24 AQUATIC PLANTS IN POND CULTURE. 



observations in the ponds here described. His application of the 

 fact to fish culture, however, it would seem might be put differently. 

 While it is true that good soil is to be sought, it should be added 

 that for very rich soil it is important to avoid, if possible, plants 

 with a tendency to rankness. 



The quality of the w^ater is a factor which may entirely control 

 the conditions of fish culture. At Cold Springs, Ga., where the 

 water is soft, it is impossible to obtain a permanent growth of vegeta- 

 tion, and the ponds must accordingly be restocked from time to time. 

 Two species of Myriophyllum are the only plants that have been 

 successfully^ maintained through a season. It sometimes happens 

 also that even wnth exuberant vegetation there is a dearth of animal 

 life, and this might be ascribed to some property or deficiency of the 

 water, just as is the abundance of certain amphipods and other crus- 

 taceans which are an important food for young fish, these forms being 

 known to thrive and multiply best in water containing lime. 



A further quotation from Doctor Pond, in reference to Cerato- 

 phyllum^ is of interest in this connection. This nonrooted plant 

 he shows to be dependent primarily upon the nutrient salts in solution 

 in the water, and thus a competitor of many of the small forms of 

 life, which derive their sustenance from the same source. A pond 

 filled with Ceratophylhnn therefore would be expected to contain 

 less of these forms and, consequently, of the forms that live upon 

 them. From this it would seem to follow that the water best suited 

 to C eratophyllum would not contain sufficient food for young fish 

 if that plant were the predominant species, and if this reasoning 

 is correct the value of C eratophyllum, would depend uj)on the pres- 

 ence of sufficient rooted vegetation to offset the effects of competi- 

 tion. Such may have been the conditions at the Fish Lakes, where 

 there were an unusually large number of species of rooted plants, 

 above all of which, however, the superintendent believed Cera- 

 tophyllum the best. 



No particular species of aquatic plant can be said to be always de- 

 sirable. The endless interrelations of plant and animal life and 

 physical surroundings make the problem a special one for each locality. 

 It should be noted, however, that according to the data here presented 

 great caution should be used as to the introduction of the pondweeds, 

 waterweed, water clover, water-lilies, frogsbit, and cattail. The last 

 two can not be regarded as desirable in any fish pond. Chara^ in- 

 digenous at some stations, is in most cases so much in favor as a food 

 producer that notwithstanding its objectionable characters it is con- 

 sidered the best plant for fish-cultural purposes. It should be borne 

 in mind, however, that at the stations where this plant is a favorite 

 the ponds are of more recent construction than at Wythe ville, for in- 

 stance, where Ghara is especially troublesome. 



