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



These are a few of the types of growth layers as they actually 

 exist in the branches. Synoptic classification is a means to an end; 

 it is an aid to visualizing growth layers in three dimensions. In the 

 matter of marginal definition, transitions occur in all directions. Ap- 

 parently no difference exists outward or inward on a branch as re- 

 gards the incidence — the beginning or ending — of partial growth 

 layers. The same may be said for the trunk as a whole insofar as our 

 work has gone. 



A few examples of longitudinal transitions have been cited pre- 

 viously. Nevertheless, specific examples (tables 5 to 44) are here 

 charted to indicate the nature of growth layers grown under extreme 

 lower forest-border conditions. Only a few out of hundreds are given. 



In all the tables that follow, the figures in centimeters measure the 

 distance of the cross sections from the respective growing tips, the 

 farthest inward being sections a; the vertical succession of growth 

 layers under any one year of a particular section has no relation to the 

 sequence of growth layers in the annual increment ; the sharpest and 

 the best-developed growth layers (i.e., see's) are placed first; and, to 

 the best of our knowledge, a horizontal direction represents continuity 

 or equivalence of the same growth layer outward on the branch. It 

 is to be remarked that the dates given for annual increments have been 

 established with certainty, and no material is included which could 

 have been made uncertain by artificial freezing. If the branches were 

 cut ofif the trees during the growing season, cutting dates are noted at 

 the end of the tables. 



Nearly all tables of this report would be extremely unwieldy with- 

 out the use of abbreviations. These are here listed not only for use 

 with the text but also for use with the plates and figures. 



Abbreviations descriptive of growth layers 



abs absence. 



ce complete, entire growth layer ; contact obscure. 



ct curtain. 



d arc diffuse arc. 



dee diffuse, complete, entire growth layer. 



ddw divided densewood. 



dL diffuse lens. 



dlw divided lightwood. 



d iL diffuse half-lens. 



dw densewood. 



gl growth layer. 



idw interrupted densewood. 



ilw interrupted lightwood. 



inc incomplete, entire growth layer. 



Iw lightwood. 



