Oct. IS, 1919 Relation of Nutrient Medium to Plant Absorption 91 



results are given by the different concentrations. In the lowest concen- 

 tration the percentage of water transpired is much less than the percentage 

 of electrolytes absorbed. In the highest concentration this relation is 

 reversed, and in the intermediate concentration of 0.32 atmospheres the 

 two percentages are essentially the same. It is quite clear that absorp- 

 tion may proceed independently of transpiration, and that the plant 

 may absorb and transpire at such rates as either to increase or decrease 

 the concentration of the nutrient solution. This is in general agreement 

 with the views of Pantanelli {32). 



WATER CULTURES, SERIES 2 



This series was planned for the purpose of making certain observations 

 on absorption and growth when plants were grown to maturity. Two- 

 liter bottles were used, and only one plant was placed in each bottle. The 

 experiment was started on February 11. During the first 10 weeks, 

 up to the time of heading out, a solution of 0.78 atmospheres concentra- 

 tion was used, the solution being changed about once each v/eek. The 

 composition of the solution was similar to that used in sand cultures, 

 series 2. The plants were grown out of doors, and at this season the 

 growth rate was fairly slow. On April 27 the plants were divided into 

 3 groups of 10 plants each and the solution changed to 3 different con- 

 centrations, o.io, 0.30, and 0.80 atmospheres, respectively. Thereafter 

 the solutions were not changed. The object of this procedure was to gain 

 some insight into the growth and absorption of the plant when the 

 concentration of the solution was diminished during the latter part of 

 the growth cycle, a condition somewhat analogous to that in the soil. 



The plants completed the growth cycle and produced matured heads. 

 There were from 5 to 10 tillers on each plant. Most of the heads were 

 out by May 17, and by June 24 the hard dough stage was reached. 

 The plants were cut July 16, about five months after planting. A 

 marked difference in appearance was noted in the three groups. Although 

 water was, of course, not a limiting factor in the concentration of o.io 

 atmospheres, the plants turned yellow sooner and more completely than 

 in the higher concentrations. In the highest concentration considerable 

 green color persisted to the end of the experiment, but the heads from 

 the lowest concentration were slightly superior. In the highest concen- 

 tration the ripening was slow and there was some indication of shrinkage 

 of the grain before the period of desiccation. The total yields as shown 

 below are greater in the higher concentrations, although there is no 

 significant difference between the concentrations of o.io and 0.30 or 0.80 

 atmospheres, for the yield of heads and even the difference in the yields 

 of stems and leaves are not necessarily significant. 



