Gregory : Effects of pressure on roots of Vicia Faba 461 



seem to be affected by the pressure. In one case, I noticed a 

 fragmentation of nucleoli taking place in almost every case, but as 

 this was observed in one series only, it was thought to be due to 

 some other cause than pressure. 



few interesting morphological points were noticed in the 

 changes taking place in the cells of the compressed roots. In all 

 cases, splits or rifts in some stage of formation were seen in the 

 tissues. The beginnings of these splits can be found in the 

 least compressed roots. The first indication of a definite split was 

 the appearance of cells which had lost their entire contents, still 

 retaining, however, their cell walls. These cells were found either 



A 



Figure 3. Displaced periblem cells from region X in figure 2, The cells 

 show the vacuolization of the protoplasm and also the general tendency of the cells to 

 assume their normal condition. X 530- 



in the extreme layer of plerome cells or just within the plerome 

 layer. On either side of this layer were plerome cells in different 

 stages of degeneration. In general, the protoplasm had become 

 vacuolated and had shrunken from the wall. In some cases their 

 nuclei showed signs of abnormality (see figure i). 



In the second group of experiments, which includes the roots 

 that were subjected to a pressure varying from 1000 to 1400 

 grams, the plerome cells were still more vacuolated, and definite 

 splits had appeared not only in the extreme layer of plerome cells 

 but also throughout the central portion. Ev^en with this pressure 

 but {^\x changes were observed in the periblem and dermatogen 

 tissues. 



