CARBONIC ACID BY LIVING PLANTS. 
617 
It therefore appears that during fourteen days the bark had evolved 269 cub. centims. 
of carbonic acid, or more than four times its own volume, under circumstances which 
preclude the absorption of oxygen. The Table also indicates a preponderance of the 
evolution during the day (a circumstance which other observations show in a marked 
manner). The amount exhaled during the day amounted to 143 cub. centims., that ex- 
haled during night 126 cub. centims. The small amounts of nitrogen are probably due 
to some of that gas being obstinately retained in the tissues of the bark. 
Other parts of various plants were submitted to the treatment described above, of 
exposure in eudiometers over mercury. In all cases gas was evolved. This gas did not 
consist, in most cases, wholly of carbonic acid, but contained nitrogen, though in far 
less amount. The residual gas, after the removal of the carbonic acid, was in several 
cases tested for oxide of carbon, and for marsh-gas ; but in no instance could a trace of 
either be detected. The following Table contains an account of many of the experi- 
ments of this nature. The gases are reduced to the usual standards, and corrected for 
aqueous vapour. 
Name and part of plant. 
Weight, 
in grms. 
1 
Weight, 
in grms., 
dried. 
Total 
gas, 
cub. 
centims. 
2: 
centims. 
N, cub. 
centims. 
C0 2 
from 
1 grm. 
nat. state. 
C0 2 
from 
1 grm. 
dry. 
Time of 
experi- 
ment. 
Bark of Cupressus Lusitanica 
5-00 
17-90 
15-00 
2-00 
3-00 
5 days; 
Leaf of Cinchona officinalis, cut in pieces 
0-84 
0-28 
0-68 
0-68 
0-80 
2-40 
5 „ 
Leaf of Cinchona officinalis , with petiole sealed 
1-30 
0-43 
0-90 
0-69 
2-07 
5 „ 
Leaf of Mahonia Leschenaultii 
0-65 
1-70 
1-31 
0-39 
2-01 
5 „ 
Wood of Cinchona officinalis 
500 
2-75 
1-20 
0-70 
0-50 
0-14 
0-25 
5 „ 
Twig with leaves of Cinchona officinalis, stalk 
sealed .. 
4-75 
1-50 
6-90 
6-62 
0-28 
1-39 
4-41 
4 „ 
Leaves of dwarf bamboo 
10-00 
3-25 
5*55 
4-83 
0-72 
0-48 
1-48 
5 „ 
Blades of Festuca ovina 
! io-oo 
2-68 
21-97 
19-51 
2-46 
1-95 
7*28 
3 „ 
Rhizome of Iris Germanica 
4-75 
1-13 
11-70 
11-10 
0-60 
2-33 
9-82 
3 „ 
Spadix of Richardia 
3-00 
0-50 
9-35 
8-75 
0-60 
2-91 
17*50 
3 „ 
Pseudo-bulb of an orchis 
5-25 
1-25 
1-60 
1-50 
0-10 
0-28 
1-20 
5 „ 
Rootlets of Acadia dealbata 
10-00 
2-00 
5-70 
5-00 
0-70 
0-50 
2-50 
5 „ 
Rootlets of Festuca avina 
io-oo ; 
2-75 
25-80 
24-60 
1-20 
2-46 
8-94 
5 „ 
Woody stems of Erica pubescens 
5-00 
2-50 
11-90 
11-30 
0-60 
2-26 
4-50 
3 „ 
Leaves of Erica pubescens 
5-00 
1-25 
7-90 
5-80 
2-10 
1-16 
4 64 
5 „ 
Leaves of Cupressus Lusitanica 
10-00 
4-75 
13-50 
12-60 
0-90 
1-26 
2-65 
3 „ 
Phyllodes of Eucalyptus globulus 
5-00 
2-50 
10-50 
8-90 
1-60 
1-78 
3-56 
5 „ 
Among a larger number of experiments, conducted with various portions of phanero- 
gamous plants, I have not found a case in which carbonic acid failed to be given off, in 
greater or less amount, when they were exposed in a tube over mercury. Even mosses 
and liverworts show the same reaction, though in many instances the quantity exhaled 
is but small. A plant of Jungermannia , however, gave off absolutely no gas for three 
days ; but at the end of that time a small quantity appeared. This was found to be 
carbonic acid. The probable reason why these lower orders of plants, rich as they are 
in chlorophyll, and in active growth, evolve in many cases a less amount of gas, is indi- 
cated in the general conclusions of this memoir. 
The actual amount of gas evolved from different plants or different parts of the same 
