SI'XTION V. 



WOUNDS. 



CHAPTER XX. 



WOUNDS TO THE AXIAL ORGANS. 



General Discussion. 



However much accidental or intentional injuries to the tree trunk may 

 differ, nevertheless, the process of healing alv^^ays agrees in the essential 

 I)oints. 



We find, in all cases in which the injury to the trunk and branches is so 

 extensive, that the wood body composes part of the wound surface and that 

 both the cambium lying between wood and bark which with undisturbed 

 development makes possible the growth in thickness of the trunk as well as 

 the young tissue elements directly formed from the cambium (which in the 

 following will be included under the term "Cambium"), take over the heal- 

 ing of the wound surface of the mature part of the trunk. In herbaceous 

 stems, or the still herbaceous developmental stages of w^oody trunks and 

 branches other tissue forms can participate in healing the wounds as will be 

 shown later in discussing individual cases under this head. 



The structures of the forms developed from the cambium in the healing 

 of wounds may, however, vary greatly from that of the normal wood ring. 

 The reason for this difference in structure of wound ivood should be sought 

 in the fact that pressure conditions under which the tissue, serving for 

 healing the wound, is produced, are very different from those existing during 

 the formation of the normal wood body. 



Supported by the investigations of G. Kraus, it should be recalled first 

 of all that each trunk and branch has considerable internal tension, due to 

 the difference in growth of its individual tissue forms which are connected 

 with one another. The experiments on tissue tension begun by Hofmeister^, 

 extended by Sachs", and especially fully carried out by Kraus", have proved 



1 Hofmeister, tjber die Beugnng- saftreicher Pflanzenteile durch Erschiitterung. 

 Ber. d. Kg-1. Sachs. Ges. d. Wissensch. 18.59, p. 194. 



2 Sachs, Expei'imentalphysiologie, p. 465-514. 



3 Kraus, Gregor, Die Gewebespannung des Stammes und ihre Folgen. Botan. 

 Zeit, 1867, No, 14. ff. 



