328 NEW ENGLAND TREES IN WINTER. 



the Ash are not covered by persistent bases of leaf-stalks and there 

 are 2 or more pairs of scales to the leaf buds, we therefore pass 

 to 14. The relatively small size of the buds and their freedom 

 from stickiness takes us to 15 where the number of the bundle- 

 scars and the other characters given show us that we have in hand 

 a twig of one of the Ashes. We now turn to No. 164 and confirm 

 our determination of the genus by reading the general description 

 of the Ashes. To find out which Ash we are dealing with we 

 precede with the key of the Ashes and, knowing that the leaf-scars 

 in our specimens are deeply concave on their upper margins, we 

 conclude that we have the White Ash (Fraxinus americana) . 

 At page 556 we find a detailed description with photographic 

 illustrations of this species and may learn the winter characters 

 of the tree not already given in the key. If the description and 

 photographs do not correspond to the tree under investigation, we 

 know that we have gone astray at some point in the key, and 

 turning back we repeat the analysis taking if need be the other 

 alternative of a pair where the choice had been doubtful. 



Sometimes a tree is variable in the characters used in the key. 

 Thus the Chestnut has terminal buds sometimes present on the twigs 

 though they are generally absent. In such cases, however, and 

 where there is a legitimate doubt as to whether the tree should be 

 placed in the first or the second group, it has generally been placed 

 in both so that either of the two choices should lead to the correct 

 name. The determination of the presence or absence of the ter- 

 minal bud is perhaps the greatest pitfall likely to be found in the 

 use of the key, but should give little difficulty if the discussion in 

 the introduction is understood and the terminal scar is looked for 

 with the aid of a hand-lens. 



