'242 Relations hctirrt'n Gnnrfli and Envn'onimHt 



•growth can still occur by means of photosynthesis. It a])])ears that eai-ly 

 in life, before the high tide of assimilation is reached, the plant absorbs 

 a relatively large amount of nutrient salts by means of the roots without 

 producing a correspondingly large quantity of dry matter, but as time 

 goes on increasing amounts of dry matter are formed for the same amount 

 of absorbed nitrate. The more favourable the season for assimilation the 

 greater the amount of dry matter ultimately produced per unit of KNO3. 

 as is seen from the fact that for every gram of KNO3 3-91 gms. of dry 

 matter were j)roduced in series N in the summer months against 2-63 gms. 

 in series L in late spring. 



In the changed series K and M a fresh suj)ply of nitrate was added 

 everv week and the results give the measure of absorption and growth 

 for weekly periods, instead of extending over the whole life of the plant 

 to date as in the former case. Under these circumstances it is to be 

 expected that greater irregularity will occur in the figures, as the con- 

 stant changes in environmental conditions will only be averaged up for 

 a week instead of for the whole time of growth. Even so, however, there 

 is some indication, especially in series M (Table II), that as the plant gets 

 older relatively less nitrate is utilised in the production of dry matter, 

 though the evidence is less conclusive than where semi-starvation occurs. 



These results bring out the fact of the relative greater importance 

 of assimilation at the time of heavy growth, when more efficient use is 

 made by the plant of the food material absorbed by the roots. For full 

 information on this point it would be necessary to have a series of 

 analyses of the plant and the nutrient solution at regular intervals in 

 order that the various factors introduced by loss, absorption and as- 

 similation might be examined and correlated. 



Table W (Solutions changed). 



