38 RELATION OF PLANTS TO MECHANICAL FORCES 



amine a second stem a week later and a third two weeks 

 later. 



Make a number of cuttings 01 some woody plant, such as Rosa, 

 Salix, Hibiscus, Populus, etc., and grow them in jars of water 

 or sand. Make an examination of the cut ends after two weeks, 

 and at similar intervals for some time to observe the development 

 of callus. Cut off branches of vigorously growing woody shoots 

 and note the formation of callus on the surface of the stumps. Ex- 

 amine the structures resulting from the differentiation of the callus. 1 



1 Sorauer- Weiss. Treatment of the Shoot. Popular Treatise on the Physiology 

 of Plants. 134. 1895. 



