[Vol. 2 



468 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



from which R' can then be calculated. Having these values, 

 the specific conductivity can be calculated for any determined 

 cell constant (the value of the cell used being .4088). For a 

 fuller discussion see Findlay ('10). 



IV. Recovery of Plants after being in Distilled Water 



for Varying Periods 



The first question studied pertained to the recovery of 

 plants in full nutrient solution after being kept in doubly dis- 

 tilled water for varying periods. To determine the com- 

 parative condition for optimum recovery, the distilled water 

 and the full nutrient medium were renewed every four days 

 in some cultures and left unrenewed in others, in such a way 

 that for either condition of the medium of each set in a cer- 

 tain period the other medium would be both renewed and 

 unrenewed so as to give all possible methods of combination. 

 Examination of table i will make this clear. Thus, for 

 example, with cultures 11, 12, 13, and 14 of the 10-day period 

 in distilled water the doubly distilled water in Nos. 11 and 

 12 was unrenewed ; but when these cultures were placed in full 

 nutrient solution this medium was unchanged or unrenewed 

 for No. 11 and was renewed for No. 12. The distilled water 

 in Nos. 13 and 14 was renewed, and the full nutrient solution 

 unrenewed and renewed respectively. 



In series 1 the small variety of horse beans (Vicia faba) 

 was employed, 8 plants being used to a culture. The condi- 

 tion of the media and duration of growth, the green weight 

 of tops, and the dry weight of tops and roots of series 1 are 

 given in table i. On examining this table it is seen that even 

 after the plants had remained for 20 days in distilled water, 

 they recovered on being placed in the full nutrient solution, 

 while those remaining for 10 days in distilled water produced 

 practically as much growth when later placed in the full 

 nutrient solution as did the plants which were in the latter 



medium during the entire period. 



Of course, as would be expected, the cultures wherein the 

 full nutrient solution was renewed every four days gave much 

 better growth than did those in the unrenewed medium, due, 



