IDENTIFICATION OF TREES 187 



but these as well as other differences in the sculpturing are shown 

 in the photographs and do not require further discussion. 



Tivigs — The unqualified, word twig refers in the descriptions 

 to the growth of the past season only. Older twigs and branch- 

 lets are the designations employed for the small growth of several 

 seasons. The Horse-chestnut (fig. 20) has been taken as a con- 

 venient form to illustrate the various markings found on the twig 

 and is discussed on page 39. 



In some species, such as the Black Birch (p. 281) and the 

 cultivated Cherry (p. 3G9), a sharp distinction can be drawn 

 between rapidly-grown long shoots which have elongated inter- 

 nodes and continue the growth of the twig and slowly grown 

 short spurs which have greatly abbreviated internodes and crowded 

 leaf-scars. The fruit-spurs of the Apple (p. 353) and Pear 

 (p. 351) are of this latter type. 



Of the distinctive 'characters given under the heading twigs may 

 be mentioned the relative thickness, whether stout or slender, the 

 presence or absence of thorns or prickles, the color, the taste as 

 indicated under the discussion of the bark, and the character of 

 the surface, whether smooth or more or less covered with hairs. 

 Twigs are called hairy when the hairs are individually distinct, 

 downy when they are fine and numerous, and woolly or cottony 

 when they are twisted together into a more or less felt-like mass, 

 but these distinctions cannot be always sharply drawn. A twig 

 if smooth may be dull or shiny in appearance. The lenticels are of 

 most distinctive value in those forms like the Birches (p. 289), in 

 which they become horizontally elongated with age. The color, 

 size and shape of the pith are often characteristic as seen in the 

 wide salmon-colored pith of the Kentucky Coffee Tree (p. 381) 

 and the star-shaped pith in the Oaks and to a less degree in the 

 Poplars (fig. 100). The pith, however, frequently varies consider- 

 ably in color in a given species. Some few trees have their pith 

 separated by hollow chambers such as the Hackberry and the 

 Butternut (fig. 101) or have solid pith but with woody cross 

 partitions such as the Tupelo. 



Leaf -scars — The arrangement of the leaf-scars form primary 

 divisions in the classification. They may be opposite with two 



