SHADE TREES. 139 



attention to the specific requirements of the different species of shade 

 trees, particularly as regards soil conditions. Species which cannot tol- 

 erate drought or the slightest soil desiccation should never be planted in 

 sandy or gravelly soils possessing little water-retaining capacity; hence 

 care should be taken in dry situations in eliminating those species which 

 naturally grow in wet places. Neither should species that are adapted 

 to dry soil be planted in wet places. The more extensive use of loam or 

 soil containing a considerable amount of organic matter is needed in tree 

 planting. 



In conclusion it may be stated that the problems associated with tree 

 planting during the last decade do not constitute a reliable criterion of 

 the specific value of any species, since the same combination of conditions 

 is not likely to occur in a century. We believe, therefore, that any one 

 is justified in planting the much condemned elm, at least in country 

 towns, where atmospheric conditions are much more favorable than in 

 cities, and where the leopard moth is not so destructive. 



Rapidity of Growth of Trees. 



The variation in the growth of trees, due to the influence of many dif- 

 ferent factors, is quite marked, and even when trees of the same age are 

 growing side by side great difference in the size and development are 

 noticeable. A chestnut tree under certain conditions will attain a diameter 

 of 3 feet in fifty-six years, while another may require one hundred and 

 fifty years to reach a diameter of 18 inches. The average diameter of 20 

 white ash trees measured by us was 16 inches in twenty years; and Italian 

 poplars will occasionally grow 26 inches in the same length of time. The 

 Carohna poplar will reach a diameter of 30 inches in fifteen years, which 

 almost equals the growth of the eucalyptus in California. We have 

 observed pin oaks that grew 18 inches in diameter in twenty years. The 

 average diameter of 16 elm trees thirty years old was 17 inches. In 

 another instance a similar number of elm trees attained an average diam- 

 eter of 20 inches 4 feet from the ground in forty years. Recent measure- 

 ments have shown that the average diameter growth of the tliirty-year- 

 old elm trees for a period of seven years was 6 inches, wliile that of the 

 forty-year-old trees during the same period was 4| inches. It is not un- 

 common to find elms that have grown 3 feet in diameter in fifty years, or 

 4 feet in seventy years. An elm one hundred and thirty-one years old had 

 a height of 110 feet, and a diameter of 6 feet at the base. On the other 

 hand, many instances might be mentioned where trees have made very 

 slow growth. Some elms, for example, showed a growth of only 11 inches 

 in diameter in fifty years, and a white oak one hundred and thirty-two 

 years old reached a diameter of 16 inches. Rock maples grow fairly 

 rapidly in good soils, but we know of instances in which they have made 

 only 6 or 8 inches growth in diameter in sixty years. Species accus- 

 tomed to swamps, such as the white cedar and black spruce, grow quite 



