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 

 surface. It is valuable for the 

 same characters exhibited by 

 the arrowhead. 



The Chara at this station is 

 a large form Avith 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 

 heavy that 

 it will not 

 float when 

 cut loose 

 from the 

 bottom. 

 W hen a 

 pond is 

 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 light 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 

 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 



Fig. 24. — Water plantain (Alisma plantago- 

 aquatica). Found In shallow water or mud 

 throughout North America. Also in Europe 

 and Asia. (After Britton & Brown.) 



Fig. 25. — Chara fragilis. 

 (After Stras burger, 

 Noll, Schenck & 

 Schimper.) A com- 

 mon form of Chara. 



