220 THE RESPIRATION OF ROOTS, 
side holes was furnished ssi a She tag and the other with a mer- 
curial manometer and a thermom the lower hole was ate pro- 
vided with a stop-cock, a was in ees eakien with a water cistern ; * 
by means of the two stop-cocks the air could be either expelled from, or 
f the above-sketched apparatus be left alone for some days, the 
manometer indicates diminution of pressure in the interior of the 
test-tube not referable to diminution of temperature or change in 
barometric pressure. The first result worth recording stands thus:— 
ud. cms. 
Total cae of gas collected ; ; 135°2 
Carbonic Acid ; : 2°0 
Base. ; ‘ ‘ . . : 22°6 
Nitrogen. : : 110°6 
Which shows that 5°74 Pee cms. ae ae have been absorbed, and 
have only partially been replaced by Carbonic Acid. The amount of 
8 paper), 
really diffusion of this gas through the tissues of the plan 
Further experiments with a modified apparatus ave! 
b. cms, - cub, cms, 
Original amount of Oxygen . "25°78 
Final . 14:00 minus difference 11°78 
Original - Nitrogen . 97°20 
‘inal . 97°4 plus difference 20 
5 "Carbonic Acid . 6-30 plus difference 6:30 
In another experiment the gas lost 5°18 cub. ems. of Oxygen, and 
gained 1°79 cub. cms. of Carbonic Acid. 
Action of roots on an atmosphere of pure Oxygen.—A. Veronica was 
pads in the spperstos during eight da oe Rear anometer indicated 
t diminution of pressure, which became gradually less marked, 
33 Aiea a finally slightly ak. The analysis stood 
thus 
cub, cms. 
Amount of original Oxygen ‘ : : 22:1 
final Ca tae Acid. ; =) 1 
3? 2? . . 
» es at * a i 9 
Sh owing as before t (if there is no fg in the apparatus) 
Nitrogen has been Shae as well as Carbonic Acid. 
els “Ale Ace on an atmosphere deprived of Oxygen.—In these 
i : e first trial was with an atmosphere rich 
in prrectensd Acid G vol. CO,); after some ay nrg as the plant did not 
suffer, anat: reentirely composed of Carbonic acid was substituted, 
and under these cireumstances it died. Another Ivy plant was ex- 
osed to an atmosphere of pure. ace and the result obtained was 
as follows :— 
cub. cms. 
Amount Tey Nitro 21-1 
final Oxygen a Carbonic Acid. 15 
” » Nitrogen - 19°6 
rE ze 
* i 
