168 



usually larger than those of the phelloderm. It is worth 

 noticipg that even those plants can be capable of forming 

 wound cork which » under normal conditions^ develop no cork 

 on their stalks, (Experiments on Viscura)''-. 



Nearly related, to wound cork is the multicellular tis- 

 sue, which often grows out from the wounded bark on the' 

 places of insert ion of roots and buds. If, for example, 

 Salix branches are placed in water or brought into a room 

 saturated with water vapor, numerous roots develop on them, 

 at the base of which a small, porous, whitish mound of tis- 

 sue is noticeable, which has the greatest similarity to out- 

 growing lentioels, (gompare p. 75). It is oEounf In cross- 

 section thf.t a meristem is produced near the wound in the 

 bark, the derivatives of which resemble elongated colorless 

 balls or seas. Between the individual cells, which are often 

 entirely. detached from one another, lie large intercellular 

 spaces filled with air. Therefore the structures described 

 also histologically atesemble hypertrophied lenticels, Mohl*^ 

 has called attention to this similarity and warned others 

 against confounding the forms. The same tissues are also 

 produced as in the places of insertion of the roots, if buds 

 Injure the tissues of the bark during their development, 

 (fflg. 73). The walls of the wound tissue described do not 

 become cork. 



As far as the conditions are concerns'^, under which 

 wound cork is produced, the relation of its formation to the 

 (187) injury and to the conditions created by it, first come under 

 consideration. Each break in the continuity of the tissue 

 can cause the format ioti of wound cork, no matter if the wound 

 lies on the upper surface, whereby the surrounding air has 

 direct access to it or if "internal" injures are xrmolve^ 

 such as are produced perhaps by twistings of stalks, etc,', 

 A preliminary condition of its production, however, is that 

 at leQst a small degree of transpiration must be possible for 

 the exposed tissue. On this account no wound cork can J>e 

 produced In the sting canals made by parasites which p?:'Oiduce 



falZe, but only oallu^ tissue (hypertrq^phy apd hyperpSM^^ia). 

 n the succulent, juicy gall of Mgrnatus valliamerii upon 

 TChoee Innermof^t tissue voraciousiinhabitants of the gall cav- 

 ity oonotantly graze, a richly outgrowing callus is produced, 

 but wbund-oork only in exceptional cases (in injured galls). 

 Tissues which seem incapable of forming callus, such as the 

 parenchyma of the potato tuber, develop wound-cork after in- 

 jury, only when transpiration is possible. There is no forma- 

 tion of the wound-cork under water ^. Of the many changes in 

 conditions usually caused by injury, apparently the abnormally 

 -•— ^-.--«.- -.-«-_,-«--.-.----.---.----- 



■*■ Bamm, Ueb, d. Bau d, Entwickelungsgeschichte u, d, m«- 

 chan, Eigensch. mehrjfirh, Epidermen beimd, Dikotyl. Beih, z. 

 Bot, Cbl., 1901, Bd, XI, p. 219. 



2 



Quoted above p, 75, note 1, 



^ Compare v. Brefeld, Ueb, Vernarbung u. Blattfall. 

 Pringsheim's Jahrb, f, wiss. Bot,, Bd, XII, p, 133, also 

 above p, 162, note 2, 



^ On the causes of the formation of wound cork, compare 

 also Prank, Krankh, d, Pfl. tZ Aufl,, Bd, I, p, 61 ff, Kny, 

 Uf|b, d, Einfl, V, Druck u, Zug auf die Richtung der Soheide- 

 wande u, s. w. Bef, d, D. Bot, Ges,, 1896, Bd, XIV, p. 378. 



