146 



if kept in moist air, a glittering crystalline covering is 

 formed from the callus tissue, which, in comparison with the 

 new formations already described, does not exceed a relative- 

 ly moderate amount, The cells, lying under the cut surface, 

 are stretched perpendicular to the surface of the wound and 

 divide repeatedly with irregularly oriented walls. Rows of 

 cells belonging together developmentally generally are not 

 formed here. I observed at times v. predominant tangential 

 division In the hark of young Sambuous sprouts. 



To be sure the j)ith often Increases but only rarely fur- 

 nishes rolls of tisfiue"as large as those on cuttings of Popu- 

 lus. In these from 10 to 12 days after the Injury, a sheath- ' 

 like knobbed callus mass, usually star ^shaped, becomes visible, 

 above the pith and is often greatly increased; the wounded star- 

 face of th« xylem grows out toward the crmbium like a vvall and 

 is united to it, , It Is clear from longitudinal sections that 

 the uppermoBt cell-layers of the pith died after the Injury and 

 that those inKnedlately Underneath have been elongated perpen- 

 dicularly to the wounded surface and ho.ve divided repeatedly. 

 JProm the very beginning any definite direction of division is 

 also absent here;- generally well arranged cell rov;s do not 

 e3!;lst. 



The epideriglg becomes active only In rare cases. Stoll 

 thinks it doubtful if it can ever participate in the formation 

 of callus, Hansen observed divisions in the epidermis, how- 

 ever » which led to callus formation (Begonia), Further obser- 

 vations are reported by Ifessart, who proved a division of the 

 epidermal cells in the stalks of Ricinus and Tinanthia floe, 

 cit.)-'- 



Any ability to form callus may scarcely be spokem of in 

 connection with the cells of the wo od -par ench^ona , As was 

 thoroughly discussed above, the wood parenchyma cells, incited 

 to growth through injury, almost alv/ays remain undivided. Ac- 

 cording to Molisch, division is known only in the tyloses of 

 (IB3\) Guspldaria pterocarpg and Robinia (compare above p. 102), This 

 does not exclude the fact that tyloses occasionally become en- 

 larged and^ like the products of the cambium, the bark, etc. 

 can curve dut over the cut surfadp.. In the cuttings of Pla- 

 * tanus the cells grow Out ffom th© isut ducts in the form of 

 gigantic pouches. The statements &t Stoll jfchat in Passi flora 



f uadranRularl^ the tyloses grow out only from the ducts, and 

 ivide repeatedly outside these, producing a many celled callus, 

 which unites with the callus of the cambium and of the pltb, 

 are baaed Indeed upon an error ftnd need testing. Tompa^s*^ 

 study throws light on the participation of the wood parenchyma 



1 Hansen, Vgl. Unters, Sb. Adventivbildung bel d. Pfl. 

 Abhandl. Senchenberg Naturforsoh. Ges. 1881, Bd. XII,- Massart, 

 Cicatrisation chez 1, v^g^taux. MAm, cour. etc. Acad. Belgi- 

 que, 1898, T. IVH, - I must here l®ave.cpen the question as 



to wbether in the cases given by Massart, callus tissue or 

 wound-cork is really concerned, we will discuss these again 

 later. In the case investigated by Bretfeld (Ueb. Vernarbung 

 und Blattfall, Pringsheim's Jahrb. f. wlss, Bot. 1/380, Bd.XII, 

 p. 1^3), In which theepldermal cells of the Cllvi{i leaf divided, 

 a -formp.tion of cork exists as the author eraphasl*es; perhaps 

 similarly also In the cell division observed by JJassart on 

 the leaf of Banioterla argentea (loc, cit,, p. 49^, 



2 Soudoure de la greffeherbacee de la vigne, Ann. Inst, 

 Ampelol. Budapest 1900,. T. 1, ^p, I, 



