94 THE NATURE AND WORK OF PLANTS 



120. Stems are made up of sections, or internodes. 



— If the stem of a mint or of the corn is examined, 

 it will be found that it exhibits a number of 

 " joints," indicated by external ridges which divide 

 it into a number of sections. Take two sections of 

 the stem not adjoining, and compare them. No dif- 

 ference will be found except in the matter of size 

 and age. The arrangement of the tissues is identi- 

 cal. Repetition of this test will show that a stem is 

 made up of a number of sections of the same struc- 

 ture. This characteristic is one which is not found 

 in any other member of the plant. 



121. Branches arise at the nodes or joints only. 



— The branches of roots were seen to arise at 

 any point on the main root. Leaves, branches, 

 and flowers are seen to be given off at the 

 nodes only of stems. Roots emerge from the ex- 

 treme lower end of the stem, or they may arise 

 from the lower nodes, as in the case of the stilt or 

 prop roots of the corn, or from any part of the stem 

 in climbing species. 



122. Relation of the leaves and tranches. — It 

 may be seen that buds or branches arise from the 

 stem immediately above the point at which a petiole 



