28 NAJADACEAE. 



Zannichellia palustris L. Horned Pondweed. Stems slender, branching, 

 leafy, 10-60 cm. long; leaves thin, filiform, 1-nerved, 5-8 cm. long; fruit nearly 

 sessile, flattened, somewhat incurved, often more or less toothed on the back, 

 2-3 mm. long, about twice as long as the style. 



In ponds and quiet streams, rare in our limits. 



38. NAJAS. 



Submersed aquatic herbs with slender branching stems; 

 leaves numerous, short, opposite or in threes, linear; flowers 

 monoecious or dioecious, solitary axillary, the staminate en- 

 closed in a membranaceous sheath; stamen 1; carpel 1, with a 

 short style and a 1-celled 1-ovuled ovary. 



Najas flexilis (Willd.) Rostk. & Schmidt. Stems slender; leaves numerousi 

 linear, acute or acuminate, 1-2 cm. long, minutely serrulate, the sheath broadly- 

 oblong; fruit 3 mm. long, oblong-linear, tipped with the persistent style; seed 

 pale-brown, shining. 



In lakes and slow streams, common and widely spread. 



39. LILAEA. 



Marsh or freshwater grass-like plant with fibrous roots; 

 leaves alternate; flowers monoecious, naked, in separate spikes 

 or intermixed; staminate floret a solitary nearly sessile 2-celled 

 anther subtended by a distinct bract; pistillate florets consisting 

 of naked sessile ovaries; styles short in the upper florets, elongated 

 in the lower ones; stigma cuspidate; ovule solitary. 



Lilaea subulata HBK. (Heterostylus gramineus Hook.) Leaves grass- 

 like, 15-30 cm. long, 2-4 mm. broad, thin; peduncles shorter than the leaves; 

 spikes crowded; spathe boat-shaped at base; styles of the lower flowers long 

 and filiform, gradually reduced upwards; akenes elliptical, acute, wing- 

 margined; lower ones largest and with a lateral tooth on each side at the base of 

 the style. 



In ponds, rare. Sumas River, Vancouver Island, Macoun; Oregon, Scouler, 

 Howell. 



40. ZOSTERA. 



Submersed marine perennial herbs with creeping and rooting 

 stems or rootstocks; leaves alternate, entire, ribbon-shaped; 

 flowers monoecious; perianth none; flowers of single stamens 

 and ovaries alternately in rows on a leaf-like spadix enclosed in 

 the membranous base of a leaf. 



Zostera marina L. Eel-grass. Leaves tape-like, obscurely 3-7-nerved, 

 50-100 cm. long. 



Very common along the seashore just at low tide mark but very seldom 

 flowering. There are perhaps two species on our coast. 



41. PHYLLOSPADIX. 



Perennial submersed marine herbs with thick rootstocks and 

 slender stems; leaves elongated, linear; flowers dioecious; per- 

 ianth none; staminate flower a single sessile 1-celled anther; 



