Plate 34 



XSC 13-2-b. Branch section 4.5 cm. outward from plate 2ii- Xylem of 1937-1941. 

 Longitudinal variation ; dw with frost effects ; stringers of dw ; "outer thin" 

 gl ; multiplicity. 

 1937 : dee ; see. 

 1938: Frost effects and accompanying dw ; 2 see, with dw of about equal 



weight. 

 1939: 2 see, dw of "outer thin" slightly weaker than inner (compare with 



1940: see whose dw expands into "stringers." 

 1941 : Partly inc. 



Plate 35 



Fig. I. XSJj i-i-a. Branch section of Pinus jcffrcyl, cut June 12, 1940. Xylem 

 of 1937-1940. "Outer thin" gl and dated multiplicity in a pine; two stages of 

 departure from unity : diffuse and sharp intra-annuals ; midincrement cur- 

 tain (or reversed sequence). 

 1937: Faint dee; see with irregular contact. 

 1938: Effects of natural frost; 2 dee resembling reversed sequence with Iw 



in center ; see. 

 1939: 2 see, inner dw stronger than that of the "outer thin" gl (outer thin 



becomes weaker outward on branch). 

 1940: inc. (Branch frozen artificially 15 cm. outward on branch, May 10.) 

 Fig. 2. XSP i-2-a. Branch section of Finns pondcrosa, cut February 22, 1941. 

 Xylem of 1937-1940. Multiplicity in a pine; variation in contact definition. 

 1937 : Faint dee ; see. 

 1938 : Slight frost effects ; see with ddw. 

 1939: dee ; see. 



1940: see with strong, sharply bordered dw ; gl with weak, indefinite, at 

 places nearly invisible dw but resembles outer (or annual) margin 

 of 1939 in plates a, 30, 29; gl (under cambium) with poorly de- 

 veloped or absent dw. 



