von Schrenk — Trees of St. Louis as Influenced by Tornado. 33 



might be either that belonging to 1896 or 1897, and where the 

 outer ring was of peculiar structure, following a normal ring, 

 it was, as a rule, considered as being that formed after the 

 storm in 1896. 



The wood of the trunk was affected by the loss of leaves 

 and branches in a manner which was to have been expected. 

 A very much decreased rate of growth was very evident in 

 most cases, irrespective of the species. Some wood had been 

 formed before the storm and in many trees it seemed as if 

 this had been the last, for the outermost ring was very narrow 

 and followed a ring of the usual average width. In other 

 trees two narrow rings were found, outside a wider one, each, 

 perhaps, one-tenth to one-twentieth the width of the fore- 

 going. An excellent opportunity was given for an examina- 

 tion of the wood of the trunk, as most of the injured trees had 

 died during the past summer and were removed this fall. In 

 certain trees, such as the elms, where the rings were not so 

 markedly narrower, the cells of the fall wood were almost 

 parenchymatous. 



With the loss of the leaves the entire physiological activity 

 of the tree was deranged. A powerful effort was made by 

 the tree immediately after the storm to produce new leaves, 

 to enable it to carry on the necessary activities. With the 

 loss of the leaves the transpiration current gradually lessened 

 and finally stopped ; the flow of assimilatory compounds 

 ceased and to all intents the plant stopped growing. The 

 root system was practically uninjured, and, in the warm 

 weather of the weeks succeeding the storm, in a ground abun- 

 dantly supplied with water, the activity of the roots must have 

 been a very great one. The rainfall for these months was as 

 follows: May, 9.12 in., June, 4.57 in., July, 4.67 in., August, 

 2.12 in., — as against a normal rainfall of: May, 4.58 in., June, 

 5.08 in., July, 3.76 in., August, 3.50 in. The average mean 

 temperature was, June, 74° F., July, 78.9° F., August 79.4° F. f 

 with an average maximum temperature of: June, 82.6° F., 

 July, 87.6° F., August, 88.7° F. These data show condi- 

 tions very favorable to great root activity. Great volumes 

 of water must have been driven into the trunk, more particu- 

 larly into the new wood. This stimulated the growth of ad- 



