124 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I40 



it implies a special set of growth-initiating factors that impinge suc- 

 cessfully on the physiological system of the plant only at the start of 

 the season and, once having been counteracted, cannot stimulate that 

 system into growth again until the opening of the next season. Fourth, 

 it implies that growth can slow down to any degree short of a condi- 

 tion producing a sharp outer surface. If a sharp surface is produced 

 it at once becomes the outer surface of an annual increment. Fifth, 

 it implies that, as a result of the fourth impHcation, all so-called 

 doubles are diffuse, never sharp. Sixth, the maximum number of 

 sharply bounded growth layers in a tree reveals the true number of 

 years involved. Finding the age of a tree, or dating specific events, 

 rests, therefore, upon the exact determination of the maximum num- 

 ber of sharply bounded growth layers within the entire plant body, 

 roots, trunk, and branches. The entire plant body is included of neces- 

 sity because in and near the lower forest-border partial growth layers 

 are characteristic and enclose variable areas on the plant body. 



Implications inherent in the idea of multiplicity contrast vividly 

 with those embodied in unity. First, it implies that growth not only 

 can slow down and cease completely within a single season but also 

 can begin anew. Second, the combination of growth factors present 

 at growth initiation in the spring can also be present later during the 

 general growing season. Third, it implies that growth having ceased 

 so completely as to form a sharply bordered growth layer can begin 

 again during the same season. Fourth, it implies that fluctuations in 

 cambial activity and growth processes accompany fluctuations in 

 growth factors. Such activity can be slowed down to various degrees 

 or cease altogether and even though it cease completely, can be reini- 

 tiated the same season. Fifth, it implies that multiplicity and unity are 

 characteristics dependent to a great extent upon environmental condi- 

 tions. Sixth, it implies that the maximum number of sharply bordered 

 growth layers does not represent the true number of years involved — 

 it exaggerates that number. Counting the sharply bordered growth 

 layers, therefore, does not determine the age of a tree and does not 

 date specific events unless the tree grew under conditions where 

 growth factors do not fluctuate in critical amount except once per year 

 and where, therefore, unity is the rule. 



Unity and multiplicity reflect cambial activity, activity which re- 

 sponds to conditions favoring or inhibiting growth. 



If multiplicity exists and if it depends upon environmental condi- 

 tions, it must occur to different degrees. To state the matter from the 

 standpoint of the trees themselves : the ratio of multiple annual incre- 

 ments to single annual increments must vary from region to region 



