134 



PRACTICAL COURSE IN BOTANY 



FiG.152.— Stem 

 of tulip tree : s, s, 

 scars left by stipular 

 scales ; /, I, leaf scars. 



the bud. These scars are sometimes very persistent, and 

 in the common fig and magnolia may often be traced on 

 stems six to eight years old. Do they furnish 

 any indication as to the relative age of the 

 different parts of the stem, like the bands of 

 scars on twigs of horse-chestnut and hickory ? 

 Give a reason for your answer. (Fig. 152.) 

 150. Different rates of growth. — Notice 

 the ver}^ great difference between branches 

 in this respect. Sometimes the main stem 

 will have lengthened from twenty to fifty 

 centimeters or more in a single season, while 

 some of the lateral ones will have grown 

 but an inch or two in four or five seasons. 

 One reason for this is because the terminal 

 bud, being on the great trunk line of sap 

 movement, gets a larger share of nourish- 

 ment than the others, and being stronger 

 and better developed to begin with., starts out in life with 

 better chances of success. 



Make a drawing of your specimen, showing all the points 

 brought out in the examination just made. Cut sections 

 above and below a set of bud scars and count the rings of 

 annual growth in each section. What is the age of each? 

 How does this agree with your calculation from the number 

 of scar clusters left by the bud scales ? 



151. Irregularities. — Take a larger bough of the same 

 kind that you hav(? been studying, and observe whether the 

 arrangement of branches on it corresponds with the arrange- 

 ment of buds on the twig. Did all the buds develop into 

 branches? Do those that did develop all correspond in size 

 and vigor? If all the buds developed, how many branches 

 would a tree produce every year? 



In the elm, linden, beech, hornbeam, hazelnut, willow, and 

 various other plants, the terminal bud always dies and the 

 one next in order takes its place, giving rise to the more or 



