26 THE COMMERCIAL HICKORIES. 



and in the Cumberland Mountains grows also with red oak, yellow 

 poplar, basswood, buckeye, beech,, and sugar maple. 



In their soil and moisture requirements, beginning with those which 

 require least moisture, the hickories rank as follows: Pignut, mocker- 

 nut, shagbark, bitternut, big shellbark, nutmeg hickory, pecan, water 

 hickory. 



TOLERANCE. 



Most hickories require but little light in early life, and grow under 

 fairly dense shade. A peculiar feature of the tolerance of hickories 

 is the remarkable rapidity with which they recover from suppression. 

 After being suppressed for from sixty to eighty, or even one hundred 

 years, during which time they reach diameters of only a few inches, 

 they are able to respond to the stimulus of increased light and imme- 

 diately begin to expand their crowns and put on heavy layers of wood. 

 A tree which has been suppressed and is then freed by an opening in 

 the forest cover will often develop at a faster rate of growth than that 

 of a normal tree of the same size and diameter which has never been 

 suppressed. This capacity for enduring shade is so strong in pignut 

 and shagbark that the largest diameter increase may come at the age 

 of 150 or even 200 years. 



In short, big shellbark and pignut are only slightly less tolerant 

 than sugar maple and beech of those trees which grow in the central 

 hardwood belt. This tolerance is common to the whole genus, though 

 different species show varying degrees of tolerance ; the true hickories 

 are all more tolerant than the pecans. In the order of tolerance from 

 those which require least to those which require most light, they rank 

 as follows: Pignut, shagbark, big shellbark, mockernut, bitternut, 

 nutmeg hickory, pecan, water hickory. 



The great shade-enduring capacity of most of the hickories is of 

 the utmost importance to reproduction, for to this capacity is due the 

 ability of the tree to hold its own in the' forest. 



REPRODUCTION. 



Hickory is reproduced both by seed and by sprout. Seedling 

 r?production, even in the virgin forest and under dense shade, is 

 made possible by the great tolerance of the young trees. The nuts 

 are borne at irregular intervals, but good seed years come practically 

 every other year. Nuts are seldom borne by trees under 5 inches in 

 diameter. Thrifty hickories standing in the open will frequently bear 

 as many as 2 or even 3 bushels of shelled nuts in a year, and improved 

 varieties of pecans will bear 15 bushels. Only a small proportion of 

 the seed is left to germinate, however, because squirrels, mice, hogs, 

 and man eat great quantities of the nuts, especially of the sweet- 

 kerneled pecans and shagbarks. Squirrels especially are to be 

 reckoned with, not altogether as enemies, but as friends; although 



