101 
THE TREE—ITS SHOOT-SYSTEM 
to side, and therefore stands out like a knife, with an 
upper and a lower edge (fig. 27). 
Now imagine the primary vascular bundles replaced. 
tial longitudinal section of oak wood, 
Fig. 27.—Tange 
cut as they project towards 
’ 
iameters, and showing the transverse sec- 
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The first change is that the cambium in the vascular 
bundles becomes continuous across through the medul- 
