NO. I GROWTH LAYERS IN TREE BRANCHES — CLOCK ET AL. I5I 



wood creates a rather unusual phenomenon. Narrowing of cells on 

 the long radius begins far back in the compression wood which itself 

 ceases outward before attaining the outer margin of the growth layer. 

 This outer zone has a translucent appearance and rests halolike on 

 the growth layer. 



The increments for 1936 and 1937 have one tip flush each, for a 

 minimum of two distinct diameter flushes. Such a relationship is 

 taken to be one of the criteria of multiplicity. 



Table S6.—TTP 21-8 

 48 cm. 22 cm. TF 



1st 1936 I see 1 



2nd 1936 I see i see > i 



I dee J 



1st 1937 I see I see 1 



I d arc [ 



2nd 1937 I see i see | 



ddwj 



1938 I msec 1 see 1 



1939 I psee I see i 



I psee 



1940 I see I ce i 



At 22 cm., second 1936 appears to be entirely divided densewood 

 under moderate to high powers of magnification, but under lower 

 power, such as 20X, the appearance is more that of two distinct 

 growth layers. The diffuse arc in first 1937 is simply a tangential row 

 of narrower cells buried in compression wood and better described, 

 perhaps, as interrupted densewood. At 22 cm. the divided dense- 

 wood listed is part of second 1937. The mostly sharp, complete, en- 

 tire growth layer of 1938 at 48 cm. appears diffuse for a short dis- 

 tance, under low power, because the amount of lignification on both 

 sides of the contact is the same. High power resolves the nature of 

 the contact. The increment of 1939 at 48 cm. consists commonly of 

 two to three large cells and one to four narrow. Here and there 

 around the circuit, however, these sizes not only approach each other 

 but approach the sizes of those in contiguous growth layers, a grada- 

 tional feature making recognition of 1939 difficult at those places 

 except under high power. 



The increment for 1939 at 22 cm. contains two entire growth 

 layers, the inner one of which is sharply bordered around the entire 

 circuit. The outer growth layer has an indefinite to diffuse margin 



