THE WALNUTS AND HICKORIES 69 



persistent husk — the other and less well known genera have de- 

 veloped more or less winged fruits with characteristic differences. 

 The leaves of all are what is known as pinnately compound, that 

 is they consist of two rows of leaflets regularly arranged on either 

 side of the leaf stalk. They are much Hke the leaves of the ash 

 but the two may be readily distinguished by being arranged on the 

 branches alternately, instead of opposite in pairs as in the ash. 

 There are numerous other details that enable the student to dis- 

 tinguish between the leaves of the different forms, and this is 

 fortunate because most fossil plants are represented by leaves in 

 the rocks. More rarely are fruits preserved as fossils, and only in 

 the most exceptional cases do we find flowers or other parts. 



THE HICKORIES 



The hickories are now referred to the genus Hicoria, proposed 

 in 1808 by that romantic naturaKst Rafinesque, although many 

 botanists, especially in the Old World, still use the name Carya 

 proposed by the naturahst Nuttall in 1818 and almost universally 

 used for the hickories until about twenty years ago when the 

 botanists formulated rules governing such matters and decided 

 that the names first proposed should be the ones recognized. 



The hickories occupy a unique economic position, for although 

 the consumption of their wood is less in quantity than that of some 

 of the other hardwoods such as white oak or yellow poplar, or of 

 the various coniferous woods like the cypress or pines, it shares 

 with the black walnut the distinction of being the most costly 

 American wood. Hickory wood, although not remarkable for 

 beauty of color or grain, will probably be the most difficult wood 

 to replace when the approaching shortage becomes more acute, 

 since it combines weight, hardness, stiffness, strength and tough- 

 ness to a degree that is unequalled among commercial woods. The 

 Forest Service estimated that the consumption of hickory for 

 lumber, and for such things as spokes, tool-handles, rims, shafts, 

 sucker rods, etc., amounted to nearly five hundred million board 

 feet during 1908, and this exclusive of the large amount used as 



