36 Trans. Acad. Sci. of St. Louis. 



in. It is very probable that some trees still standing are thus 

 affected, and in the years to come, when any " cyclone " 

 trees are felled, one ought to look for traces of the oedematous 

 wood. 



Many of the injured trees struggled along during the 

 summer of 1896, produced leaves in the spring of 1897, and 

 there seemed to be some chance that they might continue to 

 live. As the summer came on, however, another factor 

 entered into their environment which proved fatal to most of 

 them. The trees had a mass of foliage developed in the 

 spring which looked healthy and normal in every respect. 

 After several months of hot and dry weather the bark began 

 to break off in large sheets both from the trunks and branches, 

 particularly from the soft maples. The accompanying plate, 

 (VIII.) reproduced from photographs, shows several maples, 

 an elm and a honey locust from which the bark is breaking 

 away. It will be noted that these trees were not then dead, 

 as most of them had green leaves still on them (figs. 1-4). 

 I attribute this breaking away of the bark to powerful insola- 

 tion, causing what is known as bark scorching. Hartig* 

 defines the phenomenon of bark scorching (Rindenbrand) as 

 the drying and subsequent dying of the bark of smooth- 

 stemmed trees, which have been suddenly exposed to the 

 sun's rays. He says : •• It has been determined that death is 

 a result of intense heating brought about by direct insolation 

 in midsummer. " In another place t he discusses the conditions 

 existing in some spruce woods, in which the trees had been de- 

 foliated by the nun moth. " On Aug. 19th, the warmest day of 

 1892, when the thermometer registered at. 96. 8° F. in the shade 

 and 104.9° F. on a felled area that was not exposed to the 

 wind, it was found that on the southwest side of eighty-year- 

 old spruces, fully exposed to the sun, the temperature was 

 131° F. between the wood and the bark." The subject of the 

 temperature inside a tree, as compared with that of the air, 

 has been frequently considered. Some observers, such as 



* Hartig, R. Uber Sonnenbrand oder die Sonnenrisse der Waldbaume. 

 Unter3 a. d. forstbot. Inst. z. Miinchen. 1880. 



t Hartig, R. Diseases of Trees (translated by Somerville & Ward) 

 294-95. 1894. 



