6 NEW YORK STATE MUSEUM 



the central part of the State and about Albany resulted in an ex- 

 planation of the damage. 



July was ushered in by about ten days of unusually hot weather, 

 following a considerable period of drought, with high temperatures 

 prevailing on some days. While the week of July 6th was a little 

 cooler, the drought continued, and in fact the precipitation for the 

 entire summer was far below normal. On July 12th and 13th there 

 occurred a strong, hot and dry west and southwest wind, which 

 continued with greater or less strength for several days. 



The maple is well known as a very shallow rooted tree and the 

 effect of the dry wind upon transpiration in the leaves is very 

 marked in the case of any tree. It is apparent that the period of 

 drought preceding the early part of July had reduced the available 

 water of the soil to a minimum, so that the factors favoring trans- 

 piration (that is, dry, hot winds) which followed, greatly exceeded 

 the power of the trees to absorb water from the soil which was 

 actually deficient in moisture. Such a condition of affairs was 

 particularly active in the case of maples along streets, highways, 

 in parks or other situations where the soil was not protected from 

 drying out by litter or undergrowth. 



The leaves of the maple being unable to maintain the high rate of 

 transpiration necessary under such conditions, were susceptible to 

 the chemical activity of the sun's rays, causing the bronzing effect, 

 a chemical change of the cell contents, somewhat analogous to what 

 takes place normally in autumn when the leaves turn to shades of 

 red or yellow. In many cases this state was followed by withering 

 and death of the leaves, as sufficient moisture was not available to 

 revive the leaves and to maintain their turgidity, which alone keeps 

 them under ordinary conditions from collapsing. 



That the dry weather and dry winds mentioned were responsible 

 for the widespread damage seems probable also from the fact that 

 the trees in situations of permanently damp soil, as in deep wood- 

 lands, suffered little or not at all; and of the trees affected, the 

 greatest damage seems to have been on the side exposed most 

 directly to the wind. Elms, having deeper-going roots, did not 

 suffer so much as the maples, although considerable damage to their 

 foliage was noticed in the case of some trees growing in dry soils. 

 The leaves of the elm also possess a thicker epidermis and are 

 better adapted by structure to withstand the factors like wind and 

 heat which favor excessive transpiration and its subsequent damage. 



The injury to maple and elm foliage thus noted is not likely to 



