Plate i8 



Fig. I. TTP 3^-6-a. Branch section of Pinits pondrrosa. cut November ii, 1944. 



Xylem of 1943-1944. Incipient intraseasonal growth fluctuation; transition 



between idw and ilw. 



1943 : Normal see, with suggestion of growth fluctuation. 



1944: idw or ilw as incipient multiplicity. 

 Fig. 2. 'FTP 24-2-a. Branch section of Piiiiis piuidrrosa. cut November 29, 1941. 



Xylem of 1937-1941. Separation and accentuation of the "double," or intra- 



annual gl, of 1940 contrasted with that of 1938; irregular margin under 



cambium. 



1937: see. 



1938 : Frost efifects ; tendency toward wide ddw. 



1939: see. 



1940 : Frost spots ; s to d gl ; see. 



1941 : dee and an entire band of added growth (psg) with very irregular 

 margin, reentrants filled with nucleated cells. 



