16 NATURE STUDY REVIEW [9:1— Jan., 1913 



Sour Cherry and in like manner the Pear from the Apple. It is 

 these habit differences that form the most ready means of separat- 

 ing the contrasted trees just mentioned which may closely re- 

 semble each other in twig characters. The angle which the 

 branches make with the trunk is frequently a diagnostic character 

 of considerable value. For example, the ascending and grace- 

 fully outward curving limbs of the American White Elm stand 

 in contrast with the sharply divergent limbs of the English Elm. 

 Likewise the horizontal branches of the Tupelo and the strongly 

 pendant lower limbs of the Swamp White Oak are characteristic 

 of these species. The relative thickness of the branchlets con- 

 trasted in the Sweet Cherry and the Black Birch and the arrange- 

 ment of the branchlets whether opposite or alternate and whether 

 erect or drooping, may further be mentioned as habit characters. 



The method of branching and other features included in the 

 habit do not furnish such precise marks as do the twigs, and 

 cannot, therefore, be of much value in a descriptive key. In 

 fact, the habit varies considerably among individual trees of the 

 same species, no two trees having exactly the same method of 

 branching. Moreover trees grown in woods in company with 

 other trees are prevented by lateral shading from developing 

 their normal form and produce tall trunks with but little branch- 

 ing. The age of the tree is also an important factor in the out- 

 line, young specimens being in general narrower and more coni- 

 cal than in later life while those in old age may have lost shape 

 through ice storms, high winds and the attacks of fungi. Trees 

 grown in the open, however, despite the vicissitudes to which they 

 may be subjected, tend to assume a characteristic appearance. 



As one becomes more familiar with trees in their winter 

 aspect, the number that cannot be recognized at a distance be- 

 comes greatly diminished. We come to know trees by hardly 

 definable traits, much as we recognize our friends at a distance 

 by some peculiarity of form or gait. Watching the trees from a 

 car window is a great help in acquiring this familiarity with the 

 habit characters. 



Bark — Although it is upon the appearance of the bark more 

 than upon any other character that the woodsman depends in his 

 recognition of timber trees, the bark shares with the habit the 

 misfortune of being difficult of precise description. A study of 

 photographs, however, in connection with descriptions of the 

 color and texture will enable one to recognize a large proportion 

 of our trees by the appearance of the bark alone. 



