1-OND WEED TRIBE 



299 



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

 pistils alternately arranged in 2 rows in a long leaf dike sheath. 

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

 in form.) 



Pot 1 Natans 



(Floating Pond-w 



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 in 

 which it grows ; smooth, floating leaves, 

 on long stalks ; and cylindrical spikes of 

 small green flowers, which rise above the 

 surface of the water. The upper, or 

 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. perfoliatus (Perfoliate Pond-weed). Leaves alternate, all 

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

 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. /'. 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. pusillus (Small Pond-weed). Leaves 

 linear, very narrow ; flowers in along-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 

 Potamogeton Densds interesting family of plants, easy to obtain, 

 ^Oppositr-Uaved Pond weed) or pleasant to examine, it is not thought 

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