Plate i6 



Fig. I. TTJ 3-4-a. Branch section of JiDiipcnis viryhiiana, cut January i, 1943. 



Xylem of 1937-1942. Sharp arc; transition between an entire gl and a lens; 



short diffuse incipient lens. 



1937 : see, with outer margin made irregular by "added on," highly lignified 

 cells. 



1938: Slight effects of frost injury and parenchyma circle; see. 



1939: Parenchyma circle and dw cells; rhythmic densewood ; dee; see. 



1940 : see ; "outer thin" see whose dw is entire and whose Iw is entire except 

 over a few degrees. 



1941 : s arc ; short dL, closer to being a lens than ddw ; see. 



1942: Faint dL's ; sL; see. 

 Fig. 2. TTP 20-6-a. Branch section of Finns pondcrosa, cut February i, 1941. 



Xylem of 1939-1940. Irregular and immature xylem under the cambium; 



single to double row of dw cells as ilw in midst of annual increment. 



1939 : see with irregular outer contact. 



1940: Iw apparently terminated by ilw, which is followed by poorly de- 

 veloped dw ; irregular and immature outer border. Actually ilw (or 

 idw) is outer dw of an msce, and the poorly developed dw outside 

 the ilw is an inc L. 



