322 NEW ENGLAND TREES IN WINTER. 



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. 423), 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. 515) 

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

 Poplars (fig. 5). Some few trees have their pith separated by 

 hollow chambers such as the Hackberry and the Butternut 

 (fig. 6) 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 scars at a node as in the Horse-chestnut, or alternate with only 

 one scar at the node as in the majority of species. Alternate leaf- 

 scars may be arranged along the twig in two longitudinal rows 

 when they are said to be 2-ranked, as in the Mulberry (fig. 8), 

 or in several rows when they are more than 2-ranked as in the 

 Poplars (fig. 5). Twigs sometimes if rapidly grown have the 

 leaf -scars which are normally opposite pulled apart to appear 

 alternate, but the typical condition will be found on other parts of 

 the tree. A few species like the Chestnut sometimes take the 

 2-ranked, and sometimes the more than 2-ranked position, and the 

 number of ranks in other forms, may be at times somewhat ob- 

 scured by a twisting of the twig. The distinctions in the main, 

 however, hold good and where a doubt is likely to occur in regard 

 to the arrangement, a place has been made in the key for the 

 species in both the 2-ranked and the more than 2-ranked groups. 



The size and shape of leaf-scars are important factors in identi- 

 fication. They may be very narrow as in the Pear and 

 their upper margins may be flat or convex as in the Black Ash 

 (p. 561) or deeply notched as in the White Ash (p. 557) 

 or form a band nearly surrounding the bud as in the Sycamore 

 (p. 483). They may become dingy and inconspicuous or be 

 sharply distinct by color contrast with the rest of the twig. Thus 

 the Elms and the Poplars have their leaf-scars covered with a 

 light-colored cork-like layer which makes them conspicuous 



