12 
The Philippine Journal of Science 
1913 
On the fifth of April a series of four 3-liter jars were filled 
with the different strengths and another jar with tap water. 
Ten plants, 10 cm long and without roots, were placed in each 
jar and CO^ passed through the jars as previously described. 
The solutions were changed every five days. The experiment 
had to be abandoned at the end of fifteen days as after this 
vigorous growths of algae appeared in some of the jars. The 
growth of the individual plants for fifteen days is given in 
Table V. 
Table V. — Growth of Elodea in tap water and Knopfs 
solution, April 5 to 20, 
No. of plant. 
Growth in- 
Tap 
water. 
1 
2 
S. 
4. 
S. 
«. 
7. 
8 
9 
10 
0.5 
standard, standard, standard. Istandard 
Total — , 
Average 
Cm. 
9.2 
9.4 
8.8 
8.3 
7.0 
7.8 
7.4 
9.4 
9.7 
6.7 
Cm. 
9.5 
13.2 
11.0 
11.2 
11.6 
11.7 
8.3 
12.6 
10.4 
11.9 
Cm. 
12.3 
13.2 
10.2 
12.7 
10.5 
12.6 
12.7 
13.0 
7.8 
9.1 
83.7 
8.3 
111.4 
ILl 
114. 
11.4 
Cm. 
12.2 
12.0 
13.7 
15.4 
12.4 
9.9 
14.9 
10.6 
9.1 
11.8 
121.9 
12.2 
Cm. 
12.1 
14.2 
9.1 
11.9 
11.8 
11.6 
IS. 6 
11.6 
13.4 
10.9 
120.1 
12.0 
The greatest growth shown in Table V was made by the plants 
in twice the full strength of the standard solution. This growth 
was 48.2 per cent greater than that shown by the plants in tap 
water, but only 9.9 per cent greater than the smallest average 
growth made by any of the plants in the jars of Knop's solution. 
The difference between the plants in tap water and those in 
Knopfs solution were considerable, but small when compared with 
those produced by variations in the amount of CO2 in the water. 
The slight differences between the plants in the various jars of 
Knop's solution as compared with the greater differences between 
all of these plants and those in tap water would suggest that 
the Knop's solution added one or more elements in which the tap 
water was deficient but that wide variations in the concentration 
of Knop's solution produced only slight changes. This is in 
harmony with the similarity of the plants in previous experi- 
ments in tap water and in tap water diluted with an equal volume 
of distilled water. 
