573 



considerable amounts of tissue. This young tender overgrowth tissue, as 

 well as the cells bounding the diseased parts of the bark, at once produced 

 thick Itark layers (kn) which completely encased the dead tissue and iso- 

 lated it from the healthy tissue. The hard bast bundles (b) which, in the 

 midst of the healthy bark tissue, became diseased immediately about the 

 wound, had been enclosed by isolated cork circumvallation (Fig. 125 u) so 

 that from them no furtlier decomposition of the surroundmg bark paren- 

 chyma, containing chlorophyll, could take place. 



In the process of healing, the new wood (w h) and the new bark (// r) 

 endeavor to cover the wound, beginning at the sides and extending inward. 



Fig'. 12.5. Frost lioil on a Ijranch of .'^weet clierrj'. Medial section. 



in the centre of the wound, where the gaping edges stand further apart 

 (Fig. 125 n h) no closing has yet been possible. On the other hand, this 

 is the case at the sides. The edges of the two new wood layers (Fig. 126 

 n h and n h' ) have become united and the dead piece of the bark (Fig. 126 w) 

 is separated from the dead piece of the wood. The older and thicker the 

 new wood and bark layers become, the more the dead bark is pushed out- 

 ward and finally pushed off. The dead wood (A p) , of a parenchymatous 

 nature, and the momentarilv fresh wound edges (Fig.. 125 }i p'), likewise 

 formed of parenchyma wood, at first gradually pass over into firmer, normal 

 tissue. The first formed new wood, suitable for circumvallation, bears in 

 itself, in the central wound region, the germ of death; numerous gum 



