AQUATIC PLANTS IN POND CULTURE. 



23 



Fig. 28. — Various-leaved water 

 milfoil (llyrioiihylluin lietero- 

 phijUum). F'oiind in ponds, 

 Ontario and New Yorli to 

 Florida, Texas, and Mexico. 

 (After Britton & Brown.) 



is the principal plant, and it is quite satisfactory to the superintend- 

 ent as a food producer. At one time, he asserts, " The Potamogeton 

 drove Char a out and I could not raise 

 100 fish where before the Chara went I 

 could raise 1,000." « 



RESUME OF OBSERVATIONS. 



The various estimates of the commoner 

 plants as found at the different statit)ns, 

 together with the differences in condi- 

 tion and environment, make generaliza- 

 tion difficult. The foregoing observations 

 seem to show, however, first of all that 

 the fish-cultural value of a species is 

 chiefly a matter of the growth it attains. 

 Its merits, as food producer, shelter, and 

 oxygenator, are determined by the kind 

 and quantity of its foliage, stems, and 

 roots, and so likewise are its demerits, 

 few plants being objectionable in themselves for any reason other 

 than growth which is overabundant or overpersistent. 



The growth of plants, how- 

 ever, being a matter of environ- 

 ment, depends chiefly, in the case 

 of rooted species, upon the char- 

 acter of the bottom soil. Species 

 most desirable in one locality 

 may be obnoxious in another 

 wdiere by reason of the fertile 

 soil the growth becomes dense 

 and difficult to control. In his 

 paper entitled " The biological 

 relation of aquatic plants to the 

 substratum," Dr. Eaymond H. 

 Pond ^ shows by experiment that 

 Vallis7ie?'ia spiralis, Ranunculus 

 aquatilis tricopliyUus, Elodea 

 ca7iadensis, Myriophyllum spica- 

 tum, Potamogeton ohtusifolius^ 

 and Potamogeton perjoliatus, 

 hence probably all rooted aquat- 

 ics, are for optimum growth dependent upon their rooting in 

 the substratum, and his conclusions are abundantly confirmed by 



Fig. 29.— Cattail {TypJia latifolia). Found 

 in marshes throughout North America, 

 except in extreme north. Also in Europe 

 and Asia. (After Britton & Brown.) 



» Dwight Lydell in " Transactions of the American Fisheries Society for 1905," p. 193. 

 "Report U. S. Fish Commission 1903 (1905), p. 483-52G. 



