STUDIES ON MITOCHONDRIA IN PLANT CELLS. 189 



normal properties of the mitochondria are well known and on 

 account of the fact that the cells are relatively simple, owing to 

 the absence of photosynthesis and extensive starch formation. 

 In view of my failure to find any observations in the literature 

 dealing with the experimental study of mitochondria in plant 

 cells, I have planned my experiments so as to embrace a wide 

 range of conditions in order to be able to define specific prob- 

 lems for further intensive study. 



MATERIAL AND METHODS. 



After the seeds had been sprouted and the plantlets experi- 

 mented with, the radicles were treated by the Regaud formalin- 

 bichromate method, and the sections (cut 4 /A) were stained with 

 iron hematoxylin. It is of the utmost importance to use good 

 and fresh formalin. In order to neutralize the free formic acid, 

 which is so often present, I am in the habit of adding a small 

 amount of magnesium carbonate to the stock solution. Attempts 

 were made to control this method through the observation of 

 living cells supra- vitally stained with janus green without very 

 satisfactory results owing to the difficulty of getting the dye to 

 penetrate the cells. 



Since mitochondria exhibit considerable variations in different 

 parts of the radicle I have confined my observations to the cor- 

 tical cells between the elongating part and the root-cap. Even 

 in this portion, however, neighboring cells occasionally exhibit, 

 without apparent reason, variations in the size, shape and general 

 appearance of the mitochondria, calculated to lead the unwary 

 astray, and the cells near the surface react to experimental con- 

 ditions and to fixation differently from those more deeply placed. 

 It is important, also to bear in mind that mitochondria show a 

 marked and constant regional variation in different parts of 

 single cells so that serial sections are necessary for their study. 



The usual appearance of the mitochondria in the cells under 

 investigation is illustrated in Fig. I. They will be seen to occur 

 in the form of granules, short rods and filaments which show no 

 indication of plast formation. They are distinctly more fila- 

 mentous in the cytoplasm immediately beneath the cell mem- 

 brane than in the region of the nucleus ; this, however, is not so 



