HOW PLANTS GIVE OFF WATER 103 
Can the roots take the water into the plant faster 
than the leaves can give it off? Here is a pretty experi- 
ment to show the power of root absorption. Young 
wheat plants growing in 
a pot will show it clearly 
if the pot 1s covered with 
a glass jar and the roots 
are kept warm. fig. 138 
shows how this can be 
done. If it is not sum- 
mer time, when the soil 
in the pot would be quite 
warm enough, the pot 
may be set in a_ broad 
pan of wet moss or saw- 
dust, and here covered 
with the glass jar. <A 
flame from a spirit lamp 
may be set so that it will 
warm the edge of the pan, 
but the soil in the pot 
must not be allowed to 


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Fic. 138. The roots are lifting more water 
into the plant than can be given off in 
the form of water vapour, so it is pressed 
out in drops. | 
get hot. In a few hours or a day the leaves will 
appear beaded with the drops of water which are 
pressed out. There are little holes on the edge of 
the leaf through which the water escapes. ‘T'hese are 
water stomates. 
