HOW PLANTS BREATHE | DBE 
empty bottle and thrust the lighted end of the taper 
into it. The flame is not extinguished. A. suffocating 
gas, carbon dioxid, was in the first jar. This gas is 
given off by the germinating peas. Being confined 
| in the jar, so much of it accumulated that it 
smothered the flame. 
Lime-water or baryta-water is a test for 
-, Ccarbon-dioxid gas. Make some 
= 1},), lume-water by dissolving lime in 
water and allowing it to settle. 





Baryta-water is even better. 
Make a saturated solution of barium 
hydrate. Filter; or allow it to settle, 
and then pour off the clear liquid. It 
should be kept corked when not in use. 



XY 
4 
yy 
Y 
ar 
i) 
arava 
aa ve). 

Sian Ove, 
eA 4 
£0 
heh 
JaTaF 
% 
CX XS 
Take some in a shallow vessel. Open 
ave 
aaeras! 
(c -4- 
— 
ise = OX 
@ 
i 
the jar containing the germinating peas 
AY 
2: 
) 
(c 

=, 
4 
J 
K hed 
re 



e eae 






A 
re 

 B 
e, 
x ~ fu ) 
® 
* 
and pour from it some of the carbon- 
ih 
pti 
dioxid gas into the baryta-water. (The 
Fig. 157. The light . . ° = . 
is smothered in Carbon-dioxid gas is heavier than air and 
the gas given off : 
by germinating therefore flows downward when the Jar 
po is tipped.) Cover the jar again. Imme- 
diately on pouring the carbon dioxid mto the baryta- 
water, a white substance’ is formed. Chemists tell us 
1 Barium carbonate, if baryta-water is used, or calcium carbonate, 
if lime-water is used. Lime-water is easier to obtain, but the results 
are not so striking as with baryta-water. To make lime-water, take 
