SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 140, NO. 1, PLATE 8 



TTC 3-ii-a. Branch section of Ciiprcssiis ari::ouica. cut April 5, 1941. Xylem of 

 1936-1941. Dating by natural frost effects; single and compound lenses; 

 multiplicity by partial and entire gls ; transition between ddw and sharp 

 lenses ; rhythmic dw. 



1936 : 2 see, inner dw slightly the sharper. 



1937 : psL ; see ; msce ; see with ddw and irregular outer margin. 

 1938: Typical effects of natural frost; psce with sharp, diffuse, and invisible 



margin ; long msL ; see ; short sL. 

 1939: Natural frost spots; see; sharp compound lens. 

 1940: Natural frost spots; see with multiple ddw (or 2 sL's) and irregular 



outer margin ; sL. 

 1941 : inc. lens. 



