STUDIES ON MITOCHONDRIA IN PLANT CELLS. 197 



mitochondrial appearance. The elongated cells of the periblem 

 are marked by mitochondria differing from those of the younger 

 cells of the same portion. It is impossible to find two rootlets, 

 although growing under precisely similar conditions, in which 

 there is not some difference in the rnitochondrial contents of 

 cells from similar portions. 



We find also that there is much variation in the manner in 

 which mitochondria react to experimental conditions in different 

 parts of the same rootlet and also in rootlets of different stages 

 of growth. The thin, lightly stained filaments, rods and gran- 

 ules are changed by many causes, the granules of older cells are 

 more resistant, and spheres sometimes remain in the protoplasm 

 when all traces of mitochondria have disappeared. 



Segmentation is peculiar to mature filaments and occurs from 

 many causes. It is even an individual variation in plantlets 

 grown under precisely similar conditions. I have seen no indi- 

 cation that the resulting granules elongate to form new filaments 

 or that mitochondria increase through elongation of original 

 granules and the segmentation of the resulting filament. 



Mitochondria normally agglutinate and form lipoidal masses 

 in close proximity to the nucleus. These masses seem to disap- 

 pear and to go into solution in older cells which contain only the 

 persistent granular mitochondria. Scott ('16, p. 249) has also 

 observed agglutination of mitochondria in the cells of the pan- 

 creas of animals poisoned by phosphorus. 



Mention should here be made of the spherical inclusions so 

 commonly seen in the vacuoles of early cortical cells, the origin 

 of which is, in all probability, rnitochondrial. They resemble 

 very closely the spheres in cells at the base of the rootlet which 

 clearly arise from the dissolution of aleurone grains. They 

 both disappear in a similar manner in the median portion of the 

 rootlet, at a distance from their origin. They probably are very 

 similar in composition, for aleurone grains contain all the ele- 

 ments supposed to exist in mitochondria and probably are the 

 source of the continuous supply of the mitochondrial matter sup- 

 plied by the cotyledons. 



The composition and consistency of the protoplasm has some 

 effect on the behavior and appearance of mitochondria in normal 



