16 
The Philippine Journal of Science 
191S 
The growth of the plants in this experiment for a period of 
thirty days from the fifth of January to the fourth of Februarj^ 
is given in Table VIII. 
w 
Table VIII. — Growth of Elodea in jars with soil 30 days. 
No. of plant. 
Growth— 
, 
\ 
2 
8 
4 
5. 
6. 
7. 
8. 
9- 
10, 
Rooted in 
soil. 
Total ,__ 
Average 
Cm. 
10.6 
7.3 
7.1 
7.5 
8.0 
10.6 
8.2 
8.3 
6.4 
7.1 
Floating: 
over soil. 
With 
roots. 
Floatinar 
over soil. 
Without 
roots. 
81.1 
8.1 
Cm. 
5.9 
7.4 
7.1 
7,8 
5.7 
6.1 
7.1 
6.2 
7.4 
6.3 
66.0 
e.6 
Cm, 
5.4 
7.8 
5.0 
6.9 
6.2 
6.8 
6.4 
6.1 
7.2 
5.6 
63.4 
6.3 
An examination of Table VIII shows that there was little 
difference between the grovrth of the floating plants with and 
without roots. This would seem to indicate that roots are of 
no advantage to Elodea if they are growing in the same solution 
in which the plants are floating. 
The growth of the rooted plants was considerably greater than 
that of the floating ones. This could be explained readily on the 
ground already mentioned, and so these plants afford no evidence 
as to whether or not the roots are of advantage to Elodea as 
absorbing organs. 
In order to test the value of roots as absorbing organs it 
seemed necessary to find a soil which contained nutrient salts 
but little or no organic matter. These requirements seemed to 
be met by a soil found at the base of a granite cliflf and formed 
by the disintegration of the granite. Much of this soil had been 
weathered to the consistency of clay. For comparison with this 
soil clean washed quartz sand of a high degree of purity was also 
used as a substratum. 
On the 5th of April a series of four three-liter jars was pre- 
pared. A layer of soil 4 cm deep was placed over the bottoms 
of two and a similar layer of sand in the other two Ten 
plants 10 cm in length were then put in each jar. The plants 
m one jar containing soil and in one containing sand were held 
