28 Trans. Acad. Sci. of St. Louis. 



all their leaves, and in every one new leaves were formed 

 from the buds on the twigs of that year. In the spring of 

 1897, all the trees which had survived the winter, continued 

 to grow normally from the buds formed on the adventitious 

 shoots. Numerous sections of branches were made early in 

 May to determine the character of the wood formed by the 

 trees during the previous summer. Such sections were made 

 again in the fall (1897) of wood taken from trees which had 

 died during the summer, as well as from living trees. 



The contention that more than one ring of wood may be 

 formed in one year is one of long stauding, and much has 

 been written both for and against it. Cotta* found that 

 where trees had been injured by insects or frost, such trees 

 made little or no growth subsequent to the injury, and where 

 they did, the new wood did not differ from that previously 

 formed. On the other hand, a very dry period following a 

 spring very favorable to rapid growth, caused a stoppage 

 in the activity of the cambium, which then formed fall wood. 

 A good rain started new activity, spring wood resulted, and 

 thus two rings were visible. Sometimes the two rings could 

 be seen on one side only. Unger,f in a discussion as to 

 whether the development of several generations of buds in 

 any way influences the growth of annual rings, concludes that 

 there is no causal relation, both being due to changing con- 

 ditions of temperature and moisture. He found but one or 

 two species where there were any signs of double rings. A 

 full discussion of the earlier views is presented by Kny.f 

 He had occasion to study this problem near Berlin on some 

 trees defoliated by caterpillars. In several trees of Tilia 

 parvijlora the leaves were destroyed early in the year, aud in 

 July the buds formed for the following year developed. Kny 

 was able to determine positively the presence of two distinct 

 rings of wood as a result of premature development of these 



* Cotta, H. Naturbeobachtungen tiber die Bewegurig u. Funktion des 

 Saftes etc. 75. Weimar 1806. 



t Unger, F. Uber den Grund der Bildung der Jahreslagen dicotyler 

 Holzpflanzen. Bot. Ztg. 5: 265. 1847. 



X Kny, L. Uber die Verdoppelung des Jahresringes. Verhandl. d. Bot. 

 Ver. d. Prov. Brandenburg 21 : 185. pi. 1. 1879. 



