166 APPLIED BIOLOGY 



fact by pollarding willow trees and thus causing them to 

 produce from adventitious buds the straight and slender 

 branches suitable for making baskets. Some trees are 

 pollarded in order to get ornamental trees with rounded 

 bushy tops. There are many trees and shrubs which have 

 more than one bud in the axil of each leaf ; but only one of 

 these is axillary, while the others are supernumerary or 

 accessory. This is well shown in the box-elder and butternut. 

 On currant bushes there are usually three buds at the end of 

 each twig, the central one being the terminal bud and the 

 other two accessory. 



Opposite Branching. When the buds are in pairs at each 

 node and opposite each other, there is a four-rowed arrange- 

 ment on the twig ; but owing to the failure of some of the 

 buds to develop and the death of some young twigs, this 

 arrangement is seldom perfect on fully grown branches. 

 As examples, observe maple, ash, horse-chestnut, and lilac. 



Alternate Branching. When the buds are arranged one to 

 each node, there may be two, three, five, or more rows. In 

 passing from any bud to the next above on the stem we go 

 spirally around the stem. Examples are hickory, elm, beech, 

 ailanthus, and walnut. Alternate is more common than 

 opposite branching. 



159. Tree Forms. If the terminal bud takes the lead 

 in growth, the result is a tnee like the spruce or hemlock, in 

 which the straight main trunk can be traced to the very top 

 of the tree, and with relatively small lateral branches. When 

 the branches from the lateral buds develop rapidly, the result 

 is a round top tree, like the apple, in which the main trunk 

 cannot be distinguished from main branches. Most of 

 our common forest trees are intermediate between these two 

 types. Observe various trees and decide to which of these 

 classes they belong. Also notice that the characteristic 

 contour of a tree or shrub depends both upon its mode of 

 branching and upon the angle which the branch makes 



