von Schrenlc — Trees of St. Louis as Influenced by Tornado. 29 



buds. He determined furthermore that the presence of two 

 rings was evident for several years back, and gradually became 

 obliterated, varying in different branches. The phenomenon 

 was a variable one in other respects, for the two rings did not 

 always occur even in branches from which all the leaves had 

 been removed. He proved the presence of two rings in Sor- 

 bus aucuparia and Quercus pedunculala. Fagus silvatica 

 var. pendula, which had lost all its leaves, and where a second 

 growth took place, did not form a second ring. Kny suggests 

 at the end of his account, that to prove the relationship be- 

 tween defoliation and wood formation a number of trees 

 ought to be entirely defoliated, and the resulting changes 

 studied. 



Acting upon this suggestion, Wilhelm* removed the leaves 

 from some trees of Quercus sessiliflora on June 7, and from 

 several others on July 9. Incisions were made in the trunks 

 to study the wood formation. The same was done for a 

 series of control trees of similar age and thickness. In the 

 fall the trees were cut down and examined. A double ring 

 was found, but only on the side of the tree on which the 

 incisions had been made, both in the defoliated and control 

 trees. The youngest ring was characterized by lesser width, 

 and a sudden decrease in the size of the vessels in the center 

 of the ring. The differences were not great enough to warrant 

 the conclusion that a distinct double ring had been formed. 

 He concludes by saying: " The appearance is accordingly a 

 result of injury to the woody cylinder, and is much furthered 

 by defoliation. " He found the abnormal growth of wood in 

 the trunk, but no sign of it in the branches, an observation 

 directly opposed to that of Kny. Those trees defoliated in 

 July showed no interruption in the woody ring, although all 

 had produced a second growth of leaves. 



The formation of double rings of wood in Pinus sp., owing 

 to late spring frosts, has been shown by Hartigf and others. 

 Hartig found branches which had been frozen repeatedly for 



* Wilhelm, K. Die Verdoppelung des Jahresringes. Ber. d. d. bot. 

 Gesell. 1: 216. 1883. 



t Hartig, R. Doppelringe.in Folge van Spiitfrost. Forstlich naturwiss. 

 Zeltschrif t 4 : 1. 1895. 



