20 AQUATIC PLANTS IN POND CULTURE. 
The water plantain (Alisma plantago-aquatica) is another border 
plant, being found about the edges of ponds in water only 4 to 6 inches 
deep, its leaves floating on the 
heavy that 
it will not 
float when 
cut loose 
from the 
# bottom. 
Fic. 24.—Water plantain (Alisma plantago- = 
aquatica). Found in shallow water or mud When a 
throughout North America. Also in Europe pon d 1s 
and Asia. (After Britton & Brown.) 
drawn it 
settles down like a blanket, entangling the young 
fish so that it must be picked over by hand in 
order to extricate them. Its objectionable char- 
acters, in fact, are so great that it is only by 
comparison and on negative grounds that its 
merits are admitted by the superintendent. 
A number of years ago the ponds at Wythe- 
ville were well stocked with curled-leaved pond- 
weed, waterweed, and limeweed, with a few 
water-lilies (Castalia odorata) scattered here 
and there; but water-lilies have increased from 
year to year until they have taken complete pos- 
session of several of the ponds. At present they 
are so dense as entirely to exclude the ight from 
the ponds, and in consequence all the submerged 
plants, including the Chara, have been killed, 
leaving nothing below the lily-pads for the pro- 
tection of the young fish. During the period 
when Chara was present in great abundance and 
surface. It is valuable for the 
same characters exhibited by 
the arrowhead. 
The Chara at this station is 
a large form with long, slen- 
der internodes, growing in 
all ponds whether they are 
fed by spring or creek water. 
It is an excellent food pro- 
ducer, but grows so densely 
that the fish can with difficulty 
get through it, and it is so 
Fia. 25.—Chara fragilis. 
(After Strasburger, 
Noll, “Schenck ic 
Schimper.) A com- 
mon form of Chara. 
was regarded as a nuisance and the lily a desirable plant, some of the 
bass ponds annually yielded an average of about 25,000 young fish 
