120 ELEMENTARY BOTANY 
CHAPTER XVIII 
RELATION OF THE PLANT TO THE SOIL 
In estimating the relation of the plant to the soil the follow: 
ing experiments may be performed : 
Weigh ten cress seeds, Compare with their 
weight that of ten seedlings which have been 
grown from similar seeds in moist earth for a week. 
Result. | The seedlings weigh more than the seeds. 
The increase in weight may be due to the fact 
that the seedling has obtained something from the 
soil, or from the air, or from both the soil and the air. 
The next experiment is more difficult, and involves the use 
of a good balance and a water-bath. It is inserted here, for 
if even the experiment cannot be repeated owing to the want 
of apparatus, it serves at any rate to show that plants grown 
in the light are heavier than those grown in the dark, other 
conditions being equal, and that therefore plants do get food 
from the air. 
Experiment I. 
: Conclusion. 
Weigh two quantities of mustard seed, say 
10 grammes. Let one set grow in moist air in 
the dark, the other set in exactly similar conditions, but in the 
light. After these have been growing for a week compare 
their growths. 
Those grown in the dark will be longer than those grown 
in the light, but more straggling, less healthy-looking. Now 
dry both sets in a water-bath, and after that weigh. 
It will be found that those grown in the dark 
weigh much less than those grown in the light. 
Plants grown in the light take in something 
from the air which plants grown in the dark 
do not take in. 
In the next chapter, when the relation of the ee to the 
- Experiment II. 
Result. 
Conclusion. 
