HOW THE LIVING PLANT USES WATER 85 
water, is limp. You see when it is covered with the 
outside strips, as it 1s when undisturbed, the outside 
part 1s pulling to shorten the stalk and the centre is 
pushing to lengthen it. This lengthwise pull between 
the inside and outside parts makes the stalk firm. 
Why the dandelion stem curls. Did you ever break. 
off a dandelion stem, press one end against your tongue, 
and make it coil up into beautiful curls as it splits? 
Do you know why. it does so? Even when you split 



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Fig. 121. Strip from dandelion stem in water, at left it gradually coils up, 
in salt water at right it uncoils. 
a stem with a knife or with your fingers it will curl 
a little. The inside part is trying to lengthen, and the 
outside part is trying to shorten. So when it is split 
it curls around toward the outside part. 
Split a stem and place it in a vessel of fresh water. — 
Watch it. It begins to curl more and more and more, 
until it makes a very close coil of several rmgs. The 
life substance in the tiny cells takes in more water and swells 
so, that all together they push harder than they did before. 
To prove this, put the strips from the dandelion stem 
in salt water. They begin to uncoil and finally become 
