J. Smolak 151 



nuclei means the beginning of a reaction and we cannot decide whether 

 it is response to the increased metabolism only or to the influence of a 

 toxic substance. 



Concerning the amitotic mode of division the most recent view is 

 that it is not a phenomenon that appears in healthy tissues unless the 

 latter are old {e.g. the well-known case of amitosis in the old cells of 

 Cham) or degenerate. Many cases of apparent amitosis have been 

 explained as modified stages of mitosis (Nemec, 10). There are, indeed, 

 authors who state that even in wound tissue the mitotic mode of division 

 regularly takes place (Strasburger, 19, p. 22). On the contrary we 

 often meet with amitosis in the hypertrophied tissue of galls although 

 even in the latter karyokinesis occurs (Kiister, 7, p. 200). Amitosis 

 was observed by Guttenberg in Capsella bursa- pastoris after infection 

 by Cystopus (Albugo) candidus, and by Shibata in P odocar pus -ga\\s, 

 etc. (Kiister, 7, p. 200). Amitotic mode of division — so far as is known 

 — is never followed by cell division, so that bi- or multinucleate cells 

 result. The few cases of amitosis in the silvered Prunus leaves are 

 what one would expect in the organs attacked by such a serious disease 

 ("der Milchglanz sei ein absolut sicherer Vorlaufer des Todes eines 

 Zweiges," Sorauer, 17, p. 285), where the conditions leading to hyper- 

 trophy prevail. Amitosis here is evidently similar to amitosis in galls. 

 The few binucleate palisade cells observed are probably in respect of 

 their origin the result of amitosis. 



Some modifications in the cell and nucleus resembling the condition 

 found in Prunus leaves have been often brought about by artificial 

 methods. Thus, for example, twenty years ago Klemm (5) investigated 

 the phenomena of disorganisation in the hairs of Urtica, Momordica, 

 Tradescantia and Trianea caused by abnormal conditions of tempera- 

 ture, light, electrical action and the influence of acids. In his ex- 

 periments marked changes in the protoplast appeared particularly in 

 response to electrical action. The nuclei became elongated or in other 

 ways deformed and finally destroyed. The granular appearance of the 

 nuclei changes to a homogeneous (" ein glasiges homogenes Aussehen," 

 p. 688) and the nucleus later collapses completely just as happens in 

 some cases in the silvered leaves (Fig. 17). Otherwise in Klemm's 

 experiments "der Kern erleidet bei der Desorganisation der Zelle all- 

 gemein wenig sichtbare Veranderungen" (p. 686). Several years later 

 Nemec (10) obtained interesting modifications of nuclei by the influence 

 of chloralhydrate, some cases of which resemble these in the diseased 

 Prunus leaves. 



