by the hiacts, hypo- 

 gynous stamens, and sub-hasal ovules.] 



These genera belong to tropical Africa, India, and Madagascar. The name Chmrundra is taken from 

 the Madagascar language, in ■which the -word ouvirandrou signifies edible root, and is applied equally to 

 several species of iJioscorea ; the root o?«« is found bearing the same meaning throughout the islands of 

 the Southern Ocean. We have noticed elsewhere that the genus Spathium, of Loureiio, is a synonym of 

 Sam~a)rix. 



XXII. NAIADEjE. 



Marine or fresh-water annual or perennial herbs. Stems creeping or rooting, 

 branched. Leaves alternate, distichous or opposite, often close together at the top 

 of the internodes, linear, 1-3-nerved, entire, or tip denticulate, base sheathing, 

 persistent, or jointed and caducous : sheath furnished with intravaginal free or connate 

 membranous stipules, sometimes accompanied by scales [Phucagrostis) ; spadices 

 usually solitary, sometimes several united in a common spathe, each furnished with 

 a 2-valvedspathella, and bearing 3-6 § flowers (Posti^oma). Flowers S {Posidonia), 

 or monoecious {Zostera), or dioecious {Najas, Phucagrostis); solitary {Phucagrostis), or 

 sub-solitary {Najas), or in axillary fascicles {Caulinia), or united, 2 or more, on a 

 spadix contained in a foliaceous spathe. Peetanth {Zostera, Phyllospadix, Phuca- 

 grostis, Posidonia, &c.); or tubular, membranous, 4-lobed {Caulinia, Najas), or tnhular, 

 denticulate {Ealophila). Stamens 1 {Najas, Caulinia, Zostera, &c.), or 2 {Phuca- 

 grostis), or 4-3 {Posidonia) ; filaments {Najas), or very short, scale-like {Zostera), or 

 dilated and aristate {Posidonia), or geminate and coherent {Phucagrostis); anthers 1- 

 celled {Zostera), or 2-celled {Posidonia, Phucagrostis, &c.), or 4-celled {Caulinia, Najas), 

 dehiscence loi>gitudina\; pollen usually confervoid {Zostera, Phucagrostis, &c.), or 

 globose {Najas, Caulinia). Ovaries 1-2-4, distinct, 1-celled, usually 1-ovuled, 

 sometimes with 3 several-ovuled parietal placentas {Ealophila, Lemnopsis); stigmas 

 2 apiculate, or 3 filiform, sometimes jointed at the top of the style {Ealophila, &c.), 

 rarely discoid and sharply branching {Posidonia) ; ovule pendulous and orthotropous 

 {Zostera), or campylotropous {Phucagrostis, &c.), or ascending and anatropous 

 {Caulinia, Ealophila, ,&c.). Fruit usually a nut or utricle, sometimes a_ berry 

 {Posidonia), indehiscent, or opening more or less irregularly at germination. Seed 



