NAIADACE.I-:. (l'(>Nl>Wi:i:i) FAMILY.) 56j 



5. ZANNICHELLIA, Michdi. IIoknkd Povdweed. 



Flowers monoecious, sessile, naked, usually hoth kinds from the same axil ; 

 the sterile consisting of a single stamen, with a slender filament bearing a 2- 

 4-collcd anther; the fertile of 2-5 (usually 4) sessile pistils in the same cup- 

 sliaped involucre, forming oblitjuely ohlong nutlets in fruit, heaked with a short 

 style, which is tipped l>y an oldi(iuely disk-shaped or somewhat 2-lohed stigma. 

 Seed orthotropous, suspended, straight. Cotyledon taper, bent and coiled. — 

 Slender branciiing herbs, growing under water, with mostly opposite long and 

 linear thread-form entire leaves, and slieatliing membranous sti{)ules. (Named 

 in honor of Zdnnichelli, a Venetian botanist.) 



1. Z. pallistris, L. Style at le;ist half as long as the fruit, which is flat- 

 tish, somewhat incurved, even, or occasionally more or less toothed on the back 

 (not wing-margined in our plant), nearly sessile ; or, in var. peduncuiAta, 

 both tlie cluster and the separate fruits evidently peduncled. — Ponds and slow 

 streams, throughout N. America, but not common. July. (Eu., Asia.) 



6. ZOSTER A, L. Guass-wuack. Eel-grass. 



Flowers monan-ious; the two kinds naked and sessile and alternately ar- 

 ranged in two rows on the midrib of one side of a linear leaf-like spadix, which 

 is hidden in a long and slieath-like base of a leaf (spathe) ; the sterile flowers 

 consisting of single ovate or oval I -celled sessile anthers, as large as the ovaries, 

 and containing a tuft of threads in place of ordinary pollen ; the fertile of single 

 ovate-oblong ovaries attaclied near their apex, tapering upward into an awl- 

 shaped style, and containing a pendulous orthotropous ovule ; stigmas 2, long 

 and bristle-form, deciduous. Utricle bursting irregularly, enclosing an oblong 

 longitudinally ribbed seed (or nutlet). Embryo short and thick (proper cotyle- 

 don almo.st obsolete), with an open chink or cleft its whole length, from which 

 protrudes a doubly curved slender plunmle. — Grass-like marine herbs, grow- 

 ing wholly under water, from a jointed creeping stem or rootstock, sheathed 

 by the bases of the very long and linear, obtuse, entire, grass-like, ribbon-shaped 

 leaves (whence the name, from (uiar-np, a band). 



1. Z. raarina, L. Leaves obscurely 3-5-uerved. —Common in shoal 

 water of bays along the coast, from Newf. to Fla. (Eu.) 



7. NAIAS, L. Nalvd. 



Flowers dicecious or mona'cious, axillary, solitary and .sessile; the sterile 

 consisting of a single stamen enclosed in a little meml)ranous spathe ; anther at 

 first nearly sessile, the filament at length elongateil. Fertile flowers consisting 

 of a single ovary tapering into a sliort style ; stigmas 2-4, awl-shaped ; ovule 

 erect, anatropous. Fruit a little seed-like nutlet, enclosed in a loose and separ- 

 able membranous epicarp. Embryo straight, the radicular end downward. — 

 Slender branching herbs, growing under water, with opposite and linear leaves, 

 somewhat crowded into whorls, spinulose-toothed, sessile and dilated at base. 

 Flowers very small, solitary, but often clustered with the branch-leaves in the 

 axils; in summer. {^ aids, a uater-ni/mph.) 



1. N. marinE, E. Stnn rather stout and o/ieiionned irithhroad prick/fs; 

 leaves bmadli/ linear (3 - 18" long), coarseli/and sharpli/ toothed, the dilated base 

 entire; fru^t 2-2^" long; seed ver;/ Jinely Hneate. oft/on^r, slightly compressed. 



