BOTANICAL GAZETTE [APRIL 
Discussion 
Another notable feature of the wood of Quercus alba is its 
conspicuously ridged and depressed outline. Cross-sections of the 
twigs: show 5 protruding wedge-shaped segments of secondary 
xylem which include between them 5 narrow, depressed segments, 
separated from the protruding ones by the great lateral leaf trace 
rays. This peculiar formation is especially noticeable in the stems 
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Fics. 17-22.—Figs. 17-19, transverse internodal sections of 3 and 5 year old 
twigs from lower branches of tree III, showing retarded development of multiseriate 
rays; fig. 20, internodal section of 5 year old twig from top branch of tree II; fig. oe: 
section, cut near node, of 5 year old stem from upper branch tree III; fig. 22,.section 
of suppressed 12 year shoot from central region of tree III; striking illustration ~ 
effect of suppressed growth upon medullary ray development; X5.5. 
of shoots 1~10 years old and gradually becomes less prominent in 
the older woods. Barry (2) accounts for this peculiarity of the 
oak wood on the ground that the medullary rays or storage tissue 
associated with the lateral leaf traces have a strong retarding 
influence on the surrounding tissue, thus accounting for the marked 
difference between-the general rate of growth of the woody tissue 
