NAIADES. 



785 



II. NAIAD. NAIAS. 



Slender, branching, submerged plants, with linear, opposite or ter- 

 nate leaves, often crowded into whorls or clusters, and usually toothed. 

 Flowers small and sessile, often clustered with the branch-leaves in the 

 axils, and dioecious or rarely monoecious; the males consisting of a 

 single, nearly sessile anther, enclosed in a little membranous bract ; 

 the females of a single ovary, sessile in the sheathing base of the leaf, 

 with 2 to 4 subulate stigmas. Fruit a small, seed-like nut. Embryo 

 straight. 



A genus of few species, widely spread over a great part of the 

 globe. 



1. Slender Naiad, Naias flexilis, Eostk. (Fig. 944) 



Leaves narrow-linear, usually in 

 whorls of 3, or sometimes opposite, 

 often clustered in the axils, about 6 

 or 8 lines long ; the teeth few and 

 very minute. Stigmas usually 3, 

 sometimes 4. Fruit oblong, about a 

 line long. 

 A common North American species, 

 observed in a few scattered localities 

 in Europe, and recently detected by 

 Mr. D. Oliver in Connemara, in Ire- 

 land. Fl. summer. 



Fig. 944. 



III. ZANNICHBIiIiIA. ZANNICHELLIA. 



A genus limited to a single species ; differing from the narrow- 

 leaved Pondweeds by the monoecious flowers sessile in the axils and 

 without perianth, from Buppla in the usually opposite leaves, in the 

 single stamen with a long filament, and in the shape of the fruit. 



1. Common Zannichellia. Zanniehellia palustris, Linn. 

 (Fig. 945.) 



(Eng. Bot. t. 1844. Horned Pondweed.) 

 Stems slender, branched, and floating. Leaves finely linear, bright 



