157 



this callus is produced from the pith, bark and oamhitira of 

 the split shoot and from it a nm^ camhiu^, which is attached 

 at both sides to the ends of the normal cambium halves (see 

 above p. SO). Similar conditions exist in older branches of 

 woody plants, in which the wood; body is exposed by some In- 

 jury and the thickening ring interrupted. The cambium fur- 

 nishes the above discussed callus and a new oambiiim is pro- 

 duced from it, which attaches itself to the normal one. By 

 means of its capacity for division, the roll lying upon the 

 surface of the injury constantly becomes larger, the cambium 

 produces bark tissue on the outside, wood tissue ob the Inside. 

 This we must term wound-v,rood because of its structure, since 

 it varies from the normal. All possible transitional stages 

 exist betv/een those cases where the new cambium produces normal 

 (or nearly normal) tracheal elements and those in which it pro- 

 duces typical wound -wood. Just as iire found a production of 

 undifferentiated tissue termed callus, not only atthe place of 

 injury Itself, but v^lso at a considerable distance from it in 

 the form of a "Lohden wedge" betv7een the wood and bark, so 

 under the influence of increased stimuli an abnormal wood oc- 

 curs at 350raie distance from the place of injury, near the normal 

 xylera already existing. Although the wood appearing on the 

 wounded surface^ b^ which the exposed places are "covered over", 

 seems to have some especial significance, this seems lacking 

 in the wound-wood of the second kind named. When considering 

 the matter anatomically, we will refer simultaneously to both 

 kiMs of wound -v7ood. 



In the literature on this subject, the investigations of 

 de Vries and Ma,ula come especially under consideration in re- 

 gard to Inquiries concerning life-history and histology-''. Be- 

 sides these, references may be made also the statements on life- 

 history in the preceding chapter and the literature there cited. 



We will consider first of all those wound-wood tissues 

 which roRy be produced developmenta5.1y by the cambium of wounded 

 shoots and root^. 



Histological Composition and Course of the Fibres 



in Wound-wood ' ' ~" 



The deviation of the wound-virood from the normal differs 

 according to Whether its formation is brought hlaout by cross 

 cuts into the cambiian or by longitudinal wounds. The wound 

 wood is characterized in longitudinal wounds by a wide-celled 

 structure and more numerous ducts than under normal conditions. 

 The libriforra fibres are less prominent. 



(175) The action of cross wounds must be described more in de- 

 tail. 



De Vries proved th^t in Caragana arborescens it was possi^ 

 ble to demonstrate the action of wound stimuli on the forma,tion 

 of wound tissue, even at a distance of ycm. from the T/jrpund it- 

 self. The deviation of the wound-wood from the normal becomee 

 less, the more distant its forma-tion from the place ot injury. 

 The difference is the grdatest directly at this place. The 

 cambial cells divide repeatedly as described above, perpendicu- 

 lar to their long axid, thus furnishing only short member ed 

 cells as a result of a continuation of their normD,l tangential 

 activity. The nearer the cambial cells |ire to the place of 



'„ ?• De Vries, Ueb, Wundholz, Flora, X876, Bd. LIX, p» 2. 

 Jfeule, PaserVerlauf im Wundholz. Bibl^ Bot,, 1895, Heft 33. 



