130 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I40 



increment can be made to yield i, 2, 3, or 4 sharp contacts depending 

 upon the radius selected. 



Text figure 15, XSC i-i-b, has the increment for 1940 only. If 

 different radii are drawn on the figure, it becomes apparent at once 

 not only that great variation exists but also that correlation among the 

 different radial sequences, were they alone available, would be ex- 

 tremely difficult, if not wholly impossible. 



Fig. 2)7 • — TTC 33-13-a. Complete increment for 1942 and a radius extending 

 to the center. 1938: see (as shown) ; 1939: 2 see; 1940: see; 1941 : see; 1942: 

 see with 2 IL's and 4 sL. Multiplicity ; compound and overlapping lenses 

 illustrating variable cambial and growth activities. 



Other examples of different radial sequences on the same cross sec- 

 tion are: text figures 38 (TTAp 2-3-b), 39 (XSC 2-1-b), 40 (XSC 

 2-2-c), 2 (XSC 8-4-a), 3 (XSC 1-4-a), 10 (XSC i-2-a), and 22 

 (XSCi-3-b). 



The section XSC 13-2-a is somewhat of a special case because in 

 the increment for 1938, containing i sce+i msce+i s arc, the sharp 

 portion of the arc lies radially outward from the diffuse part of the 

 msce and overlaps its sharp ends (pi. 33). Thus, by reason of the 



