82 The Great World's Farm 



water supplied to the roots will be sufficient to revive it. 

 Damp air will be of no use; neither will the heaviest dew 

 avail anything. The roots, and the roots only, can fur- 

 nish the necessary supply. 



Of course every substance — even, as we have seen, the 

 hardest rocks — will absorb some amount of water when 

 actually steeped in it; and so, if a withered shoot is kept 

 soaking in water, it will absorb a certain quantity in time, 

 as any piece of dead wood does. But leaves and stems 

 have little or no power of absorbing moisture from the air. 



This is the general rule, to which there are a few, but 

 only a few, exceptions; lichens, which have no roots, do 

 draw moisture from the air, and would be badly off if they 

 could not, considering the bare rocks upon which they 

 grow. Mosses, too, which grow where there is little or 

 no soil, also supply themselves with moisture from the air 

 to a great extent; and so it is believed do plants, such as 

 the mistletoe, which grow upon others. 



But still the general rule holds good; leaves have little 

 or no power of absorbing moisture either from the air or 

 from water poured upon them. 



And yet, how the drooping leaves revive on a dewy 

 evening, or in a shower of rain, or even under the influ- 

 ence of a shower from the watering-pot ! The water can- 

 not surely have had time to reach the roots, and then to 

 travel up the stem. 



Water certainly does travel upwards with amazing 

 rapidity in some plants, as will be seen presently; but 

 when leaves revive on a dewy evening, or during a shower, 

 it is not because they have drunk in any of these fresh 

 suppUes. Moisture is constantly passing up to them in 

 larger or smaller quantities from below; but they part 



