12 Naiadaceae 



more in fruit; pedicels 1-3 cm. long at maturity; drupes with a 

 hard shell, 2 mm. long, ovoid oblique or gibbous at base, pointed 

 with the long style. 

 JBrackish streams along the coast. June-August. 



3. ZANNICHELLIA L. HORNED PONDWEED. 



Stems capillary, sparsely branched from a creeping rhi- 

 .zome. Leaves all submerged, filiform but flat, 1-nerved. 

 iStaminate and pistillate flowers in the same axil, en- 

 closed in the bud by a hyaline spathe-like envelope; 

 staminate solitary, with 2-celled anther on a short pedi- 

 cel-like filament ; pistillate 2-5. Ovary flask-shaped, 

 stipulate at base, tapering into a short style with a broad 

 cup-shaped stigma, its margins angled or dentate. Fruit 

 a flattish falcate nutlet, ribbed or sometimes toothed on 

 the back. 



1. Z. palustris L. Stems 3-6 dm. high; leaves 2-6 cm. long; 

 spathe separating from the leaves and fruit at maturity ; fruits 

 2-6 in a cluster, 2-4 mm. long, sessile or short pedicelled, some- 

 times the whole cluster peduncled ; style persistent, straight or 

 curved, 1-2 mm. long. 



Occasional in marshes and ponds. 



4. NAIAS L. NAIAD. 



Stems slender, branching, from fibrous roots. Leaves 

 all submerged, opposite or whorled, spiny-toothed, 

 sheathing at the base. Flowers monoecious or dioecious, 

 axillary, solitary, sessile or pedicelled. Staminate with a 

 double perianth ; the outer entire or 4-toothed at the apex, 

 the inner one hyaline, adhering to the anthers. Stamens 

 sessile or stalked ; anthers 1-4-celled, apiculate or 2-lobed 

 at the summit. Pistillate flowers of a single ovary, 

 which tapers into a short style ; stigmas 2-4, subulate. 

 Fruit a solitary carpel, sessile, ellipsoidal, with a crusta- 

 ceous pericarp. 



