1915] 



MERRILL DISTILLED WATER 475 



cultures 1-4 was about the same in each case, the root growth 

 in Nos. 3 and 4 was much better than that in Nos. 1 and 2, the 

 roots of the former being whiter, cleaner, and having longer 

 and more numerous lateral roots. In the case of those cul- 

 tures grown in distilled water 10 days before removal to full 

 nutrient solution, Nos. 11 and 12 were in somewhat better 

 condition than Nos. 13 and 14, a difference which might 

 readily be expected for the shorter periods in distilled water 

 due to individual variation. After 15 days in distilled water 

 and 18 days in full nutrient solution the benefits derived from 

 renewing the former were markedly evident in the appear- 

 ance of cultures 15-18, even though the actual weights did not 

 show such difference. Nos. 17 and 18 were in better condi- 

 tion than Nos. 15 and 16 respectively, especially as regards 

 the root growth; similarly, Nos. 21 and 22 were in better 

 condition than Nos. 19 and 20 respectively. 



Some special conditions which are of particular interest 

 were observed when the cultures were examined carefully at 

 the close of the experiment. The first point pertains to the 

 method of recovery. After being in the distilled water only 

 one or two days the top growth of such cultures when placed 

 in full nutrient solution proceeds unhindered from the tips 

 of the main stems, i. e., the tips of the stems remain unin- 

 jured and resume growth. But 5 days in distilled water 

 almost marks the limit at which growth can be resumed at 

 the tip of the main axis of the stem when such cultures are 

 subsequently placed in full nutrient solution. After 10 days 

 in distilled water the tips of the stems become injured so 

 that the later growth in full nutrient solution is made from 

 new lateral branches. Hence the period from 5 to 10 days 

 in distilled water before removal to full nutrient solution 

 may be considered a crucial period as regards the recovery 

 and growth of the main stems. 



Another point of interest is the delayed maturity which 

 results in the case of the cultures which are grown for some 

 time in distilled w T ater and later are placed in full nutrient 

 solution. Such plants remain in a green and growing condi- 

 tion much longer than do those which have been in full 



