AQUATIC PLANTS OF FRESHWATER 



at the base, and larger simple sparingly branched ovate floating leaves. 

 The peduncles of the fruit are as thick as the stems and the nutlets are 

 hard, pitted and with two groves on the back; the embrio forming an in- 

 complete circlet with its apex pointed to the base. Native in canals and 

 streams throughout North America, and flowers in July and August. 



Potamogeton densus (Linn.) or Close or Broad-leaved Pondweed, Fig. 

 129, has single or branching stems, broad olive-green submerged and float- 

 ing leaves fitted closely to the stem 

 and overlaying each other, having 

 sharply defined midribs. The fruit 

 is obvoid rounded and indistinctly 

 three-keeled and the embrio re- 

 curved or spiral. This is a Euro- 

 pean species which has become 

 naturalized in the United States. 



Other frequently occurring 

 species are: — P. fluitans or Long- 

 leaved Pondweed; P. heterophyllum 

 or Varied-leaved Pondweed; P. 

 ferfoliatum or Perfoliate (clasping- 

 leaved) Pondweed; P. compressus 

 or Flat-stalked Pondweed; P. 

 fectinatus or Fennel-leaved Pond- 

 weed; P. lucens or Shining-leaved 

 Pondweed; and P. gramina or 

 Grass-leaved Pondweed. 



The Potamogetons are easily 

 ■grown in basins and ponds and 

 may thrive in the Aquarium, P. 

 densus and P. ferfoliatum being 

 especially desirable, the handsome 

 deep olive-green leaves of the 



C J iU 1 '^^G. 129. Floating Pondweed, Poiamogeton natans with 



rormer and the clear pea-green blossom; and Broad-leaved Pondweed, PoMmo^«o« </«»™j. 



leaves of the latter forming a fine Reduced one-third. 



contrast with other aquarium plants. They should be planted in soil or 

 pond mud in shallow pots covered with pebbles in the corners of the 

 aquarmm. They are mainly propagated by cuttings, and in nature by 

 rhizomes and the peculiar winter buds which remain dormant in cold 

 weather and form new plants in the spring. Botanists are at variance in 

 naming two species of this plant; some designating C. crispus zs C. lanceolata 

 and others classing the shorter-leaved of the latter species C. crispus and 



