BIOLOGY OF HIGHEK SEED PLANTS 11 



2. The plan and development of the branches. Select the 

 terminal portion of a branch of a spruce or pine rep- 

 resenting three or four years of growth in length. 

 The spruce is best for this study, but a pine branch 

 may be used. 



a. The parts and their arrangement. 



(1) Are the leaves cyclic or spiral in their arrange- 

 ment ? This is most easily determined on naked 

 portions of the twigs by means of the leaf scars. 

 What is the number and position of the buds? 

 Is there a bud in the axil of each leaf, as in the 

 lilac ? Are the branches disposed like the buds on 

 the main axis? Are the smaller twigs arranged 

 like the main branches ? Is the relation between 

 leaves, buds, and branches the same as in the 

 lilac and the herbaceous plant studied ? 



b. Seasonal growth of buds and branches. 



(1) Determine the limits of each season's growth in 



length on the main axis and the lateral branches. 

 Is there a uniform number of buds which grow 

 each season to continue the central axis and to 

 produce lateral branches ? Are some branches 

 more vigorous than others ? Do the vigorous 

 lateral branches produce twigg and buds disposed 

 like those on the main central axis of the branch ? 

 Observe old branches of pine and spruce. What 

 becomes of the lateral branches produced each 

 season ? Do the leaves persist on the main axis 

 between the annual branches ? The clusters of 

 lateral annual branches in the pine and spruce 

 are called false whorh of branches. 



(2) Sketch the entire branch examined above, to illus- 



trate the points outlined under a and b. Illustrate 



