100 THE NATURE AND WOEE OF PLANTS 



The cornstalk is seen to be a cylindrical tower, 

 many storeys in height. Each storey is filled with 

 the cementing pith, and numerous braces run from 

 the ceiling to the floor of each in a method that 

 could not be improved by the best engineer. 



130. Mechanical tissues in a sunflower stem. 

 Repeat the above experiment with the stem of the 

 sunflower. Cut across a young stem and note the 

 position of the building elements. A few strands of 

 wood will be found arranged in a circle, and on the 

 outer side of each bundle of wood is a bundle of 

 bast. The centre of the stem is filled with pith. 



131. Mechanical tissues in a carnation stem. 

 Repeat the tests of strength with a carnation stem. 

 Cut a stem length- and cross-wise and note the 

 manner in which the material is arranged. The 

 bast will be found to form a circle, and immediately 

 attached to the inside of this circle is a second circle 

 of wood. The centre is filled with pith. This stem 

 is then like a tower made of two strong tubes 

 fastened together, and the centre is filled with the 

 cementing pith, which is also living and which be- 

 comes firm and bracing by the absorption of water. 

 Examine the stem of a mint in the same manner. 



