J. Smolak 



14:; 



it is often possible to distinguish the healthy from the diseased part 

 by staining alone. The cells with the disorganised content are wont 

 to stain differently from those with the normal content, for instance 

 the disorganised content of the preparations which are stained by 

 Mann's method is obviously of a darker blue than the neighbouring 

 healthy cells. 



The nucleus. The changes in the nuclei which I was able to observe 

 in the mesophyll cells of the diseased leaves are described according 



Figs. 4, 5. Palisade cells with nuclei of amoeboid form. 



Fig. 6. Nucleus from spongy parenchyma showing filamentous projection. 



to their probable developmental stages in the living plant, in so far as 

 it is possible to deduce these from stained preparations. First of all 

 the nuclei become greatly elongated and hypertrophied, their volume 

 is much increased so that they sometimes fill the cell-interior up to 

 the chloroplasts, even touching them (Fig. 2). By this time the surface 

 of the nuclei shows depressions corresponding often to the surface of 

 the nearest chloroplasts (Fig. 3). The nuclei sometimes assume quite 

 an irregular or amoeboid form (Fig. 4) producing lobes which seem 

 to be directed between two neighbouring chloroplasts even when 

 the nuclei do not fill the whole cell-interior (Fig. 5). In other cases the 

 nuclei are seen to produce a long thin projection which is one of the 



