AQUATIC PLANTS IN POND CULTURE. 23 
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 Chara 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 stations, 
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, 
FiGg. 28.—Various-leaved water 
milfoil (Myriophyllum hetero- 
phyllum). Found in ponds, 
Ontario and New York to 
Florida, Texas, and Mexico. 
(After Britton & Brown.) 
few plants being objectionable in themselves for any reason other 
than growth which is overabundant or overpersistent. 
rie 
Fig. 29.—Cattail (Typha latifolia). Found 
in marshes throughout North America, 
except in extreme north. Also in Europe 
and Asia. (After Britton & Brown.) 
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 
where 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. Raymond H. 
Pond? shows by experiment that 
Vallisneria spiralis, Ranunculus 
aquatilis tricophyllus, Elodea 
canadensis, Myriophyllum spica- 
tum, Potamogeton obtusifolius, 
and Potamogeton perfoliatus, 
hence probably all rooted aquat- 
ics, are for optimum growth dependent upon their rooting in 
the substratum, and his conclusions are abundantly confirmed by 
+ 
@ Dwight Lydell in ‘‘ Transactions of the American Fisheries Society for 1905,” p. 193. 
+Report U. 8. Fish Commission 1903 (1905), p. 483-526. 
