WATER IN PLANTS. 87 



'2. Compare all the leaves which can be 

 obtained and note the arrangement of their 

 veins, whether netted or parallel. Examine the 

 stems of the same plants and see whether, as 

 a general rule, you find stems with dicotyle- 

 donous structure bearing leaves with netted 

 veins, and monocotyledonous stems parallel- 

 veined leaves. 



3. Take leaves of vanilla, 4 needle ' and 

 4 dagger ' plants, and pull off a portion of the 

 outside layer of the leaf (this layer is very 

 thin and care is required, but if the operation 

 is properly done no green tissue will come 

 away). Note that the outer skin is colourless, 

 that the underlying tissue is dark green and 

 soft, and has a number of hard fibrous struc- 

 tures, the veins running through it. 



WATER IN PLANTS. 



1. Pick a number of shoots of any ordi- 

 nary thin-leaved plant, such as a coleus. 

 Place some in water and leave others lying on 

 the table. The latter 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 



