STUDIES ON MITOCHONDRIA IN PLANT CELLS. 19! 



for 48 hours. The resulting plasmolysis is illustrated in Fig. 3. 

 It will be noted that the mitochondrial filaments have almost com- 

 pletely disappeared leaving only a comparatively few enlarged 

 spheres, sometimes with faintly staining centers. The vacuoles 

 show no mitochondrial content. None of the control peas sub- 

 jected to the same treatment survived and the assumption is, in 

 agreement with Guilliermond ('18), that the mitochondria en- 

 larged after the death of the cell. 



3. Desiccation. 



Normal plantlets were deprived of water at room temperature 

 for 36 hours, which resulted in considerable shrinkage of the 

 growing root-tips. On examination the cells were found to con- 

 tain for the most part granular, and rather swollen mitochondria 

 (Fig. .4). The vacuolar membrane seems to have disappeared 

 and the protoplasm exhibits great variation in intensity of stain- 

 ing reaction, as do also the contained mitochondria, which in 

 other respects appear to be quite normal. 



4. Illumination. 



Some plantlets were kept in complete darkness, while others of 

 the same age were subjected daily to strong sunlight without 

 affecting in any distinctive way the mitochondrial content of their 

 radicles. It would seem, therefore, that the mitochondria in the 

 cortical cells of the pea radicle are not directly concerned with 

 chemical processes which are accelerated and retarded by varia- 

 tions in illumination. Unfortunately the chlorophyll-containing 

 plumules were not examined. 



5. Increased Temperature. 



Plantlets were heated in a thermostat at various temperatures, 

 care being taken to avoid evaporation. 



The first changes were observed in radicles exposed to a tem- 

 perature of from 43 to 46 degrees C. for 3 hours (Fig. 5). All 

 the filamentous mitochondria disappear and their place is taken 

 by numbers of small faintly staining granules, though a few 

 large and deeply staining spherules may still be seen. It is pos- 

 sible that this segmentation of the mitochondria might not have 



