198 N. H. COWDRY. 



as well as under experimental conditions. MacDougal (p. 199) 

 in referring to the living matter of plant cells, says : " Living 

 matter is composed mainly of pentosans and albumins, or albumin 

 derivatives with lipins as a minor component. The proportion 

 of the main components may vary from nearly one hundred per 

 cent, to nearly zero." In reticulate or alveolate protoplasm, mito- 

 chondrial granules are found in the strands of the network or in 

 the more condensed portion of the protoplasm and never in the 

 meshes or alveoli. Filaments, on the other hand, are seen only 

 where the " main components " are intimately mixed and the 

 protoplasm appears to be homogeneous. The differences in 

 chemical constitution, structure of the cell wall and in other par- 

 ticulars, make it difficult to compare the reactions of plant and 

 animal cells to experimentation. 



In reviewing the several experiments it will be seen that mito- 

 chondria are changed to an abnormal degree only under severe 

 conditions which either kill the cell or render its recovery very 

 improbable. Even when the cell has been killed its general ap- 

 pearance varies in almost every case, the mitochondria however 

 are very much reduced in number or disappear entirely by ap- 

 parent solution, or in the case of plasmolysis through the prior 

 appearance of vesicles. 



In the experiments with submergence and restricted air space, 

 where a sufficient supply of oxygen for respiration has not been 

 supplied, the mitochondria are changed in a somewhat similar 

 manner but the location of the changes is reversed. Exposure 

 to the vapors of ether and chloroform produce very different re- 

 sults, and even in cells stimulated by ether vapor or by lecithin, 

 mitochondria are very different in appearance, though increased 

 growth results in both cases. 



I hope in my next paper to make an intensive study of the in- 

 fluence of lecithin upon the mitochondria in plant cells. 



BIBLIOGRAPHY. 

 Beckwith, C. J. 



'14 The Genesis of Plasma-structures in the Egg of Hydractinia echinata. 



Jour. Morph., Vol. 25, pp. 189-252. 

 Busacca, A. 



'15 Sulle modificazione dei plastomi nelle cellule del epitelio pigmentato 



della retina sotto 1'azione dell' luce e dell' oscurita (Tabola n). Ri- 



