NO. I GROWTH LAYERS IN TREE BRANCHES — CLOCK ET AL. 3I 



surrounding a measured branch and comparison with the latter, as 

 well as general observations on the entire tree in comparison with the 

 same single branch ; second, short-interval, close observations of indi- 

 vidual branches, information on which was recorded by successive 

 diagrams and by notes ; and third, general observations on the condi- 

 tions of the vegetation from the beginning of leafing out and initia- 

 tion of tip growth until the following winter. 



In some respects, observations as described above give a better 

 picture of what a tree as a whole is doing than measurements of a 

 single branch; this is especially true of the relationship among dif- 

 ferent branches and among different trees as regards initiation of 

 growth, decrease in growth rate, actual intraseasonal halts, and the 

 final setting of winter buds. 



It is clear, of course, that growth layers formed in tip flushes which 

 have been measured periodically are thereby dated with exactness. 

 These growth layers can be followed inward on the branch by means 

 of a series of sections. 



NUMBER OF DIAMETER FLUSHES IN RELATION TO NUMBER OF 

 TIP FLUSHES 



At once three possibilities become obvious, namely : ( i ) The num- 

 ber of diameter flushes equals the number of tip flushes, (2) the 

 number of diameter flushes exceeds the number of tip flushes, and 

 (3) the number of diameter flushes falls short of the number of tip 

 flushes. 



The first case represents very probably the normal situation, 

 wherein a single diameter flush corresponds to each tip flush. If 

 the single tip flush constitutes a single year's growth and extends from 

 the terminal bud scale scars at the base of a former terminal bud 

 to the bud scale scars at the base of the next outer terminal bud, then 

 the corresponding diameter flush is an annual growth layer. If the 

 actual dates of formation of tip-growth increments are unknown, we 

 make no presumption of multiplicity in a one-to-one correspondence 

 of diameter and tip flushes. 



The second case is held to be clear proof of multiplicity because 

 the maximum length of time involved in the formation of one tip 

 flush is one full growing season. Two diameter flushes in a single 

 tip flush represent the minimum amount of multiplicity over an 

 annual interval. Should tip flushes themselves be multiple within a 

 year, the multiplicity of growth layers is correspondingly increased. 



The third case probably requires more than one tip flush in a 

 season and does not necessarily concern the problems of multiplicity. 



