96 



THE VEGETATIVE ORGANS 



(and many fruits) provide similar examples, and in each 

 case we find that the waxy coating very effectually prevents 

 the surface from becoming wetted. Further modifications 

 will be noted in connexion with the habitats of plants. 



In the familiar process of wilting we have another good 

 illustration of transpiration. Take two shoots and place 

 the freshly-cut end of one in water, but allow the other 

 to lie on the table. Compare them in an hour. The one 

 in water is fresh and rigid, while that on the table has 

 become limp, i. e. the shoot cut off from its water-supply 



Fig. 57. Experiment to illustrate Turgidity. i, piece of 

 Daffodil stalk ; 2, cut into two strips ; 3, cut into four strips ; 

 4, the same in water. 



has wilted. Similarly, if a plant rooted in the soil be 

 insufficiently watered it wilts, i. e. its shoots and leaves 

 become limp and droop ; but such a plant soon regains 

 its freshness and turgidity on being watered. 



Turgidity. A simple experiment will help us to under- 

 stand this. Take a piece of the flower-stalk of the Dandelion 

 or Daffodil, about three inches long, and cut it down the 

 middle, as in Fig. 57, 2. Does any change in shape take place ? 

 Which is now the longer side ? the inner or the outer ? 

 The inner side being the convex and therefore the longer 

 side, in what condition were the tissues of this surface 

 before the stalk was cut ? Clearly they were compressed, 



