NO. I GROWTH LAYERS IN TREE BRANCHES — CLOCK ET AL. 279 



All the above applies to growth-layer sequences marked by unity 

 of the annual increment. If some of the annual increments in a se- 

 quence contain multiple growth layers, then surely comparisons be- 

 tween thicknesses of individual growth layers and either annual or pe- 

 riod rainfall chosen at random are wholly invalid. 



The same is true when cycle analysis is performed upon sequences 

 containing multiple growth layers. Perhaps the insertion of multiple 

 growth layers in certain annual increments on a sequence may bear 

 upon discontinuities and phase changes said by some to be character- 

 istic of cycles in tree growth. 



It is quite clear that the factor of multiplicity has an important place 

 in the study of growth cycles in trees, and only where this factor is 

 zero or where allowance is made for its effect, can we hope for fruitful 

 results in the important subject of cycles. 



VII. EXTENSION OF MULTIPLICITY 

 INTO THE TRUNK 



The characteristics of growth layers in branches, especially as con- 

 cern classification and multiplicity, have been described to the extent 

 that present materials permit. The presence of multiplicity has been 

 established by the methods of absolute dating based upon standards of 

 measured exactness. There remains the task of tracing the character- 

 istics found in branches down into the trunk. Although the trunk does 

 not properly come within the scope of this report, mention will be 

 made of the existing evidence. 



Evidence at hand indicates that the types of growth layers and the 

 multiplicity so characteristic of branches continue down into the basal 

 trunk. TTC 12 yielded specimens periodically from 1938 until 1950, 

 when it was felled and dissected. In the winter of 1938-1939, sections 

 were taken from branches, and from the trunk several feet down from 

 the growing point of the leader. Multiplicity was identical in branch 

 and trunk. In the summer of 1950, at the time of complete dissection, 

 trunk sections 84 cm. above the ground showed gross multiplicity 

 within the limits of unstained materials. This was especially true of 

 the interval 1936-1937. 



The incidence of multiplicity has been illustrated and described pre- 

 viously (Clock, 1951) for 1935 in the trunk of the Arizona cypress, 

 TTC 12 ; for 1936-1937, in the trunk of a ponderosa pine; for 1938, 

 in an Arizona cypress; and for 1938- 1948, in a cedar (Deodar cedar) 



