77^ 



and formed the hnnvn, dry edge of tlie wound, recognizable to the naked 

 eye, and thus enclosed each slit (Fig. 173 c). The parenchyma of the inner 

 bark (ir), still capable of increasing, its growth not yet having ended, takes 

 advantage at the edge of the wound of the opportunity of spreading toward 

 each side where the pressure has decreased, that is, over the plane ^ to zv. 

 These cells, therefore, curve outward. Those from the cambial zone shove 

 the first bark cells further out and mature, in the subsequently growing zone, 

 to bark cells (r) containing chlorophyll; and in this way the tender paren- 

 chymatous edge of the wound (r, ir) is primarily produced. The peripheral 

 cells (r) of the convex edge of the wound turn brown later and dry ui*. 



Fig:. 17.'). Overgrowth edg:e produced in a scariHcation wound. 



Cork (k) is produced in the cells lying directly underneath this. This cork 

 zone {k to k), covering the whole wall of the wound, now attaches itself to 

 the outer cork covering of the old bark so that the new structure is sur- 

 rounded by a ver)^ inelastic cork layer which conseciuently presses on the 

 swelling tissue lying beneath it. 



On this account, the bark pressure is also produced at intervals. The 

 influence of this bark pressure on the immediately succeeding products of 

 the cambial zone (c), which is bent forward like a snail but does not reach 

 to the old w^ood (A), manifests itself by the formation of thicker walled ele- 

 ments. New wood (n/i)is produced which toward the wounded side is 



