178 



11 is wt'U known, tluit Ihc nunibci' of mitosis j^oin<f on 

 williin llu' orj^nnisni in cci'taiii oi<4ans or lissucs. :il ccrlain 

 piTiods oT (i(\('lo|)incnl, is ccMislanl. It would llu rd'oi-c ])v 

 more inuisiial and unc-xpccled if the lissuo cells bcliavecl 

 differently in vitro, (i ii r w i I s e h -") -■"') found an absolute 

 synchronieity loi' the division of cells in organism, in certain 

 synzylia. 



I'^)r ])lanl tissue G. Haberlandl -^'; -*-) has observed 

 similar phenomenons as we have described here. By culti- 

 vation of |)lant tissue cells in xitro. he obserxcd. that single, 

 isolated ])lanl cells were not able to divide, and they showed 

 an absolute tendency for reunition in vitro. These cells were 

 found lo divide only, when they were in contact with, and 

 under the influence of certain other plant tissue elements, 

 the le])tom cells. In the oi)ini()n of Haberlandl, the cell 

 division of i)lant tissue cells should de|)end upon the so- 

 called 'wound-hormons" liberated from the leplom cells in 

 combination with the lesion. Perhaps the leptom cells play 

 the same role for the plants as do the leucocytes for animal 

 organisms. Carrel ^^) found, that the leucocytic secretions 

 contained very active gi'owth-promoting substances. Recently 

 Akamatsu ') showed, that after having made a wound, 

 the plasma from the wounded animal possesses considerably 

 more growth-promoting substances than before the wound 

 was made. 



The preliminary experiments undertaken here, attempting 

 to show that there exists a kind of periodical setting in of 

 cell divisions in the tissue in vitro, must of course be taken 

 with all possible reservation. It would be rather queer 

 it this should not be the case in the explaiited tissue 

 as it seems to be proved with regard to the tissue in 

 vivo, Regaud, Stalfeldt 4«'), Gurwitz 237) _ The fi- 

 gures in the experiments must not be taken too literally; 

 the errors are of course rather gi'oss. It has been extremely 

 difficult to find a suitable technique for tlie elucidation of 

 Ihis problem. At the present time I have determined to 



