HISTORY OF THE LINDEN AND ASH 171 



and Germany. In this country our white ash, Fraxinus ameri- 

 cana, is found in the early Pleistocene of western Kentucky and 

 the late Pleistocene of Maryland; the existing blue ash (Fraxinus 

 quadrangulatd) of the Mississippi valley was present and pushed 

 northward as far as the Don Valley in Canada during an Inter- 

 glacial period when the climate for a tune was somewhat warmer 

 than it is at the present time in the same latitude. 



THE LINDEN 



The family Tiliaceae to which the Linden belongs comprises 

 about 35 genera and upwards of 400 existing species. These are 

 chiefly tropical, and they are massed in two general regions — 

 one around the Indian Ocean and the other in northern South 

 America. The number of genera that have known fossil repre- 

 sentatives is unfortunately limited to ancestral forms of the 

 linden (Tilia), to the genus Grewiopsis which is ancestral to the 

 existing oriental species of Grewia, to Apeihopsis which is ances- 

 tral to the South American genus Apeiba, and to the South 

 American genus Luhea. All of these indicate that in former times 

 the geographical distribution of the various members of this 

 family was very different from what it is at the present time. 



The genus Tilia, which gives its name to the family, although 

 belonging to a family that is essentially tropical, is itself confined 

 to the North Temperate Zone, occurring on all of the great north- 

 ern land masses, but now absent in western North America, in 

 central Asia, and in the Himalayan region. All of the existing 

 species are trees, all have similar simple alternate leaves with 

 free stipules, all have similar flower clusters borne on a large 

 leaf-like bract, and the fruits are nut-like, although some of the 

 members of the family have capsular fruits. 



The wood is pale in color and soft, but straight grained and 

 easily worked. In America it is commonly known as white- 

 wood, although the terms basswood and linn are also frequently 

 applied to it. Pulp mills consume large amounts of timber 

 annually and the lumber enters very largely into interior finish 

 and planing mill products, cheap furniture, turnery and similar 

 uses. 



