N. H. COWDRY. 



occurred had the temperature been applied gradually instead of 

 suddenly. 



When heated to a temperature of from 47 to 49 degrees C. for 

 30 minutes the above mentioned granules show a darker stain 

 and appear fewer in number (Fig. 6). Many peculiar, irregular, 

 darkly staining masses may be seen within the nuclei which are 

 difficult to interpret. Controls showed that the tips were all 

 killed, but the remaining portions of the plantlets recovered in a 

 few cases. 



When exposed to a temperature of from 65-73 degrees C. for 

 40 minutes the intensely staining granules become greatly re- 

 duced in number (Fig. 7), the cytoplasm varies greatly in con- 

 sistency and staining reaction, and the nuclei lose all traces of 

 deeply staining nucleoli and granules. None of the controls of 

 the experiment survived. 



In my experience, therefore, plant mitochondria are not ren- 

 dered vesicular through increase in temperature in the same way 

 as the mitochondria in the tissue cultures experimented with by 

 the Lewises ('15). I have also been quite unable to confirm Poli- 

 card's ('12, p. 229) interesting observation that in some glan- 

 dular cells the mitochondria become partly dissolved, when heated 

 to a certain temperature, leaving an unstained residue behind 

 which he believes to represent their albuminous component. Ac- 

 cording to Jost ('07, p. 140), however, albumins proper occur 

 only occasionally in plant cells. 



6. Decreased Temperature. 



Plantlets were exposed to a temperature of n degrees C. in 

 an ordinary ice box for 4 days and preparations were made of 

 their radicles. The cells showed very little change (Fig. 8) ; but 

 it was possible to detect a slight tendency toward clustering of 

 lightly stained filamentous mitochondria in the perinuclear area, 

 and further, that these filaments do not enlarge and stain more 

 intensely than those in other parts of the cytoplasm as they do 

 in normal cells. The experiments which I have already men- 

 tioned on the effect of illumination preclude the possibility of 

 attributing this change in the mitochondria to the darkness of the 

 ice box. 



