
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 EKuro- 
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. 
perfoliatum or Perfoliate (clasping- 
leaved) Pondweed; P. compressus 
or Flat-stalked Pondweed; P. 
pectinatus or Fennel-leaved Pond- yy 
Ve 
weed; P. /ucens or Shining-leaved ee ea W7 Y 
Pondweed; and P. graming or Xp | 
Grass-leaved Pondweed. 
The Potamogetons are easily 
grown in basins and ponds and 
may thrive in the Aquarium, P. 
densus and P. perfoliatum being 
especially desirable, the handsome 
deep olive-green leaves of the 

FIG. 129. Floating Pondweed, Potamogeton natans with 
former and the clear pea-green blossom; and Broad-leaved Pondweed, Potamogeton densus. 
: Reduced one-third. 
leaves of the latter forming a fine 
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 
aquarium. 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 as C. lanceolata 
and others classing the shorter-leaved of the latter species C. crispus and 
202 
