STEMS AND BUDS 57 



must be practiced even before the buds appear in order to 

 condition the plant properly. This will be discussed in 

 Chapter 14. 



Nearly all leaves are opposite as in lilac or alternate as in 

 elm, but they may be spiral, i.e., on more than two sides. 

 The buds at the base of the leaves have the same arrange- 

 ment. The position of the buds determines largely the direc- 

 tion of branching and should be considered in pruning and 

 training as explained in the next chapter. Most plants have 

 a bud on the end of the stem, called terminal bud, which is 

 the most active in growth and tends to continue the growth 

 of the stem in the same direction. Side or lateral buds cause 

 branching when they grow. The elm twig has so weak a 

 terminal bud that the last or upper lateral bud usually grows, 

 but in Figure 13 the two last buds grew, making a branch on 

 twig C. 



Adventitious buds are those which grow at places other 

 than the axils of the leaves. They may appear on roots, 

 stems, or leaves, and they frequently develop after injuries, 

 such as the removal of a large branch or the topping of a 

 tree. A bud can grow only with dividing cells, but how a 

 plant can develop such cells at unusual places is not known. 



When the bud scales fall from a bud they leave individual 

 scars. The terminal bud scale scars are so evident that a 

 series of these marks are called a terminal bud scale scar, 

 which marks the extent of the year's growth. Two are shown 

 on twig D in the above figure, which indicates that the lower 

 end of the stem is three years old. 



Plants, such as spirea, which bear flowers on the current 

 growth of the stem may be heavily pruned in the early spring 

 to stimulate the growth of flowering wood. Other plants, 

 such as most fruits, which bear flowers on the previous year's 

 wood will have their potential flowers removed by spring 

 pruning. This may be desirable if they usually bear too 

 much fruit. 



