- GROWTH 133 
- The following experiments illustrate the conditions oe 
which growth takes place : 
Take some seeds, soak in cold water, and 
plant either in sawdust or cocoanut fibre. Leave 
for a few days. | 
Put some other seeds in boiling water and treat as above. 
After a few days the seeds soaked in cold 
water will be found germinating. Those put first 
in boiling water will show no signs of germination or of life ; 
they are, in fact, dead, having been killed by the boiling water. 
Growth is possible only when the plant is 
living. 
Take two again Water one (A) care- 
fully every day, but do not water the other (B). 
Result. A grows, B does not. 
Conclusion. Water is necessary for growth. 
Take two growing beans, suspend from corks 
of two jars (Fig. 12). Put a little water at 
the bottom of one jar (A), so that the roots are in moist air, 
whilst in jar B the water covers the cotyledons. 
The plant in jar A grows much faster than 
that in jar B. 
Plants grow best when exposed to free 
oxygen. This experiment also shows the 
necessity of a certain amount of water for a plant, and the 
disadvantage of overwatering ; it explains, too, why draining 
_ 1s necessary. 
Experiment £ 
Result. 
Conclusion. 
Experiment II. 
Experiment III. 
Result. 
Conclusion. 
Take two air-tight jars, to the cork of each 
of which a moist sponge on which cress seeds 
have been sowed is fastened. 
In the bottom of one jar there should be a little water, in 
the other pyrogallic acid, which takes the oxygen out of the air. 
The seeds will not grow in the jar with pyro- 
gallic acid. 
As pyrogallic acid has taken the oxygen out 
of the air in the jar, it is clear that oxygen. is 
necessary to growth. 
Experiment IV. 
Result. 
Conclusion. 
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