MITOCHONDRIA IN PLANT AND ANIMAL CELLS. 221 



tribution of mitochondria is unaltered by centrifuging, as Key 

 discovered. But this is no reason to believe that these mito- 

 chondria differ from others in their specific gravity. At any 

 rate, where the method is applicable (i. e., in egg cells) the 

 mitochondria are heavier than protoplasm, in which respect 

 they conform to what we know of phosphatids and differ sharply 

 from oils and neutral fats which rise to the surface and float, 

 instead of being thrown down. 



6. In some animal cells mitochondria act as solutes for different 

 substances. Pigments of various kinds are frequently found dis- 

 solved in their substance so that they assume the most brilliant 

 hues. Asvadourova ('13, p. 263), following Prenant, calls them 

 "chromochondria" on this account. The presence of droplets 

 of neutral fat within the mitochondrial filaments has also been 

 recorded. 



Plant mitochondria behave in exactly the same way, antho- 

 cyanin, chlorophyll and other pigments, sugar, starch and even 

 fat being heaped up within them (Guilliermond, '136, p. 647). 



7. There seems to be a certain correspondence between varia- 

 tions in the histological picture of mitochondria and variations 

 in the phospholipin content of the same organ on chemical 

 analysis. Thus Mayer, Rathery and Schaeffer ('14, p. 612) 

 have been able to alter the mitochondria experimentally in liver 

 cells. In stages with more mitochondrial substance, chemical 

 analyses show an increase in phosphorized lipoid ; in stages with 

 less, diminution. 



Unfortunately mitochondria in plant cells have not been 

 investigated from this point of view. 



8. And, finally, the very interesting observations of Russo and 

 Rene Van der Stricht must be mentioned. Russo ('12, p. 215) 

 claims to have been able to increase the number of mitochondria 

 in the oocytes of the fowl by the injection of lecithin and Rene 

 Van der Stricht ('n, p. 435) obtained results which seemed to be 

 confirmatory. 



Since there have been no observations along this line in plant 

 cells I have attacked the problem by growing peas in solutions 

 of lecithin. The results were in no sense definite and concise, 

 though the mitochondria did seem to be increased in diameter. 



