84 NEW YORK STATE MUSEUM 



country. This is so generally recognized that an exhaustive dis- 

 cussion of the evidence seems entirely unnecessary. It should 

 suffice to note in passing, that most competent observers who have 

 studied the effects of petroleum upon trees, emphasize the vari- 

 ability of the results and attribute much of this to climatic condi- 

 tions prevailing at the time of spraying and for some days there- 

 after. 



Signs of injury by petroleum. Spraying dormant trees with 

 petroleum, pure or emulsified, may retard their development in the 

 spring. This may be comparatively slight and followed by en- 

 larged lenticels, a discoloration, death and cracking of the outer 

 layers of the bark and be accompanied the first season by abnor- 

 mally large, dark green leaves. The last has frequently been re- 

 garded as an evidence of benefit though it apparently results from 

 overstimulation and may be followed, if there be successive annual 

 treatments with oil, by smaller and eventually undersized pale 

 foliage. 



Applications followed shortly by adverse climatic conditions, 

 such as a severe winter or several humid days immediately after 

 spraying, may cause an extremely late starting of growth with 

 destruction of buds, limbs, or even large portions of the tree. 

 There is then apparently more penetration by the oil which, in 

 extreme cases, may kill the vital tissues to the sapwood or even 

 below. The inner bark turns dark brown, may remain sappy 

 under certain conditions for a considerable period and have a 

 sour or acid odor. Trees thus affected may have limbs girdled 

 near the middle with a dead inner bark and die gradually toward 

 each extremity, or dead branches may show a similar, well-marked, 

 girdled or dead area at the base, while badly affected limbs exhibit 

 localized injury to the inner bark on portions most exposed to the 

 spray or in connection with external rough places, which latter 

 greatly facilitate the absorption of oil. Young fruit trees may 

 have the bark badly blistered in the late spring and early summer, 

 the underlying tissues being soft and evidently unhealthy. The 

 death of affected trees or portions of the same may occur the 

 following spring, drag through the summer or be deferred for a 

 year or more. Even the buds fail to develop in some instances, 

 while in other cases the leaves may push out and attain a length 

 of half an inch or more before dying. In other cases the leaves 

 may attain full size and the tree succumb slowly in midsummer, the 

 extent and the rapidity of the withering probably being dependent 



