32 Trans. Acad. Sci. of St. Louis. 



sycamore noted, undoubted traces were found going back 

 for several years, but there was no evidence of the same in 

 the larger branches. The wood taken from the trunks of 

 some thirty maples and sycamores, examined this fall, failed 

 to show any sign of a double ring. These observations agree 

 closely with those made by Kny, who found the double rings 

 in the branches but not in the trunk. If leaf activity and 

 cambial activity stand in any causal relation, it would appear 

 that this is more marked in the younger internodes, where a 

 sudden stoppage in the supply of assimilatory products would 

 be more directly felt than in the trunk. When the leaves 

 stop their activity suddenly, growth in the younger internodes 

 gradually comes to a standstill, to be resumed with renewed 

 leaf activity. It has often been noted, that in those cases, 

 where axillary buds for some reason develop into branches in 

 the same year in which the branch itself develops upon which 

 they are situated, the wood of the parent branch shows no 

 differentiation, probably because the growth was is no way 

 interrupted. From the observations made on the trees of the 

 storm district, it would appear, that interrupted leaf activity 

 on a branch is felt in the younger internodes, causing the 

 formation of an apparent fall wood, which is followed by 

 spring wood when new leaves are formed on that branch, thus 

 giving rise to a double ring. The distance back where this 

 cessation may make itself felt is very variable, depending much 

 upon the position of a branch upon a tree and upon the num- 

 ber of leaves borne by such a branch. 



The study of the wood of the trunk had to be necessarily 

 rather conjectural, for there were absolutely no means of 

 determining positively to what year a certain ring belonged. 

 Under conditions of unfavorable nutrition or stunting, trees 

 such as pines, spruces, etc., form no ring whatever.* With 

 the trees of the storm district the conditions surely were 

 unfavorable enough to warrant the assumption of an entire 

 cessation of growth in the months succeeding the storm. With 

 this fact in mind, it is evident, that the last ring formed 



* Hartig, R. Zur Lehre vom Dickenwachsthum der Waldbaume. Botan- 



ischeZtg. 28: 508. 1870. 



