Plate 2 



Fig. I. Con T 2-0-base b i. Trunk section of Pinus tacda, cut May 18, 1944, at 

 17 cm. above ground and 228 cm. below base of terminal bud (146 cm. below 

 base of bud as of December 1939)- Xylem of 1939- 1942. Absolute dating 

 based upon effects of artificial freezing (of April 5, 1940) and date of cutting 

 section ; contrast of densewoods terminating annual increments wbich show 

 great variation in definition. 

 1939: Very weak dw. 



1940: Artificial frost injury and recovery some 8 cells out; outer dw weak, 

 diffuse, almost nonexistent giving complete subsidence of annual 

 character of the "ring." 

 1941 : Outer dw thick, heavy, sharp, striking contrast to outer dws of 1940 



and 1939; outer dw has slight evidence of ddw. 

 1942 : A dee as ilw ; see with wide ddw. 



Fig. 2. Con T 3-0-basc b i. Enlarged portion of figure i (above). Xylem of 

 1939-1941. Artificial frost effects and breakdown of outer marginal definition 

 of annual increment ; absolute dating. 

 1939 : dw weak, subdued, i cell thick. 



1940: 7-10 cells, as reversed sequence, laid down radially by April 5, 1940, 

 when artificial freezing was applied; artificial frost injury and re- 

 covery ; outer dw thin, highly diffuse and essentially nonexistent on 

 some radii. 



Fig. 3. Con T i-i2-a. Branch section of Finns tarda, cut January 16, 1943, from 

 first 1940 tip flush. Xylem of 1940- 1942. Absolute dating by periodic tip- 

 growth measurements ; proved multiplicity by 4 growth layers for 4 tip 

 flushes for 3 years ; normally developed growth layers with tendency toward 

 growth rhythms by ilw's ; densewoods a bit weak ; nuclei visible. 

 1940: 2 see; outer gl with diffuse arcs or ilw. 

 1941 : I see with ilw. 

 1942 : I see with ilw and idw. 



Rhythms expressed by ilw and idw are taken to be incipient departures from 

 strict unitv in the gls of an annual increment. 



