106 LEAF-SCAR [CH. XIII 



has intervened to protect the surface of the scar. The 

 little strand of vascular tissues of the petiole termed 

 leaf- traces, and indicated above by st' which join on to 

 the vascular strands of the shoot-axis st, are commonly 

 narrowed in the regions just referred to, and the apertures 

 of the projecting vessels cut at sep become blocked up. 

 These leaf-trace-scars remain visible, however, long after- 

 wards on the surface of the leaf-scar (see Fig. 59). 



The layer of tissue (Ab) which brings about this 

 process of cutting off or separation of the leaf is termed 

 the absciss-layer, or we may call it simply the separation- 

 layer. The layer of cork (p) which covers over the surface 

 of the scar heals it up as it were is not continued over 

 the base of the bud (6), which is moreover connected by 

 vascular bundles, not shown in the diagram, with the 

 strands st, because this bud has to be supplied with water 

 and food-materials to enable it to grow out next spring. 



We note that this axillary bud, left on the shoot-axis 

 denuded of its leaves in the manner described, stands 

 in definite relation to the leaf-scar, here just above the 

 latter, and although there are variations in the exact 

 position of such buds relative to the leaf-scars, this is 

 the typical condition of affairs. 



