J. Smolak 149 



other (Figs. 18, 19). Or the elongated nucleus shows a simple con- 

 striction (Fig. 20) which may be the beginning of amitosis. The direct 

 division in the plant tissue is, according to the generally accepted view, 

 a characteristic of degeneration or of pathological conditions. I did 

 not succeed in following the fate of the amitotically divided nuclei. 

 Probably they disorganise in the same manner as the nuclei in the 

 uninucleate cells of the diseased area, since in one binucleate palisade 

 cell at least one nucleus showed obvious traces of early disorganisation. 

 In some other attacked cells — as was described above — it can be 

 definitely established that the nucleus becomes more and more deformed, 

 disorganised and finally dies (Fig. 17). 



The chloroplasts. In the diseased area the chloroplasts show remark- 

 able diversity of structure and form, being often very irregular and 

 sometimes destroyed. The beginning of their disorganisation appears 

 as a corrosion of the surface. Their volume is consequently markedly 

 reduced in size and thus in optical section they appear thinner and 

 thinner (Fig. 17). The unusual irregular outlines can be easily observed 

 on the chloroplasts as seen in surface view in a cell uncut by the micro- 

 tome-knife. 



In the strongly affected region the chloroplasts finally appear as 

 very thin scale-like structures, sometimes hardly distinguishable and 

 lying close to the cell walls (Fig. 17). By this time the cell is very 

 often filled with a curious granular substance. In such cells we do 

 not notice any remains of the nuclei. There is no likelihood that the 

 nuclei were removed by the microtome-knife because whole rows of the 

 destroyed cells in such a diseased area do not contain nuclei. Starch 

 grains were never found in the deformed chloroplasts. 



The disorganisation does not progress everywhere in the cells in 

 the same way. In some cells the nucleus appears almost normal or 

 only somewhat hypertrophied, while the chloroplasts may be in an 

 advanced stage of disorganisation. On the contrary we notice cells 

 where the partly disorganised nucleus is found in the cell along with 

 healthy chloroplasts. Yet in most cases the disorganisation progresses 

 equally in the two. 



There can be no question of the changes described being of the nature 

 of artifacts, for in the immediate vicinity of the disorganised cells we 

 can readily observe others with quite healthy contents (Fig. 17). Also 

 the results of autumn changes are here excluded, because all the 

 described cytological modifications appear in leaves fixed not only in 

 October and September but also in those fixed in July. 



