138 STEMS 



Result? Why? Of what use to the potato is the skin? 



(a) Remove a ring of outer bark one inch wide from a 

 stem. (6) From another stem remove a similar ring, but 

 cut deeper, going through the bark to the wood. How do 

 the results in (a) differ from those in (6) ? Why ? 



Select any common woody-stem plant and with a sharp 

 knife cut from one side a wedge-shaped piece, cutting in 

 almost to the center. After some days examine the wound 

 and see how nature heals it. 



122. REPAIRING WOUNDS 



Object. To learn how a plant repairs injuries. 



Apparatus. Growing plants, a saw, and a knife. 



Method. Cut off a branch of a plant, and after several 

 days examine the cut-off end and notice how it has healed. 

 Compare woody with herbaceous stems in this respect. Go 

 into an orchard where branches have been removed in pre- 

 vious years. Notice how the tree has healed and is gradually 

 covering up the wound. 



If possible, cut a lengthwise section through the stump of 

 a branch which has been pruned and has partly healed over. 

 Where does the new tissue form in healing over an ampu- 

 tated limb? 



Conclusion. State how a tree repairs injuries and where 

 the new growth occurs. 



123. TURGOR 



Object. To show the effect of turgor on rigidity of 

 young plants which have no mechanical tissues. 



Method. Remove a young bean or pea plant which has 

 been grown in sawdust. Immerse it in water for a few 

 moments until it has become quite stiff. 



