156 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I40 



one "sharp, complete, entire" although it appears to be indefinite 

 because of the feeble development of the light wood immediately to 

 the outside. On unstained sections under very low magnifications 

 the outer boundary of 1937 appears to be diffuse. Examination of 

 stained sections under the microscope shows that the densewood of 

 1937 is definite and the boundary sharp but obscured by severe frost 

 injury almost at the start of 1938. 



42 cm. 



193s I see 



1st 1936 I see 



2nd 1936 I see 



I dee 



1st 1937 I see 



2nd 1937 I see 



1938 I dee 



1939 I msce 



1940 I msec 



1941 I msec 



I pcL 



The outer contact of 1938 is made obscure by the subnormal devel- 

 opment of 1939. At first sight, at 42 cm., and under very low powers, 

 1939 is a concurrent lens of two members. Under higher powers, the 

 lightwood only of 1939 is lenticular, the densewood, two cells thick, 

 lying flush against the densewood of 1938 and continuing between 

 the cusps of the "lenses." Lightwood is lenticular, densewood entire. 

 At 30 cm. the resolution of 1939 requires high power on stained sec- 

 tions, but even so, one would remain in doubt if he did not have 

 other branches from the same tree available for study. The incre- 

 ment at 20 cm. is an excellent example of divided densewood con- 

 stituting total annual growth. The densewood of 1939 lies immedi- 

 ately against that of 1938 over most of the circuit ; where it does not 

 do so, the insertion of partially developed lightwood cells makes 1939 

 visible under low power for half the extent of those cells. It is an 

 interesting point to note that one of the "lenses" of 1939 carries a 

 natural frost injury. 



The apparent, as against the actual, occurrence of 1939 brings out 

 a possible contrast in interpretations. Under very low power the 



