von Schrenk — Trees of St. Louis as Influenced by Tornado. 35 



In April, 1896, the normal radial rows of cells were formed 

 until May 27th. They were thin walled and full of sap. 

 After the storm the cambium continued to form cells, but now 

 under the conditions above described. The new cells, highly 

 turgescent, pressed on the cells already formed, and flattened 

 them in many cases (fig. 2, b), into disc-shaped cells. As 

 the cambium cells continued in their growth, with abundant 

 water passing into the new wood, the resulting cells were very 

 much enlarged and much distorted, bearing in no way any 

 resemblance to normal wood. Numerous large spaces or rifts 

 were formed, probably owing to unequal pressure (PI. VI. 

 fig. 2, r). This oedematous wood was formed all around the 

 trunk, and was alike at all points, with a possible variation in 

 thickness on different sides. 



Among the many maples examined there were but few which 

 showed this condition as markedly as this one. This was a 

 disappointment, as it was hoped that the death of so many 

 trees might in some way be connected with this oedematous 

 wood. Its absence in many trees may be ascribed to their 

 greater vigor, and lesser interruption in the transpiration cur- 

 rent. The only other trees with marked oedematous wood 

 were several willows, and in every one of these the malady 

 was very marked. These willows grew near a pond and were 

 close to each other. Two of them had but a trunk and two 

 forks, the others had more branches. It was a surprise to 

 find these willows succumbing to this trouble, and in so 

 marked a manner. The wood of the willow is soft and is 

 composed of very large vessels found in all parts of the 

 wood ring. On PI. VII. fig. 1, such wood is shown, that is to 

 say, a small piece of fall wood followed by spring wood. 

 Fig. 2 is a portion of the wood from the outermost ring of 

 one of these willows. The cells are thin-walled, of very 

 irregular shape, and much compressed in places. The large 

 vessels are in all cases divided into several parenchymatous 

 cells, which in noway resemble the normal vessels (fig. 2, 1). 

 A comparison of figs. 1 and 2 will make this clear. Unfor- 

 tunately these oedematous trees all died during the year, so 

 no opportunity was given to see what would have been the 

 character of the wood, after more normal conditions had set 



