Plate 5 



Fig. I. TTC i-ii-a. Branch section of Cuprcssus arizonica, cut November 24, 

 1945. Xylem of 1938-1945. Bridge between natural frost effects of 1938 and 

 1945 ; partial growth layers ; sharp and diffuse intra-annual growth layers, 

 elsewhere on tlie section all but 2 of the annual increments contain sharp 

 lenses. 



1938: see with thin dw. 

 1939: 2 see, outer dw the stronger; psL. 



1940 : 2 dee ; see. 



1 941 : see with thin dw. 



1942-44: Thin see's wMth tlireadlike dw's. 

 1945 : Frost effects ; see. 



A comparison of this figure with figure 2 (below) and figure i of plate 6, 

 and with figure 2 of plate 6 and figure i of plate 7 gives a study in longi- 

 tudinal continuity along the brancli. 

 Fig. I, pi. 5 — 244 cm. from tip of branch. 

 Fig. 2, pi. 5 and fig. i, pi. 6 — 212.4 cm. from tip of branch. 

 Fig. 2, pi. 6 and fig. i, pi. 7 — 77.5 cm. from tip of branch. 

 Fig. 2. TTC i-ii-b. Portion of branch section 31.6 cm. outward on branch 

 from figure i (above). Xylem of 1941-1945. Absolute dating by means of 

 natural frost effects in 1943, 1944, 1945. Study in circuit uniformity by com- 

 parison with figure i, plate 6 ; and longitudinal uniformity by comparison 

 with figure i (above) and figure 2, plate 6, and figure i, plate 7. 



1 941 : see with incipient ddw. 



1942 : see with ddw ; sL. 



1943 : Natural frost effects ; see with added dw cells. 



1944: Natural frost spots; see. 



1945 : Intense natural frost effects ; see. 



