Roots and its Influence on the Ecesis of Plants in Swamps . 23 
taken in the swamp bordering on Mud Lake. Part of the samples were 
taken in the Car ex- Calamagrostis associes, and the others in the Larix - 
Picea associes. All swamp samples were taken in areas in which Sphagnum 
and other mosses were abundant. A third series of samples was taken 
from Henderson’s bog, north of Lake Hubert. One sample was taken in 
the Carex associes and the other two below Sphagnum in the Chamae - 
daphne-Andromeda associes. The results are presented in the following 
table : 
Table III. 
Gas Content per Litre of Water fro7n Various Associes. 
Source. 
Sample 
N timber. 
Carbon 
Dioxide . 
Oxygen. 
Nitrogen. 
c.c. 
c.c. 
c.c. 
Hubert Lake 
1 
J-o 
7-6 
13-0 
>> 
2 
7*2 
I 2*6 
55 
3 
1-2 
7‘4 
— 
55 
4 
1*2 
7*6 
12-4 
55 
5 
1*2 
7-6 
— 
55 
6 
1*0 
7.8 
12-8 
Mud Lake : Carex -Calamagrostis 
1 
5*8 
3-2 
t6-8 
55 5 > 
2 
6*o 
3.0 
17-2 
5 5 5 5 
3 
6*o 
3 *° 
1 7 ” 2 
,, Larix- Picea 
1 
8-4 
2-8 
17-0 
Henderson’s bog : Carex 
1 
8-4 
4*6 
15*4 
,, Andromeda 
1 
9’8 
3-9 
1 i*i 
>> a 
2 
10*2 
3*8 
14-8 
The field analyses were made with the burette only, the solutions being 
introduced into the burette. Under the conditions the results are not as 
accurate as those made in the laboratory with pipettes. Comparison of the 
results, however, with analyses in the laboratory shows that the errors are 
not more than twice those of laboratory analyses, and accordingly they may 
be used in comparing results. 
It is to be noted from the figures here given that a marked difference 
exists between the air content of a lake and that of a swamp. Hubert is 
a spring-fed lake with cold water and a clean gravelly or sandy bottom. 
The bottom where the samples were taken was of very coarse gravel or 
pebbles. The water is well supplied with oxygen. When a lake becomes 
converted into a swamp, a very evident decrease of oxygen occurs with 
a marked increase in carbon dioxide content. The oxygen content falls off 
to half or less that of lake or tap water. This undoubtedly is a very 
important factor in retarding the growth and activity of roots of plants 
which do not have air-conducting systems. The sample from the Carex 
zone of Henderson’s bog was taken just at the edge where Carex was 
invading the Castalia associes. The oxygen content there is somewhat 
higher than it is in later stages. The high carbon dioxide content is to be 
explained by the decomposition of organic matter. Any lake which con- 
tains a large amount of vegetation is usually found to be low in oxygen and 
