38 STRUCTURE AND PHYSIOLOGY OF SEED PLANTS 



B. The large horseshoe-shaped scars and the number and posi- 

 tion of the dots on these scars. Compare a scar with the 

 base of a leafstalk furnished for the purpose. 



C. The ring of narrow scars around the stem in one or more 

 places, and the different appearance of the bark above and 

 below such a ring.'^ Compare these scars with those left 

 after removing the scales of a terminal bud. 



D. The buds at the upper margin of each leaf scar and the 

 strong terminal bud at the end of the twig. The dots on the 

 leaf scars mark the position of the ducts and wood cells in 

 the fibro-vascular bundles which run from the wood of the 

 branch through the leafstalk up into the leaf. 



E. The flower-bud scar, a concave impression to be found in 

 the angle produced by the forking of two twigs, which form, 

 with the branch from which they spring, a Y-shaped figure. 



¥. The place of origin of the twigs on the branch (on a branch 

 larger than the twig handed round for individual study); 

 make a separate sketch of this. 

 The portion of a stem which originally bore any pair of leaves 

 is a ?iode, and the portions between the nodes are internodes. 



Describe briefly in writing alongside the sketches any observed 

 facts which the drawings do not show. 



If your twig was a crooked, rough-barked, and slow-growing 

 one, exchange it for a smooth, vigorous one, and note the differ- 

 ences. Or if you sketched a quickly grown shoot, exchange for 

 one of the other kind. 



Questions. 1. How many inches did your twig grow during 

 the last summer ? How many during the summer before ? 

 How do you know ? How many years old is the whole twig 

 given you ? 

 2. How were the leaves arranged on the twig ? How many 

 leaves were there ? Were they all of the same size ? 



1 Maple, box elder, or lilac may be used, though they are not nearly as good. 

 Instead of poplar, as described in the next section, basswood, any kind of hickory, 

 butternut, black walnut, oak, or willow will do. The rings are especially well 

 shown by cherry, apple, pear, cottonwood, or aspen. 



