UPWARD TRANSPORT OF NITROGEN 73 



the open for a period of 42 days. The plant in the humid 

 chamber, with a volume of 200 liters, was supplied with 

 a constant flow of 500 liters in 24 hours of air containing 

 some hundredths (" quelques centiemes") of carbon dioxide, 

 while those in the open had only the amount normally 

 present in the air, probably not over 0.03 per cent. He 

 suggests that the high starch content in the humid chamber 

 was due to its accumulation, because metabolism was 

 checked due to a lack of nutrients, and the nutrients were 

 low because transpiration was low. It seems more prob- 

 able that it was due to the excess carbon dioxide, and had 

 nothing to do with transpiration. Furthermore the high 

 silicon, and perhaps also the high chlorine, of the plants 

 in the open may have been due to the dust accumulating 

 on the plants in the open. The high chlorine might also 

 be due to higher light intensity, independent of transpira- 

 tion for, as previously mentioned, Hoagland, Hibbard, and 

 Davis (1926) observed that increased light intensity greatly 

 increased the ability of Nitella cells to accumulate chlorine 

 and other halogens. 



The available evidence indicates rather clearly that 

 nutrient absorption is neither determined nor directly 

 influenced by water absorption, and this seems to be at 

 present rather generally accepted by botanists. That 

 movement after absorption is influenced and determined 

 by transpiration is, however, considered as an established 

 fact by many botanists. The studies on the influence of 

 transpiration on solute absorption, on the other hand, give 

 fairly strong evidence that translocation after absorption 

 does not take place in the transpiration stream. If trans- 

 location does take place with the water in the water-con- 

 ducting tissues and the rate of transport were determined 

 by the rate of transpiration, then the rate of removal from 

 the absorbing organs should be determined in part by the 

 rate of movement of the transpiration stream. MacDougal 

 (1925, p. 28), disagreeing with me on this point, states 

 that ''The rate at which ions enter the root and cross the 

 endodermal membrane is determined by their own ionic 



