POND-WKED TRIBE 



299 



4. ZosTERA (Grass-wrack). — Flowers composed of stamens and 

 pistils alternately arranged in 2 rows in a long leaf-like sheath. 

 (Name from the Greek, zoster, a girdle, which the leaves resemble 

 in form.) 



POTAMOOETON NaTANS 



{floating Pond-weed) 



I. PoTAMOGETON (Pond-weed) 



1. P. natans (Floating Pond-weed). — Upper leaves elliptical, 

 ribbed, and cellular ; lower, submersed, linear. An aquatic 

 plant, with cord -like stems, propor- 

 tioned to the depth of the water m 

 which it grows ; smooth, floating leaver 

 on long stalks ; and cylindrical spikes nt 

 small green flowers, which rise above the 

 surface of the water. The upper, 01 

 floating leaves, are 2-3 inches in length 

 the lower, which are not always present 

 are very narrow, and a foot long or more. 

 Ponds and ditches ; common. — Fl. June 

 to August. Perennial. 



2. P. perfoliatiis (Perfoliate Pond-weed). — Leaves alternate, all 

 submersed, egg-shaped, embracing the stem, pellucid, 7-nerved. 

 Remarkable for its brown, almost transparent leaves, 2-3 inches 

 long, which when dry have the appearance of gold-beater's skin, 

 and are so sensitive of moisture that they will curl when laid on 

 the palm of the hand. Ponds and lakes ; common. — Fl. June to 

 August. Perennial. 



3. P. densus (Opposite-leaved Pond- weed). 

 — Leaves opposite, all submersed, embracing 

 the stem, pellucid. Like the last in habit, 

 but smaller. Ponds and rivers ; common. 

 — Fl. June to August. Perennial. 



4. P. fusillus (Small Pond- weed). — Leaves 

 linear, very narrow ; flowers in a long-stalked, 

 loose spike. A tangled mass of thread-like 

 stems, and dull, olive-green leaves, with 

 numerous spikes of brownish flowers, which 

 are either submersed, or partially rise above 

 the surface of the water. Ponds and lakes ; 

 common. — Fl. June to August. Perennial. 



From eighteen to twenty species of Pond- 

 weed are described as natives of Britain ; 

 they all, more or less, resemble the above 

 in habit, and as they are by no means an 

 PoTAMor.ETON Densus interesting family of plants, easy to obtain, 

 (Opposite^leaved Pond-weed) q,- pleasant to examine, it is not thought 



