Stumps that were otherwise intact often had small central cavities an inch or more in diameter. For these it was necessary to estimate the numbers of missing rings in order to obtain a figure for the approximate total age of the tree at the time it was cut. Many of the logs and stumps were so much decayed that growth rings were no longer distinct, and on most there were a few rings that were not clearly defined. In the majority of instances the time of cutting could not be determined accurately, but it is known that there was little tree-cutting after 1934 on most parts of the area. Probably most of the stumps on the Reservation that were well enough preserved to provide counts were from 20 to 30 years old. Most of the counts of growth rings on chestnut oaks were obtained on a hillside adjoining the Reservation where the trees were cut in the early nineteen forties. Width of the annual growth rings reflects rapidity of growth in the tree and is determined, in part, by the amount of annual rainfall, especially in this region on the western edge of the deciduous forests where moisture is the chief limiting factor. Periods of drought or of unusually heavy rainfall may result in growth rings smaller or larger than average. Because the trees draw moisture from the deeper soil layer there is a lag in their response to precipitation, and a single year that is much wetter or much drier than those preceding or following it may not stand out clearly in the annual rings. In individual trees the effect of precipitation is often obscured by the effects of crowding and shading by competitors, injury or disease. None of the trees examined for growth rings reflected the annual precipitation accurately for long periods though some indication of known drought periods or of series of wet years were usually discernible. For 35 black oaks, chestnut oaks, and American elms, growth rings averaged 3.81 per inch of trunk diameter (according to size of the tree; 5.1 rings per inch in those trees 9 to 12 inches in diameter, 4.0 in those 13 to 15 inches, 3.6 in those 16 to 24 inches, and 2.8 in those of more than 24 inches). Data from a few complete counts and many incomplete counts indicate that in _Gleditsia triacanthos_ growth is much more rapid, with only 2 to 3 rings per inch of trunk diameter, whereas in _Juglans nigra_, _Celtis occidentalis_, _Carya ovata_, and _Fraxinus americana_ growth is much slower, with usually five or more growth rings per inch of trunk diameter. Individual trees deviate widely from the average for their species, and those in rich bottomland soil grow more rapidly than those in shallow soil of hilltops or those on rocky slopes. If such factors are taken into account the ages of trees may be estimated from the diameters of their trunks. In mature trees growth slows; age is likely to be underestimated rather than overestimated in those of exceptionally large size.