3.20 SUMMER FLOWERS. 



linear, obtuse, waved and sinuated on their edges ; spikes 

 small. Ponds, streams and ditches. Fl. June. 



P. pusillus : aquatic ; stems thread-like ; leaves narrow- 

 linear, 1-3 inches long, not dilated at the base into a scarious 

 sheath ; spike short, close. Pools and still waters. Fl. June, 

 July. 



P. pectinatus : aquatic; stems thread-like; leaves narrow 

 linear, 2-3 inches long, dilated at the base into a rather long 

 sheath, scarious at the edge ; spike slender, interrupted. 

 Pools and still waters. Fl. June, July. 



ft Leaves opposite. 



P. densus : leaves short, ranged in two rows on opposite 

 sides of the stem, submerged, thin, broadly lanceolate, folded 

 and clasping the stem at their base ; spikes 2-4-flowered, be- 

 coming reflexed. Shallow pools and ditches. Fl. June, July. 



(273) Zannichellia. HORNED PONDWEED. 



Z. palustris : aquatic ; stems slender, branched, floating ; 

 leaves finely linear, mostly opposite, with a small, sheathing, 

 membranous stipule ; flowers axillary, sessile or nearly so. 

 Ponds or lagoons of fresh or brackish water. Fl. June to 

 August. 



(274) Stratiotes. WATER SOLDIER. 



S. aloides : aquatic ; leaves tufted at the bottom of the 

 water, sessile, long, narrow, succulent, bordered by small 

 pointed teeth ; flower-bracts with delicate dioecious peduncles, 

 bearing a spathe of two bracts, which enclose several stalked 

 male flowers with twelve or more stamens, and one solitary 

 sessile female. The plant rises to the surface to flower and 



