86 



NATURE TEACHING 



soon droop and become limp. Now place some of these 

 in water, first cutting a little off the end of the stem to 

 make a fresh surface, and notice that, after a time, they 

 become stiff and fresh again, whilst those left on the 

 table steadily become more limp and at length wither 

 and dry up. Treat in the same way, for comparison, 



some thick leaves, such as 

 house-leek, sea -rocket, sea- 

 purslane, etc., and small- 

 leaved plants such as heather, 

 furze, broom, etc., and notice 

 that these take a very long 

 time before they show any 

 signs of drying up, indicating 

 of what use to these plants, 

 which can grow in places 

 where they get very little 

 water, their thick or small 

 leaves are. 



To prove more directly 

 that it is the leaves which 

 FIG. 8. Experiment to prove that actually give off water, take 



leaves give off water. ... 



a test -tube provided with a 



well-fitting cork. Split the cork lengthwise, and fit the 

 pieces on either side of a straight leaf, such as wheat or 

 daffodil (without cutting off the leaf or injuring it in any 

 way), and put the cork back so that the leaf is inside the 

 tube as shown in Fig. 8. Let the leaf remain on the 

 plant, and notice that the glass inside the test-tube first 

 becomes dimmed, and that later drops of water trickle 

 down and collect at the bottom of the tube. It is not 



