1915] 



MERRILL DISTILLED WATER 491 



true of the other cultures to a certain extent, it no doubt plays 

 a lesser, and real exosmosis a greater, part. 



In connection with the above experiment it was thought 

 desirable to determine whether a difference in the initial tem- 

 perature of the water into which the roots were placed had 

 any immediate or subsequent effect upon the exosmosis from 

 the roots ; plants which had been grown in full nutrient solu- 

 tion for 20 days were used for this purpose. Four cultures 

 were prepared with distilled water at a temperature of 6.5°C, 

 four at 17.2° C, and four at 35.0° C, and conductivity readings 

 were taken after exactly one-half hour, and then at various 

 intervals for 20 days. No attempt was made to keep the water 

 at the initial temperatures and it therefore gradually returned 

 to the temperature of the room. After one-half hour, when 

 the first readings were taken, the respective temperatures 

 were 8.9°C, 16.6°C, and 27.4°C. 



The average conductivities of the water of these cultures 

 are plotted for 20 days in fig. 4, the same units being used as 

 in fig. 3. From these results it may be concluded that the 

 initial differences of temperature can not be said to have 

 exercised much, if any, effect. The results would probably 

 have been different had the temperatures remained at the 

 original point during the 20 days. Wachter ('05) has con- 

 sidered the role of the temperature factor in exosmosis. 



VIII. Discussion and Conclusions 



It is believed that the evidence furnished is sufficient to 

 support the conclusion that pure distilled water per se is not 

 toxic or injurious to plants, and that various other factors 

 enter in to cause the deterioration noted when plants are 

 placed in that medium. 



Of course by qualifying the assertion to include pure dis- 

 tilled water only, we have thus eliminated the effect that may 

 be produced by toxic substances in the distilled water, no 

 matter from whence derived. The abundance of work that 

 has been done on the toxicity of various substances to plant 

 tissues would of course lead us to expect injurious effects if 

 such substances were present in any quantity in the distilled 



